1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com 2 * Copyright (c) 2016 Facebook 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of version 2 of the GNU General Public 6 * License as published by the Free Software Foundation. 7 * 8 * This program is distributed in the hope that it will be useful, but 9 * WITHOUT ANY WARRANTY; without even the implied warranty of 10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 11 * General Public License for more details. 12 */ 13 #include <linux/kernel.h> 14 #include <linux/types.h> 15 #include <linux/slab.h> 16 #include <linux/bpf.h> 17 #include <linux/bpf_verifier.h> 18 #include <linux/filter.h> 19 #include <net/netlink.h> 20 #include <linux/file.h> 21 #include <linux/vmalloc.h> 22 #include <linux/stringify.h> 23 24 /* bpf_check() is a static code analyzer that walks eBPF program 25 * instruction by instruction and updates register/stack state. 26 * All paths of conditional branches are analyzed until 'bpf_exit' insn. 27 * 28 * The first pass is depth-first-search to check that the program is a DAG. 29 * It rejects the following programs: 30 * - larger than BPF_MAXINSNS insns 31 * - if loop is present (detected via back-edge) 32 * - unreachable insns exist (shouldn't be a forest. program = one function) 33 * - out of bounds or malformed jumps 34 * The second pass is all possible path descent from the 1st insn. 35 * Since it's analyzing all pathes through the program, the length of the 36 * analysis is limited to 64k insn, which may be hit even if total number of 37 * insn is less then 4K, but there are too many branches that change stack/regs. 38 * Number of 'branches to be analyzed' is limited to 1k 39 * 40 * On entry to each instruction, each register has a type, and the instruction 41 * changes the types of the registers depending on instruction semantics. 42 * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is 43 * copied to R1. 44 * 45 * All registers are 64-bit. 46 * R0 - return register 47 * R1-R5 argument passing registers 48 * R6-R9 callee saved registers 49 * R10 - frame pointer read-only 50 * 51 * At the start of BPF program the register R1 contains a pointer to bpf_context 52 * and has type PTR_TO_CTX. 53 * 54 * Verifier tracks arithmetic operations on pointers in case: 55 * BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), 56 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20), 57 * 1st insn copies R10 (which has FRAME_PTR) type into R1 58 * and 2nd arithmetic instruction is pattern matched to recognize 59 * that it wants to construct a pointer to some element within stack. 60 * So after 2nd insn, the register R1 has type PTR_TO_STACK 61 * (and -20 constant is saved for further stack bounds checking). 62 * Meaning that this reg is a pointer to stack plus known immediate constant. 63 * 64 * Most of the time the registers have UNKNOWN_VALUE type, which 65 * means the register has some value, but it's not a valid pointer. 66 * (like pointer plus pointer becomes UNKNOWN_VALUE type) 67 * 68 * When verifier sees load or store instructions the type of base register 69 * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, FRAME_PTR. These are three pointer 70 * types recognized by check_mem_access() function. 71 * 72 * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value' 73 * and the range of [ptr, ptr + map's value_size) is accessible. 74 * 75 * registers used to pass values to function calls are checked against 76 * function argument constraints. 77 * 78 * ARG_PTR_TO_MAP_KEY is one of such argument constraints. 79 * It means that the register type passed to this function must be 80 * PTR_TO_STACK and it will be used inside the function as 81 * 'pointer to map element key' 82 * 83 * For example the argument constraints for bpf_map_lookup_elem(): 84 * .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, 85 * .arg1_type = ARG_CONST_MAP_PTR, 86 * .arg2_type = ARG_PTR_TO_MAP_KEY, 87 * 88 * ret_type says that this function returns 'pointer to map elem value or null' 89 * function expects 1st argument to be a const pointer to 'struct bpf_map' and 90 * 2nd argument should be a pointer to stack, which will be used inside 91 * the helper function as a pointer to map element key. 92 * 93 * On the kernel side the helper function looks like: 94 * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) 95 * { 96 * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1; 97 * void *key = (void *) (unsigned long) r2; 98 * void *value; 99 * 100 * here kernel can access 'key' and 'map' pointers safely, knowing that 101 * [key, key + map->key_size) bytes are valid and were initialized on 102 * the stack of eBPF program. 103 * } 104 * 105 * Corresponding eBPF program may look like: 106 * BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR 107 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK 108 * BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP 109 * BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), 110 * here verifier looks at prototype of map_lookup_elem() and sees: 111 * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok, 112 * Now verifier knows that this map has key of R1->map_ptr->key_size bytes 113 * 114 * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far, 115 * Now verifier checks that [R2, R2 + map's key_size) are within stack limits 116 * and were initialized prior to this call. 117 * If it's ok, then verifier allows this BPF_CALL insn and looks at 118 * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets 119 * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function 120 * returns ether pointer to map value or NULL. 121 * 122 * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off' 123 * insn, the register holding that pointer in the true branch changes state to 124 * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false 125 * branch. See check_cond_jmp_op(). 126 * 127 * After the call R0 is set to return type of the function and registers R1-R5 128 * are set to NOT_INIT to indicate that they are no longer readable. 129 */ 130 131 /* verifier_state + insn_idx are pushed to stack when branch is encountered */ 132 struct bpf_verifier_stack_elem { 133 /* verifer state is 'st' 134 * before processing instruction 'insn_idx' 135 * and after processing instruction 'prev_insn_idx' 136 */ 137 struct bpf_verifier_state st; 138 int insn_idx; 139 int prev_insn_idx; 140 struct bpf_verifier_stack_elem *next; 141 }; 142 143 #define BPF_COMPLEXITY_LIMIT_INSNS 98304 144 #define BPF_COMPLEXITY_LIMIT_STACK 1024 145 146 #define BPF_MAP_PTR_POISON ((void *)0xeB9F + POISON_POINTER_DELTA) 147 148 struct bpf_call_arg_meta { 149 struct bpf_map *map_ptr; 150 bool raw_mode; 151 bool pkt_access; 152 int regno; 153 int access_size; 154 }; 155 156 /* verbose verifier prints what it's seeing 157 * bpf_check() is called under lock, so no race to access these global vars 158 */ 159 static u32 log_level, log_size, log_len; 160 static char *log_buf; 161 162 static DEFINE_MUTEX(bpf_verifier_lock); 163 164 /* log_level controls verbosity level of eBPF verifier. 165 * verbose() is used to dump the verification trace to the log, so the user 166 * can figure out what's wrong with the program 167 */ 168 static __printf(1, 2) void verbose(const char *fmt, ...) 169 { 170 va_list args; 171 172 if (log_level == 0 || log_len >= log_size - 1) 173 return; 174 175 va_start(args, fmt); 176 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args); 177 va_end(args); 178 } 179 180 /* string representation of 'enum bpf_reg_type' */ 181 static const char * const reg_type_str[] = { 182 [NOT_INIT] = "?", 183 [UNKNOWN_VALUE] = "inv", 184 [PTR_TO_CTX] = "ctx", 185 [CONST_PTR_TO_MAP] = "map_ptr", 186 [PTR_TO_MAP_VALUE] = "map_value", 187 [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null", 188 [PTR_TO_MAP_VALUE_ADJ] = "map_value_adj", 189 [FRAME_PTR] = "fp", 190 [PTR_TO_STACK] = "fp", 191 [CONST_IMM] = "imm", 192 [PTR_TO_PACKET] = "pkt", 193 [PTR_TO_PACKET_END] = "pkt_end", 194 }; 195 196 #define __BPF_FUNC_STR_FN(x) [BPF_FUNC_ ## x] = __stringify(bpf_ ## x) 197 static const char * const func_id_str[] = { 198 __BPF_FUNC_MAPPER(__BPF_FUNC_STR_FN) 199 }; 200 #undef __BPF_FUNC_STR_FN 201 202 static const char *func_id_name(int id) 203 { 204 BUILD_BUG_ON(ARRAY_SIZE(func_id_str) != __BPF_FUNC_MAX_ID); 205 206 if (id >= 0 && id < __BPF_FUNC_MAX_ID && func_id_str[id]) 207 return func_id_str[id]; 208 else 209 return "unknown"; 210 } 211 212 static void print_verifier_state(struct bpf_verifier_state *state) 213 { 214 struct bpf_reg_state *reg; 215 enum bpf_reg_type t; 216 int i; 217 218 for (i = 0; i < MAX_BPF_REG; i++) { 219 reg = &state->regs[i]; 220 t = reg->type; 221 if (t == NOT_INIT) 222 continue; 223 verbose(" R%d=%s", i, reg_type_str[t]); 224 if (t == CONST_IMM || t == PTR_TO_STACK) 225 verbose("%lld", reg->imm); 226 else if (t == PTR_TO_PACKET) 227 verbose("(id=%d,off=%d,r=%d)", 228 reg->id, reg->off, reg->range); 229 else if (t == UNKNOWN_VALUE && reg->imm) 230 verbose("%lld", reg->imm); 231 else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE || 232 t == PTR_TO_MAP_VALUE_OR_NULL || 233 t == PTR_TO_MAP_VALUE_ADJ) 234 verbose("(ks=%d,vs=%d,id=%u)", 235 reg->map_ptr->key_size, 236 reg->map_ptr->value_size, 237 reg->id); 238 if (reg->min_value != BPF_REGISTER_MIN_RANGE) 239 verbose(",min_value=%lld", 240 (long long)reg->min_value); 241 if (reg->max_value != BPF_REGISTER_MAX_RANGE) 242 verbose(",max_value=%llu", 243 (unsigned long long)reg->max_value); 244 if (reg->min_align) 245 verbose(",min_align=%u", reg->min_align); 246 if (reg->aux_off) 247 verbose(",aux_off=%u", reg->aux_off); 248 if (reg->aux_off_align) 249 verbose(",aux_off_align=%u", reg->aux_off_align); 250 } 251 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 252 if (state->stack_slot_type[i] == STACK_SPILL) 253 verbose(" fp%d=%s", -MAX_BPF_STACK + i, 254 reg_type_str[state->spilled_regs[i / BPF_REG_SIZE].type]); 255 } 256 verbose("\n"); 257 } 258 259 static const char *const bpf_class_string[] = { 260 [BPF_LD] = "ld", 261 [BPF_LDX] = "ldx", 262 [BPF_ST] = "st", 263 [BPF_STX] = "stx", 264 [BPF_ALU] = "alu", 265 [BPF_JMP] = "jmp", 266 [BPF_RET] = "BUG", 267 [BPF_ALU64] = "alu64", 268 }; 269 270 static const char *const bpf_alu_string[16] = { 271 [BPF_ADD >> 4] = "+=", 272 [BPF_SUB >> 4] = "-=", 273 [BPF_MUL >> 4] = "*=", 274 [BPF_DIV >> 4] = "/=", 275 [BPF_OR >> 4] = "|=", 276 [BPF_AND >> 4] = "&=", 277 [BPF_LSH >> 4] = "<<=", 278 [BPF_RSH >> 4] = ">>=", 279 [BPF_NEG >> 4] = "neg", 280 [BPF_MOD >> 4] = "%=", 281 [BPF_XOR >> 4] = "^=", 282 [BPF_MOV >> 4] = "=", 283 [BPF_ARSH >> 4] = "s>>=", 284 [BPF_END >> 4] = "endian", 285 }; 286 287 static const char *const bpf_ldst_string[] = { 288 [BPF_W >> 3] = "u32", 289 [BPF_H >> 3] = "u16", 290 [BPF_B >> 3] = "u8", 291 [BPF_DW >> 3] = "u64", 292 }; 293 294 static const char *const bpf_jmp_string[16] = { 295 [BPF_JA >> 4] = "jmp", 296 [BPF_JEQ >> 4] = "==", 297 [BPF_JGT >> 4] = ">", 298 [BPF_JGE >> 4] = ">=", 299 [BPF_JSET >> 4] = "&", 300 [BPF_JNE >> 4] = "!=", 301 [BPF_JSGT >> 4] = "s>", 302 [BPF_JSGE >> 4] = "s>=", 303 [BPF_CALL >> 4] = "call", 304 [BPF_EXIT >> 4] = "exit", 305 }; 306 307 static void print_bpf_insn(const struct bpf_verifier_env *env, 308 const struct bpf_insn *insn) 309 { 310 u8 class = BPF_CLASS(insn->code); 311 312 if (class == BPF_ALU || class == BPF_ALU64) { 313 if (BPF_SRC(insn->code) == BPF_X) 314 verbose("(%02x) %sr%d %s %sr%d\n", 315 insn->code, class == BPF_ALU ? "(u32) " : "", 316 insn->dst_reg, 317 bpf_alu_string[BPF_OP(insn->code) >> 4], 318 class == BPF_ALU ? "(u32) " : "", 319 insn->src_reg); 320 else 321 verbose("(%02x) %sr%d %s %s%d\n", 322 insn->code, class == BPF_ALU ? "(u32) " : "", 323 insn->dst_reg, 324 bpf_alu_string[BPF_OP(insn->code) >> 4], 325 class == BPF_ALU ? "(u32) " : "", 326 insn->imm); 327 } else if (class == BPF_STX) { 328 if (BPF_MODE(insn->code) == BPF_MEM) 329 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n", 330 insn->code, 331 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 332 insn->dst_reg, 333 insn->off, insn->src_reg); 334 else if (BPF_MODE(insn->code) == BPF_XADD) 335 verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n", 336 insn->code, 337 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 338 insn->dst_reg, insn->off, 339 insn->src_reg); 340 else 341 verbose("BUG_%02x\n", insn->code); 342 } else if (class == BPF_ST) { 343 if (BPF_MODE(insn->code) != BPF_MEM) { 344 verbose("BUG_st_%02x\n", insn->code); 345 return; 346 } 347 verbose("(%02x) *(%s *)(r%d %+d) = %d\n", 348 insn->code, 349 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 350 insn->dst_reg, 351 insn->off, insn->imm); 352 } else if (class == BPF_LDX) { 353 if (BPF_MODE(insn->code) != BPF_MEM) { 354 verbose("BUG_ldx_%02x\n", insn->code); 355 return; 356 } 357 verbose("(%02x) r%d = *(%s *)(r%d %+d)\n", 358 insn->code, insn->dst_reg, 359 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 360 insn->src_reg, insn->off); 361 } else if (class == BPF_LD) { 362 if (BPF_MODE(insn->code) == BPF_ABS) { 363 verbose("(%02x) r0 = *(%s *)skb[%d]\n", 364 insn->code, 365 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 366 insn->imm); 367 } else if (BPF_MODE(insn->code) == BPF_IND) { 368 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n", 369 insn->code, 370 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 371 insn->src_reg, insn->imm); 372 } else if (BPF_MODE(insn->code) == BPF_IMM && 373 BPF_SIZE(insn->code) == BPF_DW) { 374 /* At this point, we already made sure that the second 375 * part of the ldimm64 insn is accessible. 