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 65536 144 #define BPF_COMPLEXITY_LIMIT_STACK 1024 145 146 struct bpf_call_arg_meta { 147 struct bpf_map *map_ptr; 148 bool raw_mode; 149 bool pkt_access; 150 int regno; 151 int access_size; 152 }; 153 154 /* verbose verifier prints what it's seeing 155 * bpf_check() is called under lock, so no race to access these global vars 156 */ 157 static u32 log_level, log_size, log_len; 158 static char *log_buf; 159 160 static DEFINE_MUTEX(bpf_verifier_lock); 161 162 /* log_level controls verbosity level of eBPF verifier. 163 * verbose() is used to dump the verification trace to the log, so the user 164 * can figure out what's wrong with the program 165 */ 166 static __printf(1, 2) void verbose(const char *fmt, ...) 167 { 168 va_list args; 169 170 if (log_level == 0 || log_len >= log_size - 1) 171 return; 172 173 va_start(args, fmt); 174 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args); 175 va_end(args); 176 } 177 178 /* string representation of 'enum bpf_reg_type' */ 179 static const char * const reg_type_str[] = { 180 [NOT_INIT] = "?", 181 [UNKNOWN_VALUE] = "inv", 182 [PTR_TO_CTX] = "ctx", 183 [CONST_PTR_TO_MAP] = "map_ptr", 184 [PTR_TO_MAP_VALUE] = "map_value", 185 [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null", 186 [PTR_TO_MAP_VALUE_ADJ] = "map_value_adj", 187 [FRAME_PTR] = "fp", 188 [PTR_TO_STACK] = "fp", 189 [CONST_IMM] = "imm", 190 [PTR_TO_PACKET] = "pkt", 191 [PTR_TO_PACKET_END] = "pkt_end", 192 }; 193 194 #define __BPF_FUNC_STR_FN(x) [BPF_FUNC_ ## x] = __stringify(bpf_ ## x) 195 static const char * const func_id_str[] = { 196 __BPF_FUNC_MAPPER(__BPF_FUNC_STR_FN) 197 }; 198 #undef __BPF_FUNC_STR_FN 199 200 static const char *func_id_name(int id) 201 { 202 BUILD_BUG_ON(ARRAY_SIZE(func_id_str) != __BPF_FUNC_MAX_ID); 203 204 if (id >= 0 && id < __BPF_FUNC_MAX_ID && func_id_str[id]) 205 return func_id_str[id]; 206 else 207 return "unknown"; 208 } 209 210 static void print_verifier_state(struct bpf_verifier_state *state) 211 { 212 struct bpf_reg_state *reg; 213 enum bpf_reg_type t; 214 int i; 215 216 for (i = 0; i < MAX_BPF_REG; i++) { 217 reg = &state->regs[i]; 218 t = reg->type; 219 if (t == NOT_INIT) 220 continue; 221 verbose(" R%d=%s", i, reg_type_str[t]); 222 if (t == CONST_IMM || t == PTR_TO_STACK) 223 verbose("%lld", reg->imm); 224 else if (t == PTR_TO_PACKET) 225 verbose("(id=%d,off=%d,r=%d)", 226 reg->id, reg->off, reg->range); 227 else if (t == UNKNOWN_VALUE && reg->imm) 228 verbose("%lld", reg->imm); 229 else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE || 230 t == PTR_TO_MAP_VALUE_OR_NULL || 231 t == PTR_TO_MAP_VALUE_ADJ) 232 verbose("(ks=%d,vs=%d,id=%u)", 233 reg->map_ptr->key_size, 234 reg->map_ptr->value_size, 235 reg->id); 236 if (reg->min_value != BPF_REGISTER_MIN_RANGE) 237 verbose(",min_value=%lld", 238 (long long)reg->min_value); 239 if (reg->max_value != BPF_REGISTER_MAX