376 */ 377 u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm; 378 bool map_ptr = insn->src_reg == BPF_PSEUDO_MAP_FD; 379 380 if (map_ptr && !env->allow_ptr_leaks) 381 imm = 0; 382 383 verbose("(%02x) r%d = 0x%llx\n", insn->code, 384 insn->dst_reg, (unsigned long long)imm); 385 } else { 386 verbose("BUG_ld_%02x\n", insn->code); 387 return; 388 } 389 } else if (class == BPF_JMP) { 390 u8 opcode = BPF_OP(insn->code); 391 392 if (opcode == BPF_CALL) { 393 verbose("(%02x) call %s#%d\n", insn->code, 394 func_id_name(insn->imm), insn->imm); 395 } else if (insn->code == (BPF_JMP | BPF_JA)) { 396 verbose("(%02x) goto pc%+d\n", 397 insn->code, insn->off); 398 } else if (insn->code == (BPF_JMP | BPF_EXIT)) { 399 verbose("(%02x) exit\n", insn->code); 400 } else if (BPF_SRC(insn->code) == BPF_X) { 401 verbose("(%02x) if r%d %s r%d goto pc%+d\n", 402 insn->code, insn->dst_reg, 403 bpf_jmp_string[BPF_OP(insn->code) >> 4], 404 insn->src_reg, insn->off); 405 } else { 406 verbose("(%02x) if r%d %s 0x%x goto pc%+d\n", 407 insn->code, insn->dst_reg, 408 bpf_jmp_string[BPF_OP(insn->code) >> 4], 409 insn->imm, insn->off); 410 } 411 } else { 412 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]); 413 } 414 } 415 416 static int pop_stack(struct bpf_verifier_env *env, int *prev_insn_idx) 417 { 418 struct bpf_verifier_stack_elem *elem; 419 int insn_idx; 420 421 if (env->head == NULL) 422 return -1; 423 424 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state)); 425 insn_idx = env->head->insn_idx; 426 if (prev_insn_idx) 427 *prev_insn_idx = env->head->prev_insn_idx; 428 elem = env->head->next; 429 kfree(env->head); 430 env->head = elem; 431 env->stack_size--; 432 return insn_idx; 433 } 434 435 static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env, 436 int insn_idx, int prev_insn_idx) 437 { 438 struct bpf_verifier_stack_elem *elem; 439 440 elem = kmalloc(sizeof(struct bpf_verifier_stack_elem), GFP_KERNEL); 441 if (!elem) 442 goto err; 443 444 memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state)); 445 elem->insn_idx = insn_idx; 446 elem->prev_insn_idx = prev_insn_idx; 447 elem->next = env->head; 448 env->head = elem; 449 env->stack_size++; 450 if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) { 451 verbose("BPF program is too complex\n"); 452 goto err; 453 } 454 return &elem->st; 455 err: 456 /* pop all elements and return */ 457 while (pop_stack(env, NULL) >= 0); 458 return NULL; 459 } 460 461 #define CALLER_SAVED_REGS 6 462 static const int caller_saved[CALLER_SAVED_REGS] = { 463 BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5 464 }; 465 466 static void init_reg_state(struct bpf_reg_state *regs) 467 { 468 int i; 469 470 for (i = 0; i < MAX_BPF_REG; i++) { 471 regs[i].type = NOT_INIT; 472 regs[i].imm = 0; 473 regs[i].min_value = BPF_REGISTER_MIN_RANGE; 474 regs[i].max_value = BPF_REGISTER_MAX_RANGE; 475 regs[i].min_align = 0; 476 regs[i].aux_off = 0; 477 regs[i].aux_off_align = 0; 478 } 479 480 /* frame pointer */ 481 regs[BPF_REG_FP].type = FRAME_PTR; 482 483 /* 1st arg to a function */ 484 regs[BPF_REG_1].type = PTR_TO_CTX; 485 } 486 487 static void __mark_reg_unknown_value(struct bpf_reg_state *regs, u32 regno) 488 { 489 regs[regno].type = UNKNOWN_VALUE; 490 regs[regno].id = 0; 491 regs[regno].imm = 0; 492 } 493 494 static void mark_reg_unknown_value(struct bpf_reg_state *regs, u32 regno) 495 { 496 BUG_ON(regno >= MAX_BPF_REG); 497 __mark_reg_unknown_value(regs, regno); 498 } 499 500 static void reset_reg_range_values(struct bpf_reg_state *regs, u32 regno) 501 { 502 regs[regno].min_value = BPF_REGISTER_MIN_RANGE; 503 regs[regno].max_value = BPF_REGISTER_MAX_RANGE; 504 regs[regno].min_align = 0; 505 } 506 507 static void mark_reg_unknown_value_and_range(struct bpf_reg_state *regs, 508 u32 regno) 509 { 510 mark_reg_unknown_value(regs, regno); 511 reset_reg_range_values(regs, regno); 512 } 513 514 enum reg_arg_type { 515 SRC_OP, /* register is used as source operand */ 516 DST_OP, /* register is used as destination operand */ 517 DST_OP_NO_MARK /* same as above, check only, don't mark */ 518 }; 519 520 static int check_reg_arg(struct bpf_reg_state *regs, u32 regno, 521 enum reg_arg_type t) 522 { 523 if (regno >= MAX_BPF_REG) { 524 verbose("R%d is invalid\n", regno); 525 return -EINVAL; 526 } 527 528 if (t == SRC_OP) { 529 /* check whether register used as source operand can be read */ 530 if (regs[regno].type == NOT_INIT) { 531 verbose("R%d !read_ok\n", regno); 532 return -EACCES; 533 } 534 } else { 535 /* check whether register used as dest operand can be written to */ 536 if (regno == BPF_REG_FP) { 537 verbose("frame pointer is read only\n"); 538 return -EACCES; 539 } 540 if (t == DST_OP) 541 mark_reg_unknown_value(regs, regno); 542 } 543 return 0; 544 } 545 546 static int bpf_size_to_bytes(int bpf_size) 547 { 548 if (bpf_size == BPF_W) 549 return 4; 550 else if (bpf_size == BPF_H) 551 return 2; 552 else if (bpf_size == BPF_B) 553 return 1; 554 else if (bpf_size == BPF_DW) 555 return 8; 556 else 557 return -EINVAL; 558 } 559 560 static bool is_spillable_regtype(enum bpf_reg_type type) 561 { 562 switch (type) { 563 case PTR_TO_MAP_VALUE: 564 case PTR_TO_MAP_VALUE_OR_NULL: 565 case PTR_TO_MAP_VALUE_ADJ: 566 case PTR_TO_STACK: 567 case PTR_TO_CTX: 568 case PTR_TO_PACKET: 569 case PTR_TO_PACKET_END: 570 case FRAME_PTR: 571 case CONST_PTR_TO_MAP: 572 return true; 573 default: 574 return false; 575 } 576 } 577 578 /* check_stack_read/write functions track spill/fill of registers, 579 * stack boundary and alignment are checked in check_mem_access() 580 */ 581 static int check_stack_write(struct bpf_verifier_state *state, int off, 582 int size, int value_regno) 583 { 584 int i; 585 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0, 586 * so it's aligned access and [off, off + size) are within stack limits 587 */ 588 589 if (value_regno >= 0 && 590 is_spillable_regtype(state->regs[value_regno].type)) { 591 592 /* register containing pointer is being spilled into stack */ 593 if (size != BPF_REG_SIZE) { 594 verbose("invalid size of register spill\n"); 595 return -EACCES; 596 } 597 598 /* save register state */ 599 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = 600 state->regs[value_regno]; 601 602 for (i = 0; i < BPF_REG_SIZE; i++) 603 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL; 604 } else { 605 /* regular write of data into stack */ 606 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = 607 (struct bpf_reg_state) {}; 608 609 for (i = 0; i < size; i++) 610 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC; 611 } 612 return 0; 613 } 614 615 static int check_stack_read(struct bpf_verifier_state *state, int off, int size, 616 int value_regno) 617 { 618 u8 *slot_type; 619 int i; 620 621 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off]; 622 623 if (slot_type[0] == STACK_SPILL) { 624 if (size != BPF_REG_SIZE) { 625 verbose("invalid size of register spill\n"); 626 return -EACCES; 627 } 628 for (i = 1; i < BPF_REG_SIZE; i++) { 629 if (slot_type[i] != STACK_SPILL) { 630 verbose("corrupted spill memory\n"); 631 return -EACCES; 632 } 633 } 634 635 if (value_regno >= 0) 636 /* restore register state from stack */ 637 state->regs[value_regno] = 638 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE]; 639 return 0; 640 } else { 641 for (i = 0; i < size; i++) { 642 if (slot_type[i] != STACK_MISC) { 643 verbose("invalid read from stack off %d+%d size %d\n", 644 off, i, size); 645 return -EACCES; 646 } 647 } 648 if (value_regno >= 0) 649 /* have read misc data from the stack */ 650 mark_reg_unknown_value_and_range(state->regs, 651 value_regno); 652 return 0; 653 } 654 } 655 656 /* check read/write into map element returned by bpf_map_lookup_elem() */ 657 static int check_map_access(struct bpf_verifier_env *env, u32 regno, int off, 658 int size) 659 { 660 struct bpf_map *map = env->cur_state.regs[regno].map_ptr; 661 662 if (off < 0 || size <= 0 || off + size > map->value_size) { 663 verbose("invalid access to map value, value_size=%d off=%d size=%d\n", 664 map->value_size, off, size); 665 return -EACCES; 666 } 667 return 0; 668 } 669 670 /* check read/write into an adjusted map element */ 671 static int check_map_access_adj(struct bpf_verifier_env *env, u32 regno, 672 int off, int size) 673 { 674 struct bpf_verifier_state *state = &env->cur_state; 675 struct bpf_reg_state *reg = &state->regs[regno]; 676 int err; 677 678 /* We adjusted the register to this map value, so we 679 * need to change off and size to min_value and max_value 680 * respectively to make sure our theoretical access will be 681 * safe. 682 */ 683 if (log_level) 684 print_verifier_state(state); 685 env->varlen_map_value_access = true; 686 /* The minimum value is only important with signed 687 * comparisons where we can't assume the floor of a 688 * value is 0. If we are using signed variables for our 689 * index'es we need to make sure that whatever we use 690 * will have a set floor within our range. 691 */ 692 if (reg->min_value < 0) { 693 verbose("R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n", 694 regno); 695 return -EACCES; 696 } 697 err = check_map_access(env, regno, reg->min_value + off, size); 698 if (err) { 699 verbose("R%d min value is outside of the array range\n", 700 regno); 701 return err; 702 } 703 704 /* If we haven't set a max value then we need to bail 705 * since we can't be sure we won't do bad things. 706 */ 707 if (reg->max_value == BPF_REGISTER_MAX_RANGE) { 708 verbose("R%d unbounded memory access, make sure to bounds check any array access into a map\n", 709 regno); 710 return -EACCES; 711 } 712 return check_map_access(env, regno, reg->max_value + off, size); 713 } 714 715 #define MAX_PACKET_OFF 0xffff 716 717 static bool may_access_direct_pkt_data(struct bpf_verifier_env *env, 718 const struct bpf_call_arg_meta *meta, 719 enum bpf_access_type t) 720 { 721 switch (env->prog->type) { 722 case BPF_PROG_TYPE_LWT_IN: 723 case BPF_PROG_TYPE_LWT_OUT: 724 /* dst_input() and dst_output() can't write for now */ 725 if (t == BPF_WRITE) 726 return false; 727 /* fallthrough */ 728 case BPF_PROG_TYPE_SCHED_CLS: 729 case BPF_PROG_TYPE_SCHED_ACT: 730 case BPF_PROG_TYPE_XDP: 731 case BPF_PROG_TYPE_LWT_XMIT: 732 if (meta) 733 return meta->pkt_access; 734 735 env->seen_direct_write = true; 736 return true; 737 default: 738 return false; 739 } 740 } 741 742 static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off, 743 int size) 744 { 745 struct bpf_reg_state *regs = env->cur_state.regs; 746 struct bpf_reg_state *reg = ®s[regno]; 747 748 off += reg->off; 749 if (off < 0 || size <= 0 || off + size > reg->range) { 750 verbose("invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n", 751 off, size, regno, reg->id, reg->off, reg->range); 752 return -EACCES; 753 } 754 return 0; 755 } 756 757 /* check access to 'struct bpf_context' fields */ 758 static int check_ctx_access(struct bpf_verifier_env *env, int off, int size, 759 enum bpf_access_type t, enum bpf_reg_type *reg_type) 760 { 761 /* for analyzer ctx accesses are already validated and converted */ 762 if (env->analyzer_ops) 763 return 0; 764 765 if (env->prog->aux->ops->is_valid_access && 766 env->prog->aux->ops->is_valid_access(off, size, t, reg_type)) { 767 /* remember the offset of last byte accessed in ctx */ 768 if (env->prog->aux->max_ctx_offset < off + size) 769 env->prog->aux->max_ctx_offset = off + size; 770 return 0; 771 } 772 773 verbose("invalid bpf_context access off=%d size=%d\n", off, size); 774 return -EACCES; 775 } 776 777 static bool is_pointer_value(struct bpf_verifier_env *env, int regno) 778 { 779 if (env->allow_ptr_leaks) 780 return false; 781 782 switch (env->cur_state.regs[regno].type) { 783 case UNKNOWN_VALUE: 784 case CONST_IMM: 785 return false; 786 default: 787 return true; 788 } 789 } 790 791 static int check_pkt_ptr_alignment(const struct bpf_reg_state *reg, 792 int off, int size, bool strict) 793 { 794 int ip_align; 795 int reg_off; 796 797 /* Byte size accesses are always allowed. */ 798 if (!strict || size == 1) 799 return 0; 800 801 reg_off = reg->off; 802 if (reg->id) { 803 if (reg->aux_off_align % size) { 804 verbose("Packet access is only %u byte aligned, %d byte access not allowed\n", 805 reg->aux_off_align, size); 806 return -EACCES; 807 } 808 reg_off += reg->aux_off; 809 } 810 811 /* For platforms that do not have a Kconfig enabling 812 * CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS the value of 813 * NET_IP_ALIGN is universally set to '2'. And on platforms 814 * that do set CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, we get 815 * to this code only in strict mode where we want to emulate 816 * the NET_IP_ALIGN==2 checking. Therefore use an 817 * unconditional IP align value of '2'. 818 */ 819 ip_align = 2; 820 if ((ip_align + reg_off + off) % size != 0) { 821 verbose("misaligned packet access off %d+%d+%d size %d\n", 822 ip_align, reg_off, off, size); 823 return -EACCES; 824 } 825 826 return 0; 827 } 828 829 static int check_val_ptr_alignment(const struct bpf_reg_state *reg, 830 int size, bool strict) 831 { 832 if (strict && size != 1) { 833 verbose("Unknown alignment. Only byte-sized access allowed in value access.\n"); 834 return -EACCES; 835 } 836 837 return 0; 838 } 839 840 static int check_ptr_alignment(struct bpf_verifier_env *env, 841 const struct bpf_reg_state *reg, 842 int off, int size) 843 { 844 bool strict = env->strict_alignment; 845 846 if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) 847 strict = true; 848 849 switch (reg->type) { 850 case PTR_TO_PACKET: 851 return check_pkt_ptr_alignment(reg, off, size, strict); 852 case PTR_TO_MAP_VALUE_ADJ: 853 return check_val_ptr_alignment(reg, size, strict); 854 default: 855 if (off % size != 0) { 856 verbose("misaligned access off %d size %d\n", 857 off, size); 858 return -EACCES; 859 } 860 861 return 0; 862 } 863 } 864 865 /* check whether memory at (regno + off) is accessible for t = (read | write) 866 * if t==write, value_regno is a register which value is stored into memory 867 * if t==read, value_regno is a register which will receive the value from memory 868 * if t==write && value_regno==-1, some unknown value is stored into memory 869 * if t==read && value_regno==-1, don't care what we read from memory 870 */ 871 static int check_mem_access(struct bpf_verifier_env *env, u32 regno, int off, 872 int bpf_size, enum bpf_access_type t, 873 int value_regno) 874 { 875 struct bpf_verifier_state *state = &env->cur_state; 876 struct bpf_reg_state *reg = &state->regs[regno]; 877 int size, err = 0; 878 879 if (reg->type == PTR_TO_STACK) 880 off += reg->imm; 881 882 size = bpf_size_to_bytes(bpf_size); 883 if (size < 0) 884 return size; 885 886 err = check_ptr_alignment(env, reg, off, size); 887 if (err) 888 return err; 889 890 if (reg->type == PTR_TO_MAP_VALUE || 891 reg->type == PTR_TO_MAP_VALUE_ADJ) { 892 if (t == BPF_WRITE && value_regno >= 0 && 893 is_pointer_value(env, value_regno)) { 894 verbose("R%d leaks addr into map\n", value_regno); 895 return -EACCES; 896 } 897 898 if (reg->type == PTR_TO_MAP_VALUE_ADJ) 899 err = check_map_access_adj(env, regno, off, size); 900 else 901 err = check_map_access(env, regno, off, size); 902 if (!err && t == BPF_READ && value_regno >= 0) 903 mark_reg_unknown_value_and_range(state->regs, 904 value_regno); 905 906 } else if (reg->type == PTR_TO_CTX) { 907 enum bpf_reg_type reg_type = UNKNOWN_VALUE; 908 909 if (t == BPF_WRITE && value_regno >= 0 && 910 is_pointer_value(env, value_regno)) { 911 verbose("R%d leaks addr into ctx\n", value_regno); 912 return -EACCES; 913 } 914 err = check_ctx_access(env, off, size, t, ®_type); 915 if (!err && t == BPF_READ && value_regno >= 0) { 916 mark_reg_unknown_value_and_range(state->regs, 917 value_regno); 918 /* note that reg.[id|off|range] == 0 */ 919 state->regs[value_regno].type = reg_type; 920 state->regs[value_regno].aux_off = 0; 921 state->regs[value_regno].aux_off_align = 0; 922 } 923 924 } else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) { 925 if (off >= 0 || off < -MAX_BPF_STACK) { 926 verbose("invalid stack off=%d size=%d\n", off, size); 927 return -EACCES; 928 } 929 if (t == BPF_WRITE) { 930 if (!env->allow_ptr_leaks && 931 state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL && 932 size != BPF_REG_SIZE) { 933 verbose("attempt to corrupt spilled pointer on stack\n"); 934 return -EACCES; 935 } 936 err = check_stack_write(state, off, size, value_regno); 937 } else { 938 err = check_stack_read(state, off, size, value_regno); 939 } 940 } else if (state->regs[regno].type == PTR_TO_PACKET) { 941 if (t == BPF_WRITE && !may_access_direct_pkt_data(env, NULL, t)) { 942 verbose("cannot write into packet\n"); 943 return -EACCES; 944 } 945 if (t == BPF_WRITE && value_regno >= 0 && 946 is_pointer_value(env, value_regno)) { 947 verbose("R%d leaks addr into packet\n", value_regno); 948 return -EACCES; 949 } 950 err = check_packet_access(env, regno, off, size); 951 if (!err && t == BPF_READ && value_regno >= 0) 952 mark_reg_unknown_value_and_range(state->regs, 953 value_regno); 954 } else { 955 verbose("R%d invalid mem access '%s'\n", 956 regno, reg_type_str[reg->type]); 957 return -EACCES; 958 } 959 960 if (!err && size <= 2 && value_regno >= 0 && env->allow_ptr_leaks && 961 state->regs[value_regno].type == UNKNOWN_VALUE) { 962 /* 1 or 2 byte load zero-extends, determine the number of 963 * zero upper bits. Not doing it fo 4 byte load, since 964 * such values cannot be added to ptr_to_packet anyway. 965 */ 966 state->regs[value_regno].imm = 64 - size * 8; 967 } 968 return err; 969 } 970 971 static int check_xadd(struct bpf_verifier_env *env, struct bpf_insn *insn) 972 { 973 struct bpf_reg_state *regs = env->cur_state.regs; 974 int err; 975 976 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) || 977 insn->imm != 0) { 978 verbose("BPF_XADD uses reserved fields\n"); 979 return -EINVAL; 980 } 981 982 /* check src1 operand */ 983 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 984 if (err) 985 return err; 986 987 /* check src2 operand */ 988 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 989 if (err) 990 return err; 991 992 /* check whether atomic_add can read the memory */ 993 err = check_mem_access(env, insn->dst_reg, insn->off, 994 BPF_SIZE(insn->code), BPF_READ, -1); 995 if (err) 996 return err; 997 998 /* check whether atomic_add can write into the same memory */ 999 return check_mem_access(env, insn->dst_reg, insn->off, 1000 BPF_SIZE(insn->code), BPF_WRITE, -1); 1001 } 1002 1003 /* when register 'regno' is passed into function that will read 'access_size' 1004 * bytes from that pointer, make sure that it's within stack boundary 1005 * and all elements of stack are initialized 1006 */ 1007 static int check_stack_boundary(struct bpf_verifier_env *env, int regno, 1008 int access_size, bool zero_size_allowed, 1009 struct bpf_call_arg_meta *meta) 1010 { 1011 struct bpf_verifier_state *state = &env->cur_state; 1012 struct bpf_reg_state *regs = state->regs; 1013 int off, i; 1014 1015 if (regs[regno].type != PTR_TO_STACK) { 1016 if (zero_size_allowed && access_size == 0 && 1017 regs[regno].type == CONST_IMM && 1018 regs[regno].imm == 0) 1019 return 0; 1020 1021 verbose("R%d type=%s expected=%s\n", regno, 1022 reg_type_str[regs[regno].type], 1023 reg_type_str[PTR_TO_STACK]); 1024 return -EACCES; 1025 } 1026 1027 off = regs[regno].imm; 1028 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 || 1029 access_size <= 0) { 1030 verbose("invalid stack type R%d off=%d access_size=%d\n", 1031 regno, off, access_size); 1032 return -EACCES; 1033 } 1034 1035 if (meta && meta->raw_mode) { 1036 meta->access_size = access_size; 1037 meta->regno = regno; 1038 return 0; 1039 } 1040 1041 for (i = 0; i < access_size; i++) { 1042 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) { 1043 verbose("invalid indirect read from stack off %d+%d size %d\n", 1044 off, i, access_size); 1045 return -EACCES; 1046 } 1047 } 1048 return 0; 1049 } 1050 1051 static int check_helper_mem_access(struct bpf_verifier_env *env, int regno, 1052 int access_size, bool zero_size_allowed, 1053 struct bpf_call_arg_meta *meta) 1054 { 1055 struct bpf_reg_state *regs = env->cur_state.regs; 1056 1057 switch (regs[regno].type) { 1058 case PTR_TO_PACKET: 1059 return check_packet_access(env, regno, 0, access_size); 1060 case PTR_TO_MAP_VALUE: 1061 return check_map_access(env, regno, 0, access_size); 1062 case PTR_TO_MAP_VALUE_ADJ: 1063 return check_map_access_adj(env, regno, 0, access_size); 1064 default: /* const_imm|ptr_to_stack or invalid ptr */ 1065 return check_stack_boundary(env, regno, access_size, 1066 zero_size_allowed, meta); 1067 } 1068 } 1069 1070 static int check_func_arg(struct bpf_verifier_env *env, u32 regno, 1071 enum bpf_arg_type arg_type, 1072 struct bpf_call_arg_meta *meta) 1073 { 1074 struct bpf_reg_state *regs = env->cur_state.regs, *reg = ®s[regno]; 1075 enum bpf_reg_type expected_type, type = reg->type; 1076 int err = 0; 1077 1078 if (arg_type == ARG_DONTCARE) 1079 return 0; 1080 1081 if (type == NOT_INIT) { 1082 verbose("R%d !read_ok\n", regno); 1083 return -EACCES; 1084 } 1085 1086 if (arg_type == ARG_ANYTHING) { 1087 if (is_pointer_value(env, regno)) { 1088 verbose("R%d leaks addr into helper function\n", regno); 1089 return -EACCES; 1090 } 1091 return 0; 1092 } 1093 1094 if (type == PTR_TO_PACKET && 1095 !may_access_direct_pkt_data(env, meta, BPF_READ)) { 1096 verbose("helper access to the packet is not allowed\n"); 1097 return -EACCES; 1098 } 1099 1100 if (arg_type == ARG_PTR_TO_MAP_KEY || 1101 arg_type == ARG_PTR_TO_MAP_VALUE) { 1102 expected_type = PTR_TO_STACK; 1103 if (type != PTR_TO_PACKET && type != expected_type) 1104 goto err_type; 1105 } else if (arg_type == ARG_CONST_SIZE || 1106 arg_type == ARG_CONST_SIZE_OR_ZERO) { 1107 expected_type = CONST_IMM; 1108 /* One exception. Allow UNKNOWN_VALUE registers when the 1109 * boundaries are known and don't cause unsafe memory accesses 1110 */ 1111 if (type != UNKNOWN_VALUE && type != expected_type) 1112 goto err_type; 1113 } else if (arg_type == ARG_CONST_MAP_PTR) { 1114 expected_type = CONST_PTR_TO_MAP; 1115 if (type != expected_type) 1116 goto err_type; 1117 } else if (arg_type == ARG_PTR_TO_CTX) { 1118 expected_type = PTR_TO_CTX; 1119 if (type != expected_type) 1120 goto err_type; 1121 } else if (arg_type == ARG_PTR_TO_MEM || 1122 arg_type == ARG_PTR_TO_UNINIT_MEM) { 1123 expected_type = PTR_TO_STACK; 1124 /* One exception here. In case function allows for NULL to be 1125 * passed in as argument, it's a CONST_IMM type. Final test 1126 * happens during stack boundary checking. 1127 */ 1128 if (type == CONST_IMM && reg->imm == 0) 1129 /* final test in check_stack_boundary() */; 1130 else if (type != PTR_TO_PACKET && type != PTR_TO_MAP_VALUE && 1131 type != PTR_TO_MAP_VALUE_ADJ && type != expected_type) 1132 goto err_type; 1133 meta->raw_mode = arg_type == ARG_PTR_TO_UNINIT_MEM; 1134 } else { 1135 verbose("unsupported arg_type %d\n", arg_type); 1136 return -EFAULT; 1137 } 1138 1139 if (arg_type == ARG_CONST_MAP_PTR) { 1140 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */ 1141 meta->map_ptr = reg->map_ptr; 1142 } else if (arg_type == ARG_PTR_TO_MAP_KEY) { 1143 /* bpf_map_xxx(..., map_ptr, ..., key) call: 1144 * check that [key, key + map->key_size) are within 1145 * stack limits and initialized 1146 */ 1147 if (!meta->map_ptr) { 1148 /* in function declaration map_ptr must come before 1149 * map_key, so that it's verified and known before 1150 * we have to check map_key here. Otherwise it means 1151 * that kernel subsystem misconfigured verifier 1152 */ 1153 verbose("invalid map_ptr to access map->key\n"); 1154 return -EACCES; 1155 } 1156 if (type == PTR_TO_PACKET) 1157 err = check_packet_access(env, regno, 0, 1158 meta->map_ptr->key_size); 1159 else 1160 err = check_stack_boundary(env, regno, 1161 meta->map_ptr->key_size, 1162 false, NULL); 1163 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) { 1164 /* bpf_map_xxx(..., map_ptr, ..., value) call: 1165 * check [value, value + map->value_size) validity 1166 */ 1167 if (!meta->map_ptr) { 1168 /* kernel subsystem misconfigured verifier */ 1169 verbose("invalid map_ptr to access map->value\n"); 1170 return -EACCES; 1171 } 1172 if (type == PTR_TO_PACKET) 1173 err = check_packet_access(env, regno, 0, 1174 meta->map_ptr->value_size); 1175 else 1176 err = check_stack_boundary(env, regno, 1177 meta->map_ptr->value_size, 1178 false, NULL); 1179 } else if (arg_type == ARG_CONST_SIZE || 1180 arg_type == ARG_CONST_SIZE_OR_ZERO) { 1181 bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO); 1182 1183 /* bpf_xxx(..., buf, len) call will access 'len' bytes 1184 * from stack pointer 'buf'. Check it 1185 * note: regno == len, regno - 1 == buf 1186 */ 1187 if (regno == 0) { 1188 /* kernel subsystem misconfigured verifier */ 1189 verbose("ARG_CONST_SIZE cannot be first argument\n"); 1190 return -EACCES; 1191 } 1192 1193 /* If the register is UNKNOWN_VALUE, the access check happens 1194 * using its boundaries. Otherwise, just use its imm 1195 */ 1196 if (type == UNKNOWN_VALUE) { 1197 /* For unprivileged variable accesses, disable raw 1198 * mode so that the program is required to 1199 * initialize all the memory that the helper could 1200 * just partially fill up. 1201 */ 1202 meta = NULL; 1203 1204 if (reg->min_value < 0) { 1205 verbose("R%d min value is negative, either use unsigned or 'var &= const'\n", 1206 regno); 1207 return -EACCES; 1208 } 1209 1210 if (reg->min_value == 0) { 1211 err = check_helper_mem_access(env, regno - 1, 0, 1212 zero_size_allowed, 1213 meta); 1214 if (err) 1215 return err; 1216 } 1217 1218 if (reg->max_value == BPF_REGISTER_MAX_RANGE) { 1219 verbose("R%d unbounded memory access, use 'var &= const' or 'if (var < const)'\n", 1220 regno); 1221 return -EACCES; 1222 } 1223 err = check_helper_mem_access(env, regno - 1, 1224 reg->max_value, 1225 zero_size_allowed, meta); 1226 if (err) 1227 return err; 1228 } else { 1229 /* register is CONST_IMM */ 1230 err = check_helper_mem_access(env, regno - 1, reg->imm, 1231 zero_size_allowed, meta); 1232 } 1233 } 1234 1235 return err; 1236 err_type: 1237 verbose("R%d type=%s expected=%s\n", regno, 1238 reg_type_str[type], reg_type_str[expected_type]); 1239 return -EACCES; 1240 } 1241 1242 static int check_map_func_compatibility(struct bpf_map *map, int func_id) 1243 { 1244 if (!map) 1245 return 0; 1246 1247 /* We need a two way check, first is from map perspective ... */ 1248 switch (map->map_type) { 1249 case BPF_MAP_TYPE_PROG_ARRAY: 1250 if (func_id != BPF_FUNC_tail_call) 1251 goto error; 1252 break; 1253 case BPF_MAP_TYPE_PERF_EVENT_ARRAY: 1254 if (func_id != BPF_FUNC_perf_event_read && 1255 func_id != BPF_FUNC_perf_event_output) 1256 goto error; 1257 break; 1258 case BPF_MAP_TYPE_STACK_TRACE: 1259 if (func_id != BPF_FUNC_get_stackid) 1260 goto error; 1261 break; 1262 case BPF_MAP_TYPE_CGROUP_ARRAY: 1263 if (func_id != BPF_FUNC_skb_under_cgroup && 1264 func_id != BPF_FUNC_current_task_under_cgroup) 1265 goto error; 1266 break; 1267 case BPF_MAP_TYPE_ARRAY_OF_MAPS: 1268 case BPF_MAP_TYPE_HASH_OF_MAPS: 1269 if (func_id != BPF_FUNC_map_lookup_elem) 1270 goto error; 1271 default: 1272 break; 1273 } 1274 1275 /* ... and second from the function itself. */ 1276 switch (func_id) { 1277 case BPF_FUNC_tail_call: 1278 if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY) 1279 goto error; 1280 break; 1281 case BPF_FUNC_perf_event_read: 1282 case BPF_FUNC_perf_event_output: 1283 if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY) 1284 goto error; 1285 break; 1286 case BPF_FUNC_get_stackid: 1287 if (map->map_type != BPF_MAP_TYPE_STACK_TRACE) 1288 goto error; 1289 break; 1290 case BPF_FUNC_current_task_under_cgroup: 1291 case BPF_FUNC_skb_under_cgroup: 1292 if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY) 1293 goto error; 1294 break; 1295 default: 1296 break; 1297 } 1298 1299 return 0; 1300 error: 1301 verbose("cannot pass map_type %d into func %s#%d\n", 1302 map->map_type, func_id_name(func_id), func_id); 1303 return -EINVAL; 1304 } 1305 1306 static int check_raw_mode(const struct bpf_func_proto *fn) 1307 { 1308 int count = 0; 1309 1310 if (fn->arg1_type == ARG_PTR_TO_UNINIT_MEM) 1311 count++; 1312 if (fn->arg2_type == ARG_PTR_TO_UNINIT_MEM) 1313 count++; 1314 if (fn->arg3_type == ARG_PTR_TO_UNINIT_MEM) 1315 count++; 1316 if (fn->arg4_type == ARG_PTR_TO_UNINIT_MEM) 1317 count++; 1318 if (fn->arg5_type == ARG_PTR_TO_UNINIT_MEM) 1319 count++; 1320 1321 return count > 1 ? -EINVAL : 0; 1322 } 1323 1324 static void clear_all_pkt_pointers(struct bpf_verifier_env *env) 1325 { 1326 struct bpf_verifier_state *state = &env->cur_state; 1327 struct bpf_reg_state *regs = state->regs, *reg; 1328 int i; 1329 1330 for (i = 0; i < MAX_BPF_REG; i++) 1331 if (regs[i].type == PTR_TO_PACKET || 1332 regs[i].type == PTR_TO_PACKET_END) 1333 mark_reg_unknown_value(regs, i); 1334 1335 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 1336 if (state->stack_slot_type[i] != STACK_SPILL) 1337 continue; 1338 reg = &state->spilled_regs[i / BPF_REG_SIZE]; 1339 if (reg->type != PTR_TO_PACKET && 1340 reg->type != PTR_TO_PACKET_END) 1341 continue; 1342 reg->type = UNKNOWN_VALUE; 1343 reg->imm = 0; 1344 } 1345 } 1346 1347 static int check_call(struct bpf_verifier_env *env, int func_id, int insn_idx) 1348 { 1349 struct bpf_verifier_state *state = &env->cur_state; 1350 const struct bpf_func_proto *fn = NULL; 1351 struct bpf_reg_state *regs = state->regs; 1352 struct bpf_reg_state *reg; 1353 struct bpf_call_arg_meta meta; 1354 bool changes_data; 1355 int i, err; 1356 1357 /* find function prototype */ 1358 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) { 1359 verbose("invalid func %s#%d\n", func_id_name(func_id), func_id); 1360 return -EINVAL; 1361 } 1362 1363 if (env->prog->aux->ops->get_func_proto) 1364 fn = env->prog->aux->ops->get_func_proto(func_id); 1365 1366 if (!fn) { 1367 verbose("unknown func %s#%d\n", func_id_name(func_id), func_id); 1368 return -EINVAL; 1369 } 1370 1371 /* eBPF programs must be GPL compatible to use GPL-ed functions */ 1372 if (!env->prog->gpl_compatible && fn->gpl_only) { 1373 verbose("cannot call GPL only function from proprietary program\n"); 1374 return -EINVAL; 1375 } 1376 1377 changes_data = bpf_helper_changes_pkt_data(fn->func); 1378 1379 memset(&meta, 0, sizeof(meta)); 1380 meta.pkt_access = fn->pkt_access; 1381 1382 /* We only support one arg being in raw mode at the moment, which 1383 * is sufficient for the helper functions we have right now. 1384 */ 1385 err = check_raw_mode(fn); 1386 if (err) { 1387 verbose("kernel subsystem misconfigured func %s#%d\n", 1388 func_id_name(func_id), func_id); 1389 return err; 1390 } 1391 1392 /* check args */ 1393 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta); 1394 if (err) 1395 return err; 1396 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta); 1397 if (err) 1398 return err; 1399 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta); 1400 if (err) 1401 return err; 1402 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta); 1403 if (err) 1404 return err; 1405 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta); 1406 if (err) 1407 return err; 1408 1409 /* Mark slots with STACK_MISC in case of raw mode, stack offset 1410 * is inferred from register state. 1411 */ 1412 for (i = 0; i < meta.access_size; i++) { 1413 err = check_mem_access(env, meta.regno, i, BPF_B, BPF_WRITE, -1); 1414 if (err) 1415 return err; 1416 } 1417 1418 /* reset caller saved regs */ 1419 for (i = 0; i < CALLER_SAVED_REGS; i++) { 1420 reg = regs + caller_saved[i]; 1421 reg->type = NOT_INIT; 1422 reg->imm = 0; 1423 } 1424 1425 /* update return register */ 1426 if (fn->ret_type == RET_INTEGER) { 1427 regs[BPF_REG_0].type = UNKNOWN_VALUE; 1428 } else if (fn->ret_type == RET_VOID) { 1429 regs[BPF_REG_0].type = NOT_INIT; 1430 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) { 1431 struct bpf_insn_aux_data *insn_aux; 1432 1433 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL; 1434 regs[BPF_REG_0].max_value = regs[BPF_REG_0].min_value = 0; 1435 /* remember map_ptr, so that check_map_access() 1436 * can check 'value_size' boundary of memory access 1437 * to map element returned from bpf_map_lookup_elem() 1438 */ 1439 if (meta.map_ptr == NULL) { 1440 verbose("kernel subsystem misconfigured verifier\n"); 1441 return -EINVAL; 1442 } 1443 regs[BPF_REG_0].map_ptr = meta.map_ptr; 1444 regs[BPF_REG_0].id = ++env->id_gen; 1445 insn_aux = &env->insn_aux_data[insn_idx]; 1446 if (!insn_aux->map_ptr) 1447 insn_aux->map_ptr = meta.map_ptr; 1448 else if (insn_aux->map_ptr != meta.map_ptr) 1449 insn_aux->map_ptr = BPF_MAP_PTR_POISON; 1450 } else { 1451 verbose("unknown return type %d of func %s#%d\n", 1452 fn->ret_type, func_id_name(func_id), func_id); 1453 return -EINVAL; 1454 } 1455 1456 err = check_map_func_compatibility(meta.map_ptr, func_id); 1457 if (err) 1458 return err; 1459 1460 if (changes_data) 1461 clear_all_pkt_pointers(env); 1462 return 0; 1463 } 1464 1465 static int check_packet_ptr_add(struct bpf_verifier_env *env, 1466 struct bpf_insn *insn) 1467 { 1468 struct bpf_reg_state *regs = env->cur_state.regs; 1469 struct bpf_reg_state *dst_reg = ®s[insn->dst_reg]; 1470 struct bpf_reg_state *src_reg = ®s[insn->src_reg]; 1471 struct bpf_reg_state tmp_reg; 1472 s32 imm; 1473 1474 if (BPF_SRC(insn->code) == BPF_K) { 1475 /* pkt_ptr += imm */ 1476 imm = insn->imm; 1477 1478 add_imm: 1479 if (imm < 0) { 1480 verbose("addition of negative constant to packet pointer is not allowed\n"); 1481 return -EACCES; 1482 } 1483 if (imm >= MAX_PACKET_OFF || 1484 imm + dst_reg->off >= MAX_PACKET_OFF) { 1485 verbose("constant %d is too large to add to packet pointer\n", 1486 imm); 1487 return -EACCES; 1488 } 1489 /* a constant was added to pkt_ptr. 1490 * Remember it while keeping the same 'id' 1491 */ 1492 dst_reg->off += imm; 1493 } else { 1494 bool had_id; 1495 1496 if (src_reg->type == PTR_TO_PACKET) { 1497 /* R6=pkt(id=0,off=0,r=62) R7=imm22; r7 += r6 */ 1498 tmp_reg = *dst_reg; /* save r7 state */ 1499 *dst_reg = *src_reg; /* copy pkt_ptr state r6 into r7 */ 1500 src_reg = &tmp_reg; /* pretend it's src_reg state */ 1501 /* if the checks below reject it, the copy won't matter, 1502 * since we're rejecting the whole program. If all ok, 1503 * then imm22 state will be added to r7 1504 * and r7 will be pkt(id=0,off=22,r=62) while 1505 * r6 will stay as pkt(id=0,off=0,r=62) 1506 */ 1507 } 1508 1509 if (src_reg->type == CONST_IMM) { 1510 /* pkt_ptr += reg where reg is known constant */ 1511 imm = src_reg->imm; 1512 goto add_imm; 1513 } 1514 /* disallow pkt_ptr += reg 1515 * if reg is not uknown_value with guaranteed zero upper bits 1516 * otherwise pkt_ptr may overflow and addition will become 1517 * subtraction which is not allowed 1518 */ 1519 if (src_reg->type != UNKNOWN_VALUE) { 1520 verbose("cannot add '%s' to ptr_to_packet\n", 1521 reg_type_str[src_reg->type]); 1522 return -EACCES; 1523 } 1524 if (src_reg->imm < 48) { 1525 verbose("cannot add integer value with %lld upper zero bits to ptr_to_packet\n", 1526 src_reg->imm); 1527 return -EACCES; 1528 } 1529 1530 had_id = (dst_reg->id != 0); 1531 1532 /* dst_reg stays as pkt_ptr type and since some positive 1533 * integer value was added to the pointer, increment its 'id' 1534 */ 1535 dst_reg->id = ++env->id_gen; 1536 1537 /* something was added to pkt_ptr, set range to zero */ 1538 dst_reg->aux_off += dst_reg->off; 1539 dst_reg->off = 0; 1540 dst_reg->range = 0; 1541 if (had_id) 1542 dst_reg->aux_off_align = min(dst_reg->aux_off_align, 1543 src_reg->min_align); 1544 else 1545 dst_reg->aux_off_align = src_reg->min_align; 1546 } 1547 return 0; 1548 } 1549 1550 static int evaluate_reg_alu(struct bpf_verifier_env *env, struct bpf_insn *insn) 1551 { 1552 struct bpf_reg_state *regs = env->cur_state.regs; 1553 struct bpf_reg_state *dst_reg = ®s[insn->dst_reg]; 1554 u8 opcode = BPF_OP(insn->code); 1555 s64 imm_log2; 1556 1557 /* for type == UNKNOWN_VALUE: 1558 * imm > 0 -> number of zero upper bits 1559 * imm == 0 -> don't track which is the same as all bits can be non-zero 1560 */ 1561 1562 if (BPF_SRC(insn->code) == BPF_X) { 1563 struct bpf_reg_state *src_reg = ®s[insn->src_reg]; 1564 1565 if (src_reg->type == UNKNOWN_VALUE && src_reg->imm > 0 && 1566 dst_reg->imm && opcode == BPF_ADD) { 1567 /* dreg += sreg 1568 * where both have zero upper bits. Adding them 1569 * can only result making one more bit non-zero 1570 * in the larger value. 1571 * Ex. 0xffff (imm=48) + 1 (imm=63) = 0x10000 (imm=47) 1572 * 0xffff (imm=48) + 0xffff = 0x1fffe (imm=47) 1573 */ 1574 dst_reg->imm = min(dst_reg->imm, src_reg->imm); 1575 dst_reg->imm--; 1576 return 0; 1577 } 1578 if (src_reg->type == CONST_IMM && src_reg->imm > 0 && 1579 dst_reg->imm && opcode == BPF_ADD) { 1580 /* dreg += sreg 1581 * where dreg has zero upper bits and sreg is const. 1582 * Adding them can only result making one more bit 1583 * non-zero in the larger value. 1584 */ 1585 imm_log2 = __ilog2_u64((long long)src_reg->imm); 1586 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2); 1587 dst_reg->imm--; 1588 return 0; 1589 } 1590 /* all other cases non supported yet, just mark dst_reg */ 1591 dst_reg->imm = 0; 1592 return 0; 1593 } 1594 1595 /* sign extend 32-bit imm into 64-bit to make sure that 1596 * negative values occupy bit 63. Note ilog2() would have 1597 * been incorrect, since sizeof(insn->imm) == 4 1598 */ 1599 imm_log2 = __ilog2_u64((long long)insn->imm); 1600 1601 if (dst_reg->imm && opcode == BPF_LSH) { 1602 /* reg <<= imm 1603 * if reg was a result of 2 byte load, then its imm == 48 1604 * which means that upper 48 bits are zero and shifting this reg 1605 * left by 4 would mean that upper 44 bits are still zero 1606 */ 1607 dst_reg->imm -= insn->imm; 1608 } else if (dst_reg->imm && opcode == BPF_MUL) { 1609 /* reg *= imm 1610 * if multiplying by 14 subtract 4 1611 * This is conservative calculation of upper zero bits. 1612 * It's not trying to special case insn->imm == 1 or 0 cases 1613 */ 1614 dst_reg->imm -= imm_log2 + 1; 1615 } else if (opcode == BPF_AND) { 1616 /* reg &= imm */ 1617 dst_reg->imm = 63 - imm_log2; 1618 } else if (dst_reg->imm && opcode == BPF_ADD) { 1619 /* reg += imm */ 1620 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2); 1621 dst_reg->imm--; 1622 } else if (opcode == BPF_RSH) { 1623 /* reg >>= imm 1624 * which means that after right shift, upper bits will be zero 1625 * note that verifier already checked that 1626 * 0 <= imm < 64 for shift insn 1627 */ 1628 dst_reg->imm += insn->imm; 1629 if (unlikely(dst_reg->imm > 64)) 1630 /* some dumb code did: 1631 * r2 = *(u32 *)mem; 1632 * r2 >>= 32; 1633 * and all bits are zero now */ 1634 dst_reg->imm = 64; 1635 } else { 1636 /* all other alu ops, means that we don't know what will 1637 * happen to the value, mark it with unknown number of zero bits 1638 */ 1639 dst_reg->imm = 0; 1640 } 1641 1642 if (dst_reg->imm < 0) { 1643 /* all 64 bits of the register can contain non-zero bits 1644 * and such value cannot be added to ptr_to_packet, since it 1645 * may overflow, mark it as unknown to avoid further eval 1646 */ 1647 dst_reg->imm = 0; 1648 } 1649 return 0; 1650 } 1651 1652 static int evaluate_reg_imm_alu(struct bpf_verifier_env *env, 1653 struct bpf_insn *insn) 1654 { 1655 struct bpf_reg_state *regs = env->cur_state.regs; 1656 struct bpf_reg_state *dst_reg = ®s[insn->dst_reg]; 1657 struct bpf_reg_state *src_reg = ®s[insn->src_reg]; 1658 u8 opcode = BPF_OP(insn->code); 1659 u64 dst_imm = dst_reg->imm; 1660 1661 /* dst_reg->type == CONST_IMM here. Simulate execution of insns 1662 * containing ALU ops. Don't care about overflow or negative 1663 * values, just add/sub/... them; registers are in u64. 1664 */ 1665 if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_K) { 1666 dst_imm += insn->imm; 1667 } else if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_X && 1668 src_reg->type == CONST_IMM) { 1669 dst_imm += src_reg->imm; 1670 } else if (opcode == BPF_SUB && BPF_SRC(insn->code) == BPF_K) { 1671 dst_imm -= insn->imm; 1672 } else if (opcode == BPF_SUB && BPF_SRC(insn->code) == BPF_X && 1673 src_reg->type == CONST_IMM) { 1674 dst_imm -= src_reg->imm; 1675 } else if (opcode == BPF_MUL && BPF_SRC(insn->code) == BPF_K) { 1676 dst_imm *= insn->imm; 1677 } else if (opcode == BPF_MUL && BPF_SRC(insn->code) == BPF_X && 1678 src_reg->type == CONST_IMM) { 1679 dst_imm *= src_reg->imm; 1680 } else if (opcode == BPF_OR && BPF_SRC(insn->code) == BPF_K) { 1681 dst_imm |= insn->imm; 1682 } else if (opcode == BPF_OR && BPF_SRC(insn->code) == BPF_X && 1683 src_reg->type == CONST_IMM) { 1684 dst_imm |= src_reg->imm; 1685 } else if (opcode == BPF_AND && BPF_SRC(insn->code) == BPF_K) { 1686 dst_imm &= insn->imm; 1687 } else if (opcode == BPF_AND && BPF_SRC(insn->code) == BPF_X && 1688 src_reg->type == CONST_IMM) { 1689 dst_imm &= src_reg->imm; 1690 } else if (opcode == BPF_RSH && BPF_SRC(insn->code) == BPF_K) { 1691 dst_imm >>= insn->imm; 1692 } else if (opcode == BPF_RSH && BPF_SRC(insn->code) == BPF_X && 1693 src_reg->type == CONST_IMM) { 1694 dst_imm >>= src_reg->imm; 1695 } else if (opcode == BPF_LSH && BPF_SRC(insn->code) == BPF_K) { 1696 dst_imm <<= insn->imm; 1697 } else if (opcode == BPF_LSH && BPF_SRC(insn->code) == BPF_X && 1698 src_reg->type == CONST_IMM) { 1699 dst_imm <<= src_reg->imm; 1700 } else { 1701 mark_reg_unknown_value(regs, insn->dst_reg); 1702 goto out; 1703 } 1704 1705 dst_reg->imm = dst_imm; 1706 out: 1707 return 0; 1708 } 1709 1710 static void check_reg_overflow(struct bpf_reg_state *reg) 1711 { 1712 if (reg->max_value > BPF_REGISTER_MAX_RANGE) 1713 reg->max_value = BPF_REGISTER_MAX_RANGE; 1714 if (reg->min_value < BPF_REGISTER_MIN_RANGE || 1715 reg->min_value > BPF_REGISTER_MAX_RANGE) 1716 reg->min_value = BPF_REGISTER_MIN_RANGE; 1717 } 1718 1719 static u32 calc_align(u32 imm) 1720 { 1721 if (!imm) 1722 return 1U << 31; 1723 return imm - ((imm - 1) & imm); 1724 } 1725 1726 static void adjust_reg_min_max_vals(struct bpf_verifier_env *env, 1727 struct bpf_insn *insn) 1728 { 1729 struct bpf_reg_state *regs = env->cur_state.regs, *dst_reg; 1730 s64 min_val = BPF_REGISTER_MIN_RANGE; 1731 u64 max_val = BPF_REGISTER_MAX_RANGE; 1732 u8 opcode = BPF_OP(insn->code); 1733 u32 dst_align, src_align; 1734 1735 dst_reg = ®s[insn->dst_reg]; 1736 src_align = 0; 1737 if (BPF_SRC(insn->code) == BPF_X) { 1738 check_reg_overflow(®s[insn->src_reg]); 1739 min_val = regs[insn->src_reg].min_value; 1740 max_val = regs[insn->src_reg].max_value; 1741 1742 /* If the source register is a random pointer then the 1743 * min_value/max_value values represent the range of the known 1744 * accesses into that value, not the actual min/max value of the 1745 * register itself. In this case we have to reset the reg range 1746 * values so we know it is not safe to look at. 1747 */ 1748 if (regs[insn->src_reg].type != CONST_IMM && 1749 regs[insn->src_reg].type != UNKNOWN_VALUE) { 1750 min_val = BPF_REGISTER_MIN_RANGE; 1751 max_val = BPF_REGISTER_MAX_RANGE; 1752 src_align = 0; 1753 } else { 1754 src_align = regs[insn->src_reg].min_align; 1755 } 1756 } else if (insn->imm < BPF_REGISTER_MAX_RANGE && 1757 (s64)insn->imm > BPF_REGISTER_MIN_RANGE) { 1758 min_val = max_val = insn->imm; 1759 src_align = calc_align(insn->imm); 1760 } 1761 1762 dst_align = dst_reg->min_align; 1763 1764 /* We don't know anything about what was done to this register, mark it 1765 * as unknown. 1766 */ 1767 if (min_val == BPF_REGISTER_MIN_RANGE && 1768 max_val == BPF_REGISTER_MAX_RANGE) { 1769 reset_reg_range_values(regs, insn->dst_reg); 1770 return; 1771 } 1772 1773 /* If one of our values was at the end of our ranges then we can't just 1774 * do our normal operations to the register, we need to set the values 1775 * to the min/max since they are undefined. 1776 */ 1777 if (min_val == BPF_REGISTER_MIN_RANGE) 1778 dst_reg->min_value = BPF_REGISTER_MIN_RANGE; 1779 if (max_val == BPF_REGISTER_MAX_RANGE) 1780 dst_reg->max_value = BPF_REGISTER_MAX_RANGE; 1781 1782 switch (opcode) { 1783 case BPF_ADD: 1784 if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) 1785 dst_reg->min_value += min_val; 1786 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1787 dst_reg->max_value += max_val; 1788 dst_reg->min_align = min(src_align, dst_align); 1789 break; 1790 case BPF_SUB: 1791 if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) 1792 dst_reg->min_value -= min_val; 1793 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1794 dst_reg->max_value -= max_val; 1795 dst_reg->min_align = min(src_align, dst_align); 1796 break; 1797 case BPF_MUL: 1798 if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) 1799 dst_reg->min_value *= min_val; 1800 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1801 dst_reg->max_value *= max_val; 1802 dst_reg->min_align = max(src_align, dst_align); 1803 break; 1804 case BPF_AND: 1805 /* Disallow AND'ing of negative numbers, ain't nobody got time 1806 * for that. Otherwise the minimum is 0 and the max is the max 1807 * value we could AND against. 1808 */ 1809 if (min_val < 0) 1810 dst_reg->min_value = BPF_REGISTER_MIN_RANGE; 1811 else 1812 dst_reg->min_value = 0; 1813 dst_reg->max_value = max_val; 1814 dst_reg->min_align = max(src_align, dst_align); 1815 break; 1816 case BPF_LSH: 1817 /* Gotta have special overflow logic here, if we're shifting 1818 * more than MAX_RANGE then just assume we have an invalid 1819 * range. 1820 */ 1821 if (min_val > ilog2(BPF_REGISTER_MAX_RANGE)) { 1822 dst_reg->min_value = BPF_REGISTER_MIN_RANGE; 1823 dst_reg->min_align = 1; 1824 } else { 1825 if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) 1826 dst_reg->min_value <<= min_val; 1827 if (!dst_reg->min_align) 1828 dst_reg->min_align = 1; 1829 dst_reg->min_align <<= min_val; 1830 } 1831 if (max_val > ilog2(BPF_REGISTER_MAX_RANGE)) 1832 dst_reg->max_value = BPF_REGISTER_MAX_RANGE; 1833 else if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1834 dst_reg->max_value <<= max_val; 1835 break; 1836 case BPF_RSH: 1837 /* RSH by a negative number is undefined, and the BPF_RSH is an 1838 * unsigned shift, so make the appropriate casts. 1839 */ 1840 if (min_val < 0 || dst_reg->min_value < 0) { 1841 dst_reg->min_value = BPF_REGISTER_MIN_RANGE; 1842 } else { 1843 dst_reg->min_value = 1844 (u64)(dst_reg->min_value) >> min_val; 1845 } 1846 if (min_val < 0) { 1847 dst_reg->min_align = 1; 1848 } else { 1849 dst_reg->min_align >>= (u64) min_val; 1850 if (!dst_reg->min_align) 1851 dst_reg->min_align = 1; 1852 } 1853 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1854 dst_reg->max_value >>= max_val; 1855 break; 1856 default: 1857 reset_reg_range_values(regs, insn->dst_reg); 1858 break; 1859 } 1860 1861 check_reg_overflow(dst_reg); 1862 } 1863 1864 /* check validity of 32-bit and 64-bit arithmetic operations */ 1865 static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn) 1866 { 1867 struct bpf_reg_state *regs = env->cur_state.regs, *dst_reg; 1868 u8 opcode = BPF_OP(insn->code); 1869 int err; 1870 1871 if (opcode == BPF_END || opcode == BPF_NEG) { 1872 if (opcode == BPF_NEG) { 1873 if (BPF_SRC(insn->code) != 0 || 1874 insn->src_reg != BPF_REG_0 || 1875 insn->off != 0 || insn->imm != 0) { 1876 verbose("BPF_NEG uses reserved fields\n"); 1877 return -EINVAL; 1878 } 1879 } else { 1880 if (insn->src_reg != BPF_REG_0 || insn->off != 0 || 1881 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) { 1882 verbose("BPF_END uses reserved fields\n"); 1883 return -EINVAL; 1884 } 1885 } 1886 1887 /* check src operand */ 1888 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1889 if (err) 1890 return err; 1891 1892 if (is_pointer_value(env, insn->dst_reg)) { 1893 verbose("R%d pointer arithmetic prohibited\n", 1894 insn->dst_reg); 1895 return -EACCES; 1896 } 1897 1898 /* check dest operand */ 1899 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1900 if (err) 1901 return err; 1902 1903 } else if (opcode == BPF_MOV) { 1904 1905 if (BPF_SRC(insn->code) == BPF_X) { 1906 if (insn->imm != 0 || insn->off != 0) { 1907 verbose("BPF_MOV uses reserved fields\n"); 1908 return -EINVAL; 1909 } 1910 1911 /* check src operand */ 1912 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1913 if (err) 1914 return err; 1915 } else { 1916 if (insn->src_reg != BPF_REG_0 || insn->off != 0) { 1917 verbose("BPF_MOV uses reserved fields\n"); 1918 return -EINVAL; 1919 } 1920 } 1921 1922 /* check dest operand */ 1923 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1924 if (err) 1925 return err; 1926 1927 /* we are setting our register to something new, we need to 1928 * reset its range values. 1929 */ 1930 reset_reg_range_values(regs, insn->dst_reg); 1931 1932 if (BPF_SRC(insn->code) == BPF_X) { 1933 if (BPF_CLASS(insn->code) == BPF_ALU64) { 1934 /* case: R1 = R2 1935 * copy register state to dest reg 1936 */ 1937 regs[insn->dst_reg] = regs[insn->src_reg]; 1938 } else { 1939 if (is_pointer_value(env, insn->src_reg)) { 1940 verbose("R%d partial copy of pointer\n", 1941 insn->src_reg); 1942 return -EACCES; 1943 } 1944 mark_reg_unknown_value(regs, insn->dst_reg); 1945 } 1946 } else { 1947 /* case: R = imm 1948 * remember the value we stored into this reg 1949 */ 1950 regs[insn->dst_reg].type = CONST_IMM; 1951 regs[insn->dst_reg].imm = insn->imm; 1952 regs[insn->dst_reg].max_value = insn->imm; 1953 regs[insn->dst_reg].min_value = insn->imm; 1954 regs[insn->dst_reg].min_align = calc_align(insn->imm); 1955 } 1956 1957 } else if (opcode > BPF_END) { 1958 verbose("invalid BPF_ALU opcode %x\n", opcode); 1959 return -EINVAL; 1960 1961 } else { /* all other ALU ops: and, sub, xor, add, ... */ 1962 1963 if (BPF_SRC(insn->code) == BPF_X) { 1964 if (insn->imm != 0 || insn->off != 0) { 1965 verbose("BPF_ALU uses reserved fields\n"); 1966 return -EINVAL; 1967 } 1968 /* check src1 operand */ 1969 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1970 if (err) 1971 return err; 1972 } else { 1973 if (insn->src_reg != BPF_REG_0 || insn->off != 0) { 1974 verbose("BPF_ALU uses reserved fields\n"); 1975 return -EINVAL; 1976 } 1977 } 1978 1979 /* check src2 operand */ 1980 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1981 if (err) 1982 return err; 1983 1984 if ((opcode == BPF_MOD || opcode == BPF_DIV) && 1985 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) { 1986 verbose("div by zero\n"); 1987 return -EINVAL; 1988 } 1989 1990 if ((opcode == BPF_LSH || opcode == BPF_RSH || 1991 opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) { 1992 int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32; 1993 1994 if (insn->imm < 0 || insn->imm >= size) { 1995 verbose("invalid shift %d\n", insn->imm); 1996 return -EINVAL; 1997 } 1998 } 1999 2000 /* check dest operand */ 2001 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); 2002 if (err) 2003 return err; 2004 2005 dst_reg = ®s[insn->dst_reg]; 2006 2007 /* first we want to adjust our ranges. */ 2008 adjust_reg_min_max_vals(env, insn); 2009 2010 /* pattern match 'bpf_add Rx, imm' instruction */ 2011 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 && 2012 dst_reg->type == FRAME_PTR && BPF_SRC(insn->code) == BPF_K) { 2013 dst_reg->type = PTR_TO_STACK; 2014 dst_reg->imm = insn->imm; 2015 return 0; 2016 } else if (opcode == BPF_ADD && 2017 BPF_CLASS(insn->code) == BPF_ALU64 && 2018 dst_reg->type == PTR_TO_STACK && 2019 ((BPF_SRC(insn->code) == BPF_X && 2020 regs[insn->src_reg].type == CONST_IMM) || 2021 BPF_SRC(insn->code) == BPF_K)) { 2022 if (BPF_SRC(insn->code) == BPF_X) 2023 dst_reg->imm += regs[insn->src_reg].imm; 2024 else 2025 dst_reg->imm += insn->imm; 2026 return 0; 2027 } else if (opcode == BPF_ADD && 2028 BPF_CLASS(insn->code) == BPF_ALU64 && 2029 (dst_reg->type == PTR_TO_PACKET || 2030 (BPF_SRC(insn->code) == BPF_X && 2031 regs[insn->src_reg].type == PTR_TO_PACKET))) { 2032 /* ptr_to_packet += K|X */ 2033 return check_packet_ptr_add(env, insn); 2034 } else if (BPF_CLASS(insn->code) == BPF_ALU64 && 2035 dst_reg->type == UNKNOWN_VALUE && 2036 env->allow_ptr_leaks) { 2037 /* unknown += K|X */ 2038 return evaluate_reg_alu(env, insn); 2039 } else if (BPF_CLASS(insn->code) == BPF_ALU64 && 2040 dst_reg->type == CONST_IMM && 2041 env->allow_ptr_leaks) { 2042 /* reg_imm += K|X */ 2043 return evaluate_reg_imm_alu(env, insn); 2044 } else if (is_pointer_value(env, insn->dst_reg)) { 2045 verbose("R%d pointer arithmetic prohibited\n", 2046 insn->dst_reg); 2047 return -EACCES; 2048 } else if (BPF_SRC(insn->code) == BPF_X && 2049 is_pointer_value(env, insn->src_reg)) { 2050 verbose("R%d pointer arithmetic prohibited\n", 2051 insn->src_reg); 2052 return -EACCES; 2053 } 2054 2055 /* If we did pointer math on a map value then just set it to our 2056 * PTR_TO_MAP_VALUE_ADJ type so we can deal with any stores or 2057 * loads to this register appropriately, otherwise just mark the 2058 * register as unknown. 2059 */ 2060 if (env->allow_ptr_leaks && 2061 BPF_CLASS(insn->code) == BPF_ALU64 && opcode == BPF_ADD && 2062 (dst_reg->type == PTR_TO_MAP_VALUE || 2063 dst_reg->type == PTR_TO_MAP_VALUE_ADJ)) 2064 dst_reg->type = PTR_TO_MAP_VALUE_ADJ; 2065 else 2066 mark_reg_unknown_value(regs, insn->dst_reg); 2067 } 2068 2069 return 0; 2070 } 2071 2072 static void find_good_pkt_pointers(struct bpf_verifier_state *state, 2073 struct bpf_reg_state *dst_reg) 2074 { 2075 struct bpf_reg_state *regs = state->regs, *reg; 2076 int i; 2077 2078 /* LLVM can generate two kind of checks: 2079 * 2080 * Type 1: 2081 * 2082 * r2 = r3; 2083 * r2 += 8; 2084 * if (r2 > pkt_end) goto <handle exception> 2085 * <access okay> 2086 * 2087 * Where: 2088 * r2 == dst_reg, pkt_end == src_reg 2089 * r2=pkt(id=n,off=8,r=0) 2090 * r3=pkt(id=n,off=0,r=0) 2091 * 2092 * Type 2: 2093 * 2094 * r2 = r3; 2095 * r2 += 8; 2096 * if (pkt_end >= r2) goto <access okay> 2097 * <handle exception> 2098 * 2099 * Where: 2100 * pkt_end == dst_reg, r2 == src_reg 2101 * r2=pkt(id=n,off=8,r=0) 2102 * r3=pkt(id=n,off=0,r=0) 2103 * 2104 * Find register r3 and mark its range as r3=pkt(id=n,off=0,r=8) 2105 * so that range of bytes [r3, r3 + 8) is safe to access. 2106 */ 2107 2108 for (i = 0; i < MAX_BPF_REG; i++) 2109 if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id) 2110 /* keep the maximum range already checked */ 2111 regs[i].range = max(regs[i].range, dst_reg->off); 2112 2113 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 2114 if (state->stack_slot_type[i] != STACK_SPILL) 2115 continue; 2116 reg = &state->spilled_regs[i / BPF_REG_SIZE]; 2117 if (reg->type == PTR_TO_PACKET && reg->id == dst_reg->id) 2118 reg->range = max(reg->range, dst_reg->off); 2119 } 2120 } 2121 2122 /* Adjusts the register min/max values in the case that the dst_reg is the 2123 * variable register that we are working on, and src_reg is a constant or we're 2124 * simply doing a BPF_K check. 2125 */ 2126 static void reg_set_min_max(struct bpf_reg_state *true_reg, 2127 struct bpf_reg_state *false_reg, u64 val, 2128 u8 opcode) 2129 { 2130 switch (opcode) { 2131 case BPF_JEQ: 2132 /* If this is false then we know nothing Jon Snow, but if it is 2133 * true then we know for sure. 2134 */ 2135 true_reg->max_value = true_reg->min_value = val; 2136 break; 2137 case BPF_JNE: 2138 /* If this is true we know nothing Jon Snow, but if it is false 2139 * we know the value for sure; 2140 */ 2141 false_reg->max_value = false_reg->min_value = val; 2142 break; 2143 case BPF_JGT: 2144 /* Unsigned comparison, the minimum value is 0. */ 2145 false_reg->min_value = 0; 2146 /* fallthrough */ 2147 case BPF_JSGT: 2148 /* If this is false then we know the maximum val is val, 2149 * otherwise we know the min val is val+1. 2150 */ 2151 false_reg->max_value = val; 2152 true_reg->min_value = val + 1; 2153 break; 2154 case BPF_JGE: 2155 /* Unsigned comparison, the minimum value is 0. */ 2156 false_reg->min_value = 0; 2157 /* fallthrough */ 2158 case BPF_JSGE: 2159 /* If this is false then we know the maximum value is val - 1, 2160 * otherwise we know the mimimum value is val. 2161 */ 2162 false_reg->max_value = val - 1; 2163 true_reg->min_value = val; 2164 break; 2165 default: 2166 break; 2167 } 2168 2169 check_reg_overflow(false_reg); 2170 check_reg_overflow(true_reg); 2171 } 2172 2173 /* Same as above, but for the case that dst_reg is a CONST_IMM reg and src_reg 2174 * is the variable reg. 2175 */ 2176 static void reg_set_min_max_inv(struct bpf_reg_state *true_reg, 2177 struct bpf_reg_state *false_reg, u64 val, 2178 u8 opcode) 2179 { 2180 switch (opcode) { 2181 case BPF_JEQ: 2182 /* If this is false then we know nothing Jon Snow, but if it is 2183 * true then we know for sure. 2184 */ 2185 true_reg->max_value = true_reg->min_value = val; 2186 break; 2187 case BPF_JNE: 2188 /* If this is true we know nothing Jon Snow, but if it is false 2189 * we know the value for sure; 2190 */ 2191 false_reg->max_value = false_reg->min_value = val; 2192 break; 2193 case BPF_JGT: 2194 /* Unsigned comparison, the minimum value is 0. */ 2195 true_reg->min_value = 0; 2196 /* fallthrough */ 2197 case BPF_JSGT: 2198 /* 2199 * If this is false, then the val is <= the register, if it is 2200 * true the register <= to the val. 2201 */ 2202 false_reg->min_value = val; 2203 true_reg->max_value = val - 1; 2204 break; 2205 case BPF_JGE: 2206 /* Unsigned comparison, the minimum value is 0. */ 2207 true_reg->min_value = 0; 2208 /* fallthrough */ 2209 case BPF_JSGE: 2210 /* If this is false then constant < register, if it is true then 2211 * the register < constant. 2212 */ 2213 false_reg->min_value = val + 1; 2214 true_reg->max_value = val; 2215 break; 2216 default: 2217 break; 2218 } 2219 2220 check_reg_overflow(false_reg); 2221 check_reg_overflow(true_reg); 2222 } 2223 2224 static void mark_map_reg(struct bpf_reg_state *regs, u32 regno, u32 id, 2225 enum bpf_reg_type type) 2226 { 2227 struct bpf_reg_state *reg = ®s[regno]; 2228 2229 if (reg->type == PTR_TO_MAP_VALUE_OR_NULL && reg->id == id) { 2230 if (type == UNKNOWN_VALUE) { 2231 __mark_reg_unknown_value(regs, regno); 2232 } else if (reg->map_ptr->inner_map_meta) { 2233 reg->type = CONST_PTR_TO_MAP; 2234 reg->map_ptr = reg->map_ptr->inner_map_meta; 2235 } else { 2236 reg->type = type; 2237 } 2238 /* We don't need id from this point onwards anymore, thus we 2239 * should better reset it, so that state pruning has chances 2240 * to take effect. 2241 */ 2242 reg->id = 0; 2243 } 2244 } 2245 2246 /* The logic is similar to find_good_pkt_pointers(), both could eventually 2247 * be folded together at some point. 2248 */ 2249 static void mark_map_regs(struct bpf_verifier_state *state, u32 regno, 2250 enum bpf_reg_type type) 2251 { 2252 struct bpf_reg_state *regs = state->regs; 2253 u32 id = regs[regno].id; 2254 int i; 2255 2256 for (i = 0; i < MAX_BPF_REG; i++) 2257 mark_map_reg(regs, i, id, type); 2258 2259 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 2260 if (state->stack_slot_type[i] != STACK_SPILL) 2261 continue; 2262 mark_map_reg(state->spilled_regs, i / BPF_REG_SIZE, id, type); 2263 } 2264 } 2265 2266 static int check_cond_jmp_op(struct bpf_verifier_env *env, 2267 struct bpf_insn *insn, int *insn_idx) 2268 { 2269 struct bpf_verifier_state *other_branch, *this_branch = &env->cur_state; 2270 struct bpf_reg_state *regs = this_branch->regs, *dst_reg; 2271 u8 opcode = BPF_OP(insn->code); 2272 int err; 2273 2274 if (opcode > BPF_EXIT) { 2275 verbose("invalid BPF_JMP opcode %x\n", opcode); 2276 return -EINVAL; 2277 } 2278 2279 if (BPF_SRC(insn->code) == BPF_X) { 2280 if (insn->imm != 0) { 2281 verbose("BPF_JMP uses reserved fields\n"); 2282 return -EINVAL; 2283 } 2284 2285 /* check src1 operand */ 2286 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2287 if (err) 2288 return err; 2289 2290 if (is_pointer_value(env, insn->src_reg)) { 2291 verbose("R%d pointer comparison prohibited\n", 2292 insn->src_reg); 2293 return -EACCES; 2294 } 2295 } else { 2296 if (insn->src_reg != BPF_REG_0) { 2297 verbose("BPF_JMP uses reserved fields\n"); 2298 return -EINVAL; 2299 } 2300 } 2301 2302 /* check src2 operand */ 2303 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 2304 if (err) 2305 return err; 2306 2307 dst_reg = ®s[insn->dst_reg]; 2308 2309 /* detect if R == 0 where R was initialized to zero earlier */ 2310 if (BPF_SRC(insn->code) == BPF_K && 2311 (opcode == BPF_JEQ || opcode == BPF_JNE) && 2312 dst_reg->type == CONST_IMM && dst_reg->imm == insn->imm) { 2313 if (opcode == BPF_JEQ) { 2314 /* if (imm == imm) goto pc+off; 2315 * only follow the goto, ignore fall-through 2316 */ 2317 *insn_idx += insn->off; 2318 return 0; 2319 } else { 2320 /* if (imm != imm) goto pc+off; 2321 * only follow fall-through branch, since 2322 * that's where the program will go 2323 */ 2324 return 0; 2325 } 2326 } 2327 2328 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx); 2329 if (!other_branch) 2330 return -EFAULT; 2331 2332 /* detect if we are comparing against a constant value so we can adjust 2333 * our min/max values for our dst register. 2334 */ 2335 if (BPF_SRC(insn->code) == BPF_X) { 2336 if (regs[insn->src_reg].type == CONST_IMM) 2337 reg_set_min_max(&other_branch->regs[insn->dst_reg], 2338 dst_reg, regs[insn->src_reg].imm, 2339 opcode); 2340 else if (dst_reg->type == CONST_IMM) 2341 reg_set_min_max_inv(&other_branch->regs[insn->src_reg], 2342 ®s[insn->src_reg], dst_reg->imm, 2343 opcode); 2344 } else { 2345 reg_set_min_max(&other_branch->regs[insn->dst_reg], 2346 dst_reg, insn->imm, opcode); 2347 } 2348 2349 /* detect if R == 0 where R is returned from bpf_map_lookup_elem() */ 2350 if (BPF_SRC(insn->code) == BPF_K && 2351 insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) && 2352 dst_reg->type == PTR_TO_MAP_VALUE_OR_NULL) { 2353 /* Mark all identical map registers in each branch as either 2354 * safe or unknown depending R == 0 or R != 0 conditional. 2355 */ 2356 mark_map_regs(this_branch, insn->dst_reg, 2357 opcode == BPF_JEQ ? PTR_TO_MAP_VALUE : UNKNOWN_VALUE); 2358 mark_map_regs(other_branch, insn->dst_reg, 2359 opcode == BPF_JEQ ? UNKNOWN_VALUE : PTR_TO_MAP_VALUE); 2360 } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT && 2361 dst_reg->type == PTR_TO_PACKET && 2362 regs[insn->src_reg].type == PTR_TO_PACKET_END) { 2363 find_good_pkt_pointers(this_branch, dst_reg); 2364 } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGE && 2365 dst_reg->type == PTR_TO_PACKET_END && 2366 regs[insn->src_reg].type == PTR_TO_PACKET) { 2367 find_good_pkt_pointers(other_branch, ®s[insn->src_reg]); 2368 } else if (is_pointer_value(env, insn->dst_reg)) { 2369 verbose("R%d pointer comparison prohibited\n", insn->dst_reg); 2370 return -EACCES; 2371 } 2372 if (log_level) 2373 print_verifier_state(this_branch); 2374 return 0; 2375 } 2376 2377 /* return the map pointer stored inside BPF_LD_IMM64 instruction */ 2378 static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn) 2379 { 2380 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32; 2381 2382 return (struct bpf_map *) (unsigned long) imm64; 2383 } 2384 2385 /* verify BPF_LD_IMM64 instruction */ 2386 static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn) 2387 { 2388 struct bpf_reg_state *regs = env->cur_state.regs; 2389 int err; 2390 2391 if (BPF_SIZE(insn->code) != BPF_DW) { 2392 verbose("invalid BPF_LD_IMM insn\n"); 2393 return -EINVAL; 2394 } 2395 if (insn->off != 0) { 2396 verbose("BPF_LD_IMM64 uses reserved fields\n"); 2397 return -EINVAL; 2398 } 2399 2400 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 2401 if (err) 2402 return err; 2403 2404 if (insn->src_reg == 0) { 2405 u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm; 2406 2407 regs[insn->dst_reg].type = CONST_IMM; 2408 regs[insn->dst_reg].imm = imm; 2409 return 0; 2410 } 2411 2412 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */ 2413 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD); 2414 2415 regs[insn->dst_reg].type = CONST_PTR_TO_MAP; 2416 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn); 2417 return 0; 2418 } 2419 2420 static bool may_access_skb(enum bpf_prog_type type) 2421 { 2422 switch (type) { 2423 case BPF_PROG_TYPE_SOCKET_FILTER: 2424 case BPF_PROG_TYPE_SCHED_CLS: 2425 case BPF_PROG_TYPE_SCHED_ACT: 2426 return true; 2427 default: 2428 return false; 2429 } 2430 } 2431 2432 /* verify safety of LD_ABS|LD_IND instructions: 2433 * - they can only appear in the programs where ctx == skb 2434 * - since they are wrappers of function calls, they scratch R1-R5 registers, 2435 * preserve R6-R9, and store return value into R0 2436 * 2437 * Implicit input: 2438 * ctx == skb == R6 == CTX 2439 * 2440 * Explicit input: 2441 * SRC == any register 2442 * IMM == 32-bit immediate 2443 * 2444 * Output: 2445 * R0 - 8/16/32-bit skb data converted to cpu endianness 2446 */ 2447 static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn) 2448 { 2449 struct bpf_reg_state *regs = env->cur_state.regs; 2450 u8 mode = BPF_MODE(insn->code); 2451 struct bpf_reg_state *reg; 2452 int i, err; 2453 2454 if (!may_access_skb(env->prog->type)) { 2455 verbose("BPF_LD_[ABS|IND] instructions not allowed for this program type\n"); 2456 return -EINVAL; 2457 } 2458 2459 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 || 2460 BPF_SIZE(insn->code) == BPF_DW || 2461 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) { 2462 verbose("BPF_LD_[ABS|IND] uses reserved fields\n"); 2463 return -EINVAL; 2464 } 2465 2466 /* check whether implicit source operand (register R6) is readable */ 2467 err = check_reg_arg(regs, BPF_REG_6, SRC_OP); 2468 if (err) 2469 return err; 2470 2471 if (regs[BPF_REG_6].type != PTR_TO_CTX) { 2472 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n"); 2473 return -EINVAL; 2474 } 2475 2476 if (mode == BPF_IND) { 2477 /* check explicit source operand */ 2478 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2479 if (err) 2480 return err; 2481 } 2482 2483 /* reset caller saved regs to unreadable */ 2484 for (i = 0; i < CALLER_SAVED_REGS; i++) { 2485 reg = regs + caller_saved[i]; 2486 reg->type = NOT_INIT; 2487 reg->imm = 0; 2488 } 2489 2490 /* mark destination R0 register as readable, since it contains 2491 * the value fetched from the packet 2492 */ 2493 regs[BPF_REG_0].type = UNKNOWN_VALUE; 2494 return 0; 2495 } 2496 2497 /* non-recursive DFS pseudo code 2498 * 1 procedure DFS-iterative(G,v): 2499 * 2 label v as discovered 2500 * 3 let S be a stack 2501 * 4 S.push(v) 2502 * 5 while S is not empty 2503 * 6 t <- S.pop() 2504 * 7 if t is what we're looking for: 2505 * 8 return t 2506 * 9 for all edges e in G.adjacentEdges(t) do 2507 * 10 if edge e is already labelled 2508 * 11 continue with the next edge 2509 * 12 w <- G.adjacentVertex(t,e) 2510 * 13 if vertex w is not discovered and not explored 2511 * 14 label e as tree-edge 2512 * 15 label w as discovered 2513 * 16 S.push(w) 2514 * 17 continue at 5 2515 * 18 else if vertex w is discovered 2516 * 19 label e as back-edge 2517 * 20 else 2518 * 21 // vertex w is explored 2519 * 22 label e as forward- or cross-edge 2520 * 23 label t as explored 2521 * 24 S.pop() 2522 * 2523 * convention: 2524 * 0x10 - discovered 2525 * 0x11 - discovered and fall-through edge labelled 2526 * 0x12 - discovered and fall-through and branch edges labelled 2527 * 0x20 - explored 2528 */ 2529 2530 enum { 2531 DISCOVERED = 0x10, 2532 EXPLORED = 0x20, 2533 FALLTHROUGH = 1, 2534 BRANCH = 2, 2535 }; 2536 2537 #define STATE_LIST_MARK ((struct bpf_verifier_state_list *) -1L) 2538 2539 static int *insn_stack; /* stack of insns to process */ 2540 static int cur_stack; /* current stack index */ 2541 static int *insn_state; 2542 2543 /* t, w, e - match pseudo-code above: 2544 * t - index of current instruction 2545 * w - next instruction 2546 * e - edge 2547 */ 2548 static int push_insn(int t, int w, int e, struct bpf_verifier_env *env) 2549 { 2550 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH)) 2551 return 0; 2552 2553 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH)) 2554 return 0; 2555 2556 if (w < 0 || w >= env->prog->len) { 2557 verbose("jump out of range from insn %d to %d\n", t, w); 2558 return -EINVAL; 2559 } 2560 2561 if (e == BRANCH) 2562 /* mark branch target for state pruning */ 2563 env->explored_states[w] = STATE_LIST_MARK; 2564 2565 if (insn_state[w] == 0) { 2566 /* tree-edge */ 2567 insn_state[t] = DISCOVERED | e; 2568 insn_state[w] = DISCOVERED; 2569 if (cur_stack >= env->prog->len) 2570 return -E2BIG; 2571 insn_stack[cur_stack++] = w; 2572 return 1; 2573 } else if ((insn_state[w] & 0xF0) == DISCOVERED) { 2574 verbose("back-edge from insn %d to %d\n", t, w); 2575 return -EINVAL; 2576 } else if (insn_state[w] == EXPLORED) { 2577 /* forward- or cross-edge */ 2578 insn_state[t] = DISCOVERED | e; 2579 } else { 2580 verbose("insn state internal bug\n"); 2581 return -EFAULT; 2582 } 2583 return 0; 2584 } 2585 2586 /* non-recursive depth-first-search to detect loops in BPF program 2587 * loop == back-edge in directed graph 2588 */ 2589 static int check_cfg(struct bpf_verifier_env *env) 2590 { 2591 struct bpf_insn *insns = env->prog->insnsi; 2592 int insn_cnt = env->prog->len; 2593 int ret = 0; 2594 int i, t; 2595 2596 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 2597 if (!insn_state) 2598 return -ENOMEM; 2599 2600 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 2601 if (!insn_stack) { 2602 kfree(insn_state); 2603 return -ENOMEM; 2604 } 2605 2606 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */ 2607 insn_stack[0] = 0; /* 0 is the first instruction */ 2608 cur_stack = 1; 2609 2610 peek_stack: 2611 if (cur_stack == 0) 2612 goto check_state; 2613 t = insn_stack[cur_stack - 1]; 2614 2615 if (BPF_CLASS(insns[t].code) == BPF_JMP) { 2616 u8 opcode = BPF_OP(insns[t].code); 2617 2618 if (opcode == BPF_EXIT) { 2619 goto mark_explored; 2620 } else if (opcode == BPF_CALL) { 2621 ret = push_insn(t, t + 1, FALLTHROUGH, env); 2622 if (ret == 1) 2623 goto peek_stack; 2624 else if (ret < 0) 2625 goto err_free; 2626 if (t + 1 < insn_cnt) 2627 env->explored_states[t + 1] = STATE_LIST_MARK; 2628 } else if (opcode == BPF_JA) { 2629 if (BPF_SRC(insns[t].code) != BPF_K) { 2630 ret = -EINVAL; 2631 goto err_free; 2632 } 2633 /* unconditional jump with single edge */ 2634 ret = push_insn(t, t + insns[t].off + 1, 2635 FALLTHROUGH, env); 2636 if (ret == 1) 2637 goto peek_stack; 2638 else if (ret < 0) 2639 goto err_free; 2640 /* tell verifier to check for equivalent states 2641 * after every call and jump 2642 */ 2643 if (t + 1 < insn_cnt) 2644 env->explored_states[t + 1] = STATE_LIST_MARK; 2645 } else { 2646 /* conditional jump with two edges */ 2647 env->explored_states[t] = STATE_LIST_MARK; 2648 ret = push_insn(t, t + 1, FALLTHROUGH, env); 2649 if (ret == 1) 2650 goto peek_stack; 2651 else if (ret < 0) 2652 goto err_free; 2653 2654 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env); 2655 if (ret == 1) 2656 goto peek_stack; 2657 else if (ret < 0) 2658 goto err_free; 2659 } 2660 } else { 2661 /* all other non-branch instructions with single 2662 * fall-through edge 2663 */ 2664 ret = push_insn(t, t + 1, FALLTHROUGH, env); 2665 if (ret == 1) 2666 goto peek_stack; 2667 else if (ret < 0) 2668 goto err_free; 2669 } 2670 2671 mark_explored: 2672 insn_state[t] = EXPLORED; 2673 if (cur_stack-- <= 0) { 2674 verbose("pop stack internal bug\n"); 2675 ret = -EFAULT; 2676 goto err_free; 2677 } 2678 goto peek_stack; 2679 2680 check_state: 2681 for (i = 0; i < insn_cnt; i++) { 2682 if (insn_state[i] != EXPLORED) { 2683 verbose("unreachable insn %d\n", i); 2684 ret = -EINVAL; 2685 goto err_free; 2686 } 2687 } 2688 ret = 0; /* cfg looks good */ 2689 2690 err_free: 2691 kfree(insn_state); 2692 kfree(insn_stack); 2693 return ret; 2694 } 2695 2696 /* the following conditions reduce the number of explored insns 2697 * from ~140k to ~80k for ultra large programs that use a lot of ptr_to_packet 2698 */ 2699 static bool compare_ptrs_to_packet(struct bpf_reg_state *old, 2700 struct bpf_reg_state *cur) 2701 { 2702 if (old->id != cur->id) 2703 return false; 2704 2705 /* old ptr_to_packet is more conservative, since it allows smaller 2706 * range. Ex: 2707 * old(off=0,r=10) is equal to cur(off=0,r=20), because 2708 * old(off=0,r=10) means that with range=10 the verifier proceeded 2709 * further and found no issues with the program. Now we're in the same 2710 * spot with cur(off=0,r=20), so we're safe too, since anything further 2711 * will only be looking at most 10 bytes after this pointer. 2712 */ 2713 if (old->off == cur->off && old->range < cur->range) 2714 return true; 2715 2716 /* old(off=20,r=10) is equal to cur(off=22,re=22 or 5 or 0) 2717 * since both cannot be used for packet access and safe(old) 2718 * pointer has smaller off that could be used for further 2719 * 'if (ptr > data_end)' check 2720 * Ex: 2721 * old(off=20,r=10) and cur(off=22,r=22) and cur(off=22,r=0) mean 2722 * that we cannot access the packet. 2723 * The safe range is: 2724 * [ptr, ptr + range - off) 2725 * so whenever off >=range, it means no safe bytes from this pointer. 2726 * When comparing old->off <= cur->off, it means that older code 2727 * went with smaller offset and that offset was later 2728 * used to figure out the safe range after 'if (ptr > data_end)' check 2729 * Say, 'old' state was explored like: 2730 * ... R3(off=0, r=0) 2731 * R4 = R3 + 20 2732 * ... now R4(off=20,r=0) <-- here 2733 * if (R4 > data_end) 2734 * ... R4(off=20,r=20), R3(off=0,r=20) and R3 can be used to access. 2735 * ... the code further went all the way to bpf_exit. 2736 * Now the 'cur' state at the mark 'here' has R4(off=30,r=0). 2737 * old_R4(off=20,r=0) equal to cur_R4(off=30,r=0), since if the verifier 2738 * goes further, such cur_R4 will give larger safe packet range after 2739 * 'if (R4 > data_end)' and all further insn were already good with r=20, 2740 * so they will be good with r=30 and we can prune the search. 2741 */ 2742 if (old->off <= cur->off && 2743 old->off >= old->range && cur->off >= cur->range) 2744 return true; 2745 2746 return false; 2747 } 2748 2749 /* compare two verifier states 2750 * 2751 * all states stored in state_list are known to be valid, since 2752 * verifier reached 'bpf_exit' instruction through them 2753 * 2754 * this function is called when verifier exploring different branches of 2755 * execution popped from the state stack. If it sees an old state that has 2756 * more strict register state and more strict stack state then this execution 2757 * branch doesn't need to be explored further, since verifier already 2758 * concluded that more strict state leads to valid finish. 2759 * 2760 * Therefore two states are equivalent if register state is more conservative 2761 * and explored stack state is more conservative than the current one. 2762 * Example: 2763 * explored current 2764 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC) 2765 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC) 2766 * 2767 * In other words if current stack state (one being explored) has more 2768 * valid slots than old one that already passed validation, it means 2769 * the verifier can stop exploring and conclude that current state is valid too 2770 * 2771 * Similarly with registers. If explored state has register type as invalid 2772 * whereas register type in current state is meaningful, it means that 2773 * the current state will reach 'bpf_exit' instruction safely 2774 */ 2775 static bool states_equal(struct bpf_verifier_env *env, 2776 struct bpf_verifier_state *old, 2777 struct bpf_verifier_state *cur) 2778 { 2779 bool varlen_map_access = env->varlen_map_value_access; 2780 struct bpf_reg_state *rold, *rcur; 2781 int i; 2782 2783 for (i = 0; i < MAX_BPF_REG; i++) { 2784 rold = &old->regs[i]; 2785 rcur = &cur->regs[i]; 2786 2787 if (memcmp(rold, rcur, sizeof(*rold)) == 0) 2788 continue; 2789 2790 /* If the ranges were not the same, but everything else was and 2791 * we didn't do a variable access into a map then we are a-ok. 2792 */ 2793 if (!varlen_map_access && 2794 memcmp(rold, rcur, offsetofend(struct bpf_reg_state, id)) == 0) 2795 continue; 2796 2797 /* If we didn't map access then again we don't care about the 2798 * mismatched range values and it's ok if our old type was 2799 * UNKNOWN and we didn't go to a NOT_INIT'ed reg. 2800 */ 2801 if (rold->type == NOT_INIT || 2802 (!varlen_map_access && rold->type == UNKNOWN_VALUE && 2803 rcur->type != NOT_INIT)) 2804 continue; 2805 2806 /* Don't care about the reg->id in this case. */ 2807 if (rold->type == PTR_TO_MAP_VALUE_OR_NULL && 2808 rcur->type == PTR_TO_MAP_VALUE_OR_NULL && 2809 rold->map_ptr == rcur->map_ptr) 2810 continue; 2811 2812 if (rold->type == PTR_TO_PACKET && rcur->type == PTR_TO_PACKET && 2813 compare_ptrs_to_packet(rold, rcur)) 2814 continue; 2815 2816 return false; 2817 } 2818 2819 for (i = 0; i < MAX_BPF_STACK; i++) { 2820 if (old->stack_slot_type[i] == STACK_INVALID) 2821 continue; 2822 if (old->stack_slot_type[i] != cur->stack_slot_type[i]) 2823 /* Ex: old explored (safe) state has STACK_SPILL in 2824 * this stack slot, but current has has STACK_MISC -> 2825 * this verifier states are not equivalent, 2826 * return false to continue verification of this path 2827 */ 2828 return false; 2829 if (i % BPF_REG_SIZE) 2830 continue; 2831 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE], 2832 &cur->spilled_regs[i / BPF_REG_SIZE], 2833 sizeof(old->spilled_regs[0]))) 2834 /* when explored and current stack slot types are 2835 * the same, check that stored pointers types 2836 * are the same as well. 2837 * Ex: explored safe path could have stored 2838 * (bpf_reg_state) {.type = PTR_TO_STACK, .imm = -8} 2839 * but current path has stored: 2840 * (bpf_reg_state) {.type = PTR_TO_STACK, .imm = -16} 2841 * such verifier states are not equivalent. 2842 * return false to continue verification of this path 2843 */ 2844 return false; 2845 else 2846 continue; 2847 } 2848 return true; 2849 } 2850 2851 static int is_state_visited(struct bpf_verifier_env *env, int insn_idx) 2852 { 2853 struct bpf_verifier_state_list *new_sl; 2854 struct bpf_verifier_state_list *sl; 2855 2856 sl = env->explored_states[insn_idx]; 2857 if (!sl) 2858 /* this 'insn_idx' instruction wasn't marked, so we will not 2859 * be doing state search here 2860 */ 2861 return 0; 2862 2863 while (sl != STATE_LIST_MARK) { 2864 if (states_equal(env, &sl->state, &env->cur_state)) 2865 /* reached equivalent register/stack state, 2866 * prune the search 2867 */ 2868 return 1; 2869 sl = sl->next; 2870 } 2871 2872 /* there were no equivalent states, remember current one. 2873 * technically the current state is not proven to be safe yet, 2874 * but it will either reach bpf_exit (which means it's safe) or 2875 * it will be rejected. Since there are no loops, we won't be 2876 * seeing this 'insn_idx' instruction again on the way to bpf_exit 2877 */ 2878 new_sl = kmalloc(sizeof(struct bpf_verifier_state_list), GFP_USER); 2879 if (!new_sl) 2880 return -ENOMEM; 2881 2882 /* add new state to the head of linked list */ 2883 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state)); 2884 new_sl->next = env->explored_states[insn_idx]; 2885 env->explored_states[insn_idx] = new_sl; 2886 return 0; 2887 } 2888 2889 static int ext_analyzer_insn_hook(struct bpf_verifier_env *env, 2890 int insn_idx, int prev_insn_idx) 2891 { 2892 if (!env->analyzer_ops || !env->analyzer_ops->insn_hook) 2893 return 0; 2894 2895 return env->analyzer_ops->insn_hook(env, insn_idx, prev_insn_idx); 2896 } 2897 2898 static int do_check(struct bpf_verifier_env *env) 2899 { 2900 struct bpf_verifier_state *state = &env->cur_state; 2901 struct bpf_insn *insns = env->prog->insnsi; 2902 struct bpf_reg_state *regs = state->regs; 2903 int insn_cnt = env->prog->len; 2904 int insn_idx, prev_insn_idx = 0; 2905 int insn_processed = 0; 2906 bool do_print_state = false; 2907 2908 init_reg_state(regs); 2909 insn_idx = 0; 2910 env->varlen_map_value_access = false; 2911 for (;;) { 2912 struct bpf_insn *insn; 2913 u8 class; 2914 int err; 2915 2916 if (insn_idx >= insn_cnt) { 2917 verbose("invalid insn idx %d insn_cnt %d\n", 2918 insn_idx, insn_cnt); 2919 return -EFAULT; 2920 } 2921 2922 insn = &insns[insn_idx]; 2923 class = BPF_CLASS(insn->code); 2924 2925 if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) { 2926 verbose("BPF program is too large. Processed %d insn\n", 2927 insn_processed); 2928 return -E2BIG; 2929 } 2930 2931 err = is_state_visited(env, insn_idx); 2932 if (err < 0) 2933 return err; 2934 if (err == 1) { 2935 /* found equivalent state, can prune the search */ 2936 if (log_level) { 2937 if (do_print_state) 2938 verbose("\nfrom %d to %d: safe\n", 2939 prev_insn_idx, insn_idx); 2940 else 2941 verbose("%d: safe\n", insn_idx); 2942 } 2943 goto process_bpf_exit; 2944 } 2945 2946 if (need_resched()) 2947 cond_resched(); 2948 2949 if (log_level > 1 || (log_level && do_print_state)) { 2950 if (log_level > 1) 2951 verbose("%d:", insn_idx); 2952 else 2953 verbose("\nfrom %d to %d:", 2954 prev_insn_idx, insn_idx); 2955 print_verifier_state(&env->cur_state); 2956 do_print_state = false; 2957 } 2958 2959 if (log_level) { 2960 verbose("%d: ", insn_idx); 2961 print_bpf_insn(env, insn); 2962 } 2963 2964 err = ext_analyzer_insn_hook(env, insn_idx, prev_insn_idx); 2965 if (err) 2966 return err; 2967 2968 if (class == BPF_ALU || class == BPF_ALU64) { 2969 err = check_alu_op(env, insn); 2970 if (err) 2971 return err; 2972 2973 } else if (class == BPF_LDX) { 2974 enum bpf_reg_type *prev_src_type, src_reg_type; 2975 2976 /* check for reserved fields is already done */ 2977 2978 /* check src operand */ 2979 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2980 if (err) 2981 return err; 2982 2983 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); 2984 if (err) 2985 return err; 2986 2987 src_reg_type = regs[insn->src_reg].type; 2988 2989 /* check that memory (src_reg + off) is readable, 2990 * the state of dst_reg will be updated by this func 2991 */ 2992 err = check_mem_access(env, insn->src_reg, insn->off, 2993 BPF_SIZE(insn->code), BPF_READ, 2994 insn->dst_reg); 2995 if (err) 2996 return err; 2997 2998 if (BPF_SIZE(insn->code) != BPF_W && 2999 BPF_SIZE(insn->code) != BPF_DW) { 3000 insn_idx++; 3001 continue; 3002 } 3003 3004 prev_src_type = &env->insn_aux_data[insn_idx].ptr_type; 3005 3006 if (*prev_src_type == NOT_INIT) { 3007 /* saw a valid insn 3008 * dst_reg = *(u32 *)(src_reg + off) 3009 * save type to validate intersecting paths 3010 */ 3011 *prev_src_type = src_reg_type; 3012 3013 } else if (src_reg_type != *prev_src_type && 3014 (src_reg_type == PTR_TO_CTX || 3015 *prev_src_type == PTR_TO_CTX)) { 3016 /* ABuser program is trying to use the same insn 3017 * dst_reg = *(u32*) (src_reg + off) 3018 * with different pointer types: 3019 * src_reg == ctx in one branch and 3020 * src_reg == stack|map in some other branch. 3021 * Reject it. 3022 */ 3023 verbose("same insn cannot be used with different pointers\n"); 3024 return -EINVAL; 3025 } 3026 3027 } else if (class == BPF_STX) { 3028 enum bpf_reg_type *prev_dst_type, dst_reg_type; 3029 3030 if (BPF_MODE(insn->code) == BPF_XADD) { 3031 err = check_xadd(env, insn); 3032 if (err) 3033 return err; 3034 insn_idx++; 3035 continue; 3036 } 3037 3038 /* check src1 operand */ 3039 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 3040 if (err) 3041 return err; 3042 /* check src2 operand */ 3043 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 3044 if (err) 3045 return err; 3046 3047 dst_reg_type = regs[insn->dst_reg].type; 3048 3049 /* check that memory (dst_reg + off) is writeable */ 3050 err = check_mem_access(env, insn->dst_reg, insn->off, 3051 BPF_SIZE(insn->code), BPF_WRITE, 3052 insn->src_reg); 3053 if (err) 3054 return err; 3055 3056 prev_dst_type = &env->insn_aux_data[insn_idx].ptr_type; 3057 3058 if (*prev_dst_type == NOT_INIT) { 3059 *prev_dst_type = dst_reg_type; 3060 } else if (dst_reg_type != *prev_dst_type && 3061 (dst_reg_type == PTR_TO_CTX || 3062 *prev_dst_type == PTR_TO_CTX)) { 3063 verbose("same insn cannot be used with different pointers\n"); 3064 return -EINVAL; 3065 } 3066 3067 } else if (class == BPF_ST) { 3068 if (BPF_MODE(insn->code) != BPF_MEM || 3069 insn->src_reg != BPF_REG_0) { 3070 verbose("BPF_ST uses reserved fields\n"); 3071 return -EINVAL; 3072 } 3073 /* check src operand */ 3074 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 3075 if (err) 3076 return err; 3077 3078 /* check that memory (dst_reg + off) is writeable */ 3079 err = check_mem_access(env, insn->dst_reg, insn->off, 3080 BPF_SIZE(insn->code), BPF_WRITE, 3081 -1); 3082 if (err) 3083 return err; 3084 3085 } else if (class == BPF_JMP) { 3086 u8 opcode = BPF_OP(insn->code); 3087 3088 if (opcode == BPF_CALL) { 3089 if (BPF_SRC(insn->code) != BPF_K || 3090 insn->off != 0 || 3091 insn->src_reg != BPF_REG_0 || 3092 insn->dst_reg != BPF_REG_0) { 3093 verbose("BPF_CALL uses reserved fields\n"); 3094 return -EINVAL; 3095 } 3096 3097 err = check_call(env, insn->imm, insn_idx); 3098 if (err) 3099 return err; 3100 3101 } else if (opcode == BPF_JA) { 3102 if (BPF_SRC(insn->code) != BPF_K || 3103 insn->imm != 0 || 3104 insn->src_reg != BPF_REG_0 || 3105 insn->dst_reg != BPF_REG_0) { 3106 verbose("BPF_JA uses reserved fields\n"); 3107 return -EINVAL; 3108 } 3109 3110 insn_idx += insn->off + 1; 3111 continue; 3112 3113 } else if (opcode == BPF_EXIT) { 3114 if (BPF_SRC(insn->code) != BPF_K || 3115 insn->imm != 0 || 3116 insn->src_reg != BPF_REG_0 || 3117 insn->dst_reg != BPF_REG_0) { 3118 verbose("BPF_EXIT uses reserved fields\n"); 3119 return -EINVAL; 3120 } 3121 3122 /* eBPF calling convetion is such that R0 is used 3123 * to return the value from eBPF program. 3124 * Make sure that it's readable at this time 3125 * of bpf_exit, which means that program wrote 3126 * something into it earlier 3127 */ 3128 err = check_reg_arg(regs, BPF_REG_0, SRC_OP); 3129 if (err) 3130 return err; 3131 3132 if (is_pointer_value(env, BPF_REG_0)) { 3133 verbose("R0 leaks addr as return value\n"); 3134 return -EACCES; 3135 } 3136 3137 process_bpf_exit: 3138 insn_idx = pop_stack(env, &prev_insn_idx); 3139 if (insn_idx < 0) { 3140 break; 3141 } else { 3142 do_print_state = true; 3143 continue; 3144 } 3145 } else { 3146 err = check_cond_jmp_op(env, insn, &insn_idx); 3147 if (err) 3148 return err; 3149 } 3150 } else if (class == BPF_LD) { 3151 u8 mode = BPF_MODE(insn->code); 3152 3153 if (mode == BPF_ABS || mode == BPF_IND) { 3154 err = check_ld_abs(env, insn); 3155 if (err) 3156 return err; 3157 3158 } else if (mode == BPF_IMM) { 3159 err = check_ld_imm(env, insn); 3160 if (err) 3161 return err; 3162 3163 insn_idx++; 3164 } else { 3165 verbose("invalid BPF_LD mode\n"); 3166 return -EINVAL; 3167 } 3168 reset_reg_range_values(regs, insn->dst_reg); 3169 } else { 3170 verbose("unknown insn class %d\n", class); 3171 return -EINVAL; 3172 } 3173 3174 insn_idx++; 3175 } 3176 3177 verbose("processed %d insns\n", insn_processed); 3178 return 0; 3179 } 3180 3181 static int check_map_prealloc(struct bpf_map *map) 3182 { 3183 return (map->map_type != BPF_MAP_TYPE_HASH && 3184 map->map_type != BPF_MAP_TYPE_PERCPU_HASH && 3185 map->map_type != BPF_MAP_TYPE_HASH_OF_MAPS) || 3186 !(map->map_flags & BPF_F_NO_PREALLOC); 3187 } 3188 3189 static int check_map_prog_compatibility(struct bpf_map *map, 3190 struct bpf_prog *prog) 3191 3192 { 3193 /* Make sure that BPF_PROG_TYPE_PERF_EVENT programs only use 3194 * preallocated hash maps, since doing memory allocation 3195 * in overflow_handler can crash depending on where nmi got 3196 * triggered. 3197 */ 3198 if (prog->type == BPF_PROG_TYPE_PERF_EVENT) { 3199 if (!check_map_prealloc(map)) { 3200 verbose("perf_event programs can only use preallocated hash map\n"); 3201 return -EINVAL; 3202 } 3203 if (map->inner_map_meta && 3204 !check_map_prealloc(map->inner_map_meta)) { 3205 verbose("perf_event programs can only use preallocated inner hash map\n"); 3206 return -EINVAL; 3207 } 3208 } 3209 return 0; 3210 } 3211 3212 /* look for pseudo eBPF instructions that access map FDs and 3213 * replace them with actual map pointers 3214 */ 3215 static int replace_map_fd_with_map_ptr(struct bpf_verifier_env *env) 3216 { 3217 struct bpf_insn *insn = env->prog->insnsi; 3218 int insn_cnt = env->prog->len; 3219 int i, j, err; 3220 3221 err = bpf_prog_calc_tag(env->prog); 3222 if (err) 3223 return err; 3224 3225 for (i = 0; i < insn_cnt; i++, insn++) { 3226 if (BPF_CLASS(insn->code) == BPF_LDX && 3227 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) { 3228 verbose("BPF_LDX uses reserved fields\n"); 3229 return -EINVAL; 3230 } 3231 3232 if (BPF_CLASS(insn->code) == BPF_STX && 3233 ((BPF_MODE(insn->code) != BPF_MEM && 3234 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) { 3235 verbose("BPF_STX uses reserved fields\n"); 3236 return -EINVAL; 3237 } 3238 3239 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) { 3240 struct bpf_map *map; 3241 struct fd f; 3242 3243 if (i == insn_cnt - 1 || insn[1].code != 0 || 3244 insn[1].dst_reg != 0 || insn[1].src_reg != 0 || 3245 insn[1].off != 0) { 3246 verbose("invalid bpf_ld_imm64 insn\n"); 3247 return -EINVAL; 3248 } 3249 3250 if (insn->src_reg == 0) 3251 /* valid generic load 64-bit imm */ 3252 goto next_insn; 3253 3254 if (insn->src_reg != BPF_PSEUDO_MAP_FD) { 3255 verbose("unrecognized bpf_ld_imm64 insn\n"); 3256 return -EINVAL; 3257 } 3258 3259 f = fdget(insn->imm); 3260 map = __bpf_map_get(f); 3261 if (IS_ERR(map)) { 3262 verbose("fd %d is not pointing to valid bpf_map\n", 3263 insn->imm); 3264 return PTR_ERR(map); 3265 } 3266 3267 err = check_map_prog_compatibility(map, env->prog); 3268 if (err) { 3269 fdput(f); 3270 return err; 3271 } 3272 3273 /* store map pointer inside BPF_LD_IMM64 instruction */ 3274 insn[0].imm = (u32) (unsigned long) map; 3275 insn[1].imm = ((u64) (unsigned long) map) >> 32; 3276 3277 /* check whether we recorded this map already */ 3278 for (j = 0; j < env->used_map_cnt; j++) 3279 if (env->used_maps[j] == map) { 3280 fdput(f); 3281 goto next_insn; 3282 } 3283 3284 if (env->used_map_cnt >= MAX_USED_MAPS) { 3285 fdput(f); 3286 return -E2BIG; 3287 } 3288 3289 /* hold the map. If the program is rejected by verifier, 3290 * the map will be released by release_maps() or it 3291 * will be used by the valid program until it's unloaded 3292 * and all maps are released in free_bpf_prog_info() 3293 */ 3294 map = bpf_map_inc(map, false); 3295 if (IS_ERR(map)) { 3296 fdput(f); 3297 return PTR_ERR(map); 3298 } 3299 env->used_maps[env->used_map_cnt++] = map; 3300 3301 fdput(f); 3302 next_insn: 3303 insn++; 3304 i++; 3305 } 3306 } 3307 3308 /* now all pseudo BPF_LD_IMM64 instructions load valid 3309 * 'struct bpf_map *' into a register instead of user map_fd. 3310 * These pointers will be used later by verifier to validate map access. 3311 */ 3312 return 0; 3313 } 3314 3315 /* drop refcnt of maps used by the rejected program */ 3316 static void release_maps(struct bpf_verifier_env *env) 3317 { 3318 int i; 3319 3320 for (i = 0; i < env->used_map_cnt; i++) 3321 bpf_map_put(env->used_maps[i]); 3322 } 3323 3324 /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */ 3325 static void convert_pseudo_ld_imm64(struct bpf_verifier_env *env) 3326 { 3327 struct bpf_insn *insn = env->prog->insnsi; 3328 int insn_cnt = env->prog->len; 3329 int i; 3330 3331 for (i = 0; i < insn_cnt; i++, insn++) 3332 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW)) 3333 insn->src_reg = 0; 3334 } 3335 3336 /* single env->prog->insni[off] instruction was replaced with the range 3337 * insni[off, off + cnt). Adjust corresponding insn_aux_data by copying 3338 * [0, off) and [off, end) to new locations, so the patched range stays zero 3339 */ 3340 static int adjust_insn_aux_data(struct bpf_verifier_env *env, u32 prog_len, 3341 u32 off, u32 cnt) 3342 { 3343 struct bpf_insn_aux_data *new_data, *old_data = env->insn_aux_data; 3344 3345 if (cnt == 1) 3346 return 0; 3347 new_data = vzalloc(sizeof(struct bpf_insn_aux_data) * prog_len); 3348 if (!new_data) 3349 return -ENOMEM; 3350 memcpy(new_data, old_data, sizeof(struct bpf_insn_aux_data) * off); 3351 memcpy(new_data + off + cnt - 1, old_data + off, 3352 sizeof(struct bpf_insn_aux_data) * (prog_len - off - cnt + 1)); 3353 env->insn_aux_data = new_data; 3354 vfree(old_data); 3355 return 0; 3356 } 3357 3358 static struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 off, 3359 const struct bpf_insn *patch, u32 len) 3360 { 3361 struct bpf_prog *new_prog; 3362 3363 new_prog = bpf_patch_insn_single(env->prog, off, patch, len); 3364 if (!new_prog) 3365 return NULL; 3366 if (adjust_insn_aux_data(env, new_prog->len, off, len)) 3367 return NULL; 3368 return new_prog; 3369 } 3370 3371 /* convert load instructions that access fields of 'struct __sk_buff' 3372 * into sequence of instructions that access fields of 'struct sk_buff' 3373 */ 3374 static int convert_ctx_accesses(struct bpf_verifier_env *env) 3375 { 3376 const struct bpf_verifier_ops *ops = env->prog->aux->ops; 3377 const int insn_cnt = env->prog->len; 3378 struct bpf_insn insn_buf[16], *insn; 3379 struct bpf_prog *new_prog; 3380 enum bpf_access_type type; 3381 int i, cnt, delta = 0; 3382 3383 if (ops->gen_prologue) { 3384 cnt = ops->gen_prologue(insn_buf, env->seen_direct_write, 3385 env->prog); 3386 if (cnt >= ARRAY_SIZE(insn_buf)) { 3387 verbose("bpf verifier is misconfigured\n"); 3388 return -EINVAL; 3389 } else if (cnt) { 3390 new_prog = bpf_patch_insn_data(env, 0, insn_buf, cnt); 3391 if (!new_prog) 3392 return -ENOMEM; 3393 3394 env->prog = new_prog; 3395 delta += cnt - 1; 3396 } 3397 } 3398 3399 if (!ops->convert_ctx_access) 3400 return 0; 3401 3402 insn = env->prog->insnsi + delta; 3403 3404 for (i = 0; i < insn_cnt; i++, insn++) { 3405 if (insn->code == (BPF_LDX | BPF_MEM | BPF_B) || 3406 insn->code == (BPF_LDX | BPF_MEM | BPF_H) || 3407 insn->code == (BPF_LDX | BPF_MEM | BPF_W) || 3408 insn->code == (BPF_LDX | BPF_MEM | BPF_DW)) 3409 type = BPF_READ; 3410 else if (insn->code == (BPF_STX | BPF_MEM | BPF_B) || 3411 insn->code == (BPF_STX | BPF_MEM | BPF_H) || 3412 insn->code == (BPF_STX | BPF_MEM | BPF_W) || 3413 insn->code == (BPF_STX | BPF_MEM | BPF_DW)) 3414 type = BPF_WRITE; 3415 else 3416 continue; 3417 3418 if (env->insn_aux_data[i + delta].ptr_type != PTR_TO_CTX) 3419 continue; 3420 3421 cnt = ops->convert_ctx_access(type, insn, insn_buf, env->prog); 3422 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) { 3423 verbose("bpf verifier is misconfigured\n"); 3424 return -EINVAL; 3425 } 3426 3427 new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt); 3428 if (!new_prog) 3429 return -ENOMEM; 3430 3431 delta += cnt - 1; 3432 3433 /* keep walking new program and skip insns we just inserted */ 3434 env->prog = new_prog; 3435 insn = new_prog->insnsi + i + delta; 3436 } 3437 3438 return 0; 3439 } 3440 3441 /* fixup insn->imm field of bpf_call instructions 3442 * and inline eligible helpers as explicit sequence of BPF instructions 3443 * 3444 * this function is called after eBPF program passed verification 3445 */ 3446 static int fixup_bpf_calls(struct bpf_verifier_env *env) 3447 { 3448 struct bpf_prog *prog = env->prog; 3449 struct bpf_insn *insn = prog->insnsi; 3450 const struct bpf_func_proto *fn; 3451 const int insn_cnt = prog->len; 3452 struct bpf_insn insn_buf[16]; 3453 struct bpf_prog *new_prog; 3454 struct bpf_map *map_ptr; 3455 int i, cnt, delta = 0; 3456 3457 for (i = 0; i < insn_cnt; i++, insn++) { 3458 if (insn->code != (BPF_JMP | BPF_CALL)) 3459 continue; 3460 3461 if (insn->imm == BPF_FUNC_get_route_realm) 3462 prog->dst_needed = 1; 3463 if (insn->imm == BPF_FUNC_get_prandom_u32) 3464 bpf_user_rnd_init_once(); 3465 if (insn->imm == BPF_FUNC_tail_call) { 3466 /* If we tail call into other programs, we 3467 * cannot make any assumptions since they can 3468 * be replaced dynamically during runtime in 3469 * the program array. 3470 */ 3471 prog->cb_access = 1; 3472 3473 /* mark bpf_tail_call as different opcode to avoid 3474 * conditional branch in the interpeter for every normal 3475 * call and to prevent accidental JITing by JIT compiler 3476 * that doesn't support bpf_tail_call yet 3477 */ 3478 insn->imm = 0; 3479 insn->code |= BPF_X; 3480 continue; 3481 } 3482 3483 if (ebpf_jit_enabled() && insn->imm == BPF_FUNC_map_lookup_elem) { 3484 map_ptr = env->insn_aux_data[i + delta].map_ptr; 3485 if (map_ptr == BPF_MAP_PTR_POISON || 3486 !map_ptr->ops->map_gen_lookup) 3487 goto patch_call_imm; 3488 3489 cnt = map_ptr->ops->map_gen_lookup(map_ptr, insn_buf); 3490 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) { 3491 verbose("bpf verifier is misconfigured\n"); 3492 return -EINVAL; 3493 } 3494 3495 new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, 3496 cnt); 3497 if (!new_prog) 3498 return -ENOMEM; 3499 3500 delta += cnt - 1; 3501 3502 /* keep walking new program and skip insns we just inserted */ 3503 env->prog = prog = new_prog; 3504 insn = new_prog->insnsi + i + delta; 3505 continue; 3506 } 3507 3508 patch_call_imm: 3509 fn = prog->aux->ops->get_func_proto(insn->imm); 3510 /* all functions that have prototype and verifier allowed 3511 * programs to call them, must be real in-kernel functions 3512 */ 3513 if (!fn->func) { 3514 verbose("kernel subsystem misconfigured func %s#%d\n", 3515 func_id_name(insn->imm), insn->imm); 3516 return -EFAULT; 3517 } 3518 insn->imm = fn->func - __bpf_call_base; 3519 } 3520 3521 return 0; 3522 } 3523 3524 static void free_states(struct bpf_verifier_env *env) 3525 { 3526 struct bpf_verifier_state_list *sl, *sln; 3527 int i; 3528 3529 if (!env->explored_states) 3530 return; 3531 3532 for (i = 0; i < env->prog->len; i++) { 3533 sl = env->explored_states[i]; 3534 3535 if (sl) 3536 while (sl != STATE_LIST_MARK) { 3537 sln = sl->next; 3538 kfree(sl); 3539 sl = sln; 3540 } 3541 } 3542 3543 kfree(env->explored_states); 3544 } 3545 3546 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) 3547 { 3548 char __user *log_ubuf = NULL; 3549 struct bpf_verifier_env *env; 3550 int ret = -EINVAL; 3551 3552 /* 'struct bpf_verifier_env' can be global, but since it's not small, 3553 * allocate/free it every time bpf_check() is called 3554 */ 3555 env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL); 3556 if (!env) 3557 return -ENOMEM; 3558 3559 env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) * 3560 (*prog)->len); 3561 ret = -ENOMEM; 3562 if (!env->insn_aux_data) 3563 goto err_free_env; 3564 env->prog = *prog; 3565 3566 /* grab the mutex to protect few globals used by verifier */ 3567 mutex_lock(&bpf_verifier_lock); 3568 3569 if (attr->log_level || attr->log_buf || attr->log_size) { 3570 /* user requested verbose verifier output 3571 * and supplied buffer to store the verification trace 3572 */ 3573 log_level = attr->log_level; 3574 log_ubuf = (char __user *) (unsigned long) attr->log_buf; 3575 log_size = attr->log_size; 3576 log_len = 0; 3577 3578 ret = -EINVAL; 3579 /* log_* values have to be sane */ 3580 if (log_size < 128 || log_size > UINT_MAX >> 8 || 3581 log_level == 0 || log_ubuf == NULL) 3582 goto err_unlock; 3583 3584 ret = -ENOMEM; 3585 log_buf = vmalloc(log_size); 3586 if (!log_buf) 3587 goto err_unlock; 3588 } else { 3589 log_level = 0; 3590 } 3591 if (attr->prog_flags & BPF_F_STRICT_ALIGNMENT) 3592 env->strict_alignment = true; 3593 else 3594 env->strict_alignment = false; 3595 3596 ret = replace_map_fd_with_map_ptr(env); 3597 if (ret < 0) 3598 goto skip_full_check; 3599 3600 env->explored_states = kcalloc(env->prog->len, 3601 sizeof(struct bpf_verifier_state_list *), 3602 GFP_USER); 3603 ret = -ENOMEM; 3604 if (!env->explored_states) 3605 goto skip_full_check; 3606 3607 ret = check_cfg(env); 3608 if (ret < 0) 3609 goto skip_full_check; 3610 3611 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); 3612 3613 ret = do_check(env); 3614 3615 skip_full_check: 3616 while (pop_stack(env, NULL) >= 0); 3617 free_states(env); 3618 3619 if (ret == 0) 3620 /* program is valid, convert *(u32*)(ctx + off) accesses */ 3621 ret = convert_ctx_accesses(env); 3622 3623 if (ret == 0) 3624 ret = fixup_bpf_calls(env); 3625 3626 if (log_level && log_len >= log_size - 1) { 3627 BUG_ON(log_len >= log_size); 3628 /* verifier log exceeded user supplied buffer */ 3629 ret = -ENOSPC; 3630 /* fall through to return what was recorded */ 3631 } 3632 3633 /* copy verifier log back to user space including trailing zero */ 3634 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) { 3635 ret = -EFAULT; 3636 goto free_log_buf; 3637 } 3638 3639 if (ret == 0 && env->used_map_cnt) { 3640 /* if program passed verifier, update used_maps in bpf_prog_info */ 3641 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt, 3642 sizeof(env->used_maps[0]), 3643 GFP_KERNEL); 3644 3645 if (!env->prog->aux->used_maps) { 3646 ret = -ENOMEM; 3647 goto free_log_buf; 3648 } 3649 3650 memcpy(env->prog->aux->used_maps, env->used_maps, 3651 sizeof(env->used_maps[0]) * env->used_map_cnt); 3652 env->prog->aux->used_map_cnt = env->used_map_cnt; 3653 3654 /* program is valid. Convert pseudo bpf_ld_imm64 into generic 3655 * bpf_ld_imm64 instructions 3656 */ 3657 convert_pseudo_ld_imm64(env); 3658 } 3659 3660 free_log_buf: 3661 if (log_level) 3662 vfree(log_buf); 3663 if (!env->prog->aux->used_maps) 3664 /* if we didn't copy map pointers into bpf_prog_info, release 3665 * them now. Otherwise free_bpf_prog_info() will release them. 3666 */ 3667 release_maps(env); 3668 *prog = env->prog; 3669 err_unlock: 3670 mutex_unlock(&bpf_verifier_lock); 3671 vfree(env->insn_aux_data); 3672 err_free_env: 3673 kfree(env); 3674 return ret; 3675 } 3676 3677 int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops, 3678 void *priv) 3679 { 3680 struct bpf_verifier_env *env; 3681 int ret; 3682 3683 env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL); 3684 if (!env) 3685 return -ENOMEM; 3686 3687 env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) * 3688 prog->len); 3689 ret = -ENOMEM; 3690 if (!env->insn_aux_data) 3691 goto err_free_env; 3692 env->prog = prog; 3693 env->analyzer_ops = ops; 3694 env->analyzer_priv = priv; 3695 3696 /* grab the mutex to protect few globals used by verifier */ 3697 mutex_lock(&bpf_verifier_lock); 3698 3699 log_level = 0; 3700 env->strict_alignment = false; 3701 3702 env->explored_states = kcalloc(env->prog->len, 3703 sizeof(struct bpf_verifier_state_list *), 3704 GFP_KERNEL); 3705 ret = -ENOMEM; 3706 if (!env->explored_states) 3707 goto skip_full_check; 3708 3709 ret = check_cfg(env); 3710 if (ret < 0) 3711 goto skip_full_check; 3712 3713 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); 3714 3715 ret = do_check(env); 3716 3717 skip_full_check: 3718 while (pop_stack(env, NULL) >= 0); 3719 free_states(env); 3720 3721 mutex_unlock(&bpf_verifier_lock); 3722 vfree(env->insn_aux_data); 3723 err_free_env: 3724 kfree(env); 3725 return ret; 3726 } 3727 EXPORT_SYMBOL_GPL(bpf_analyzer); 3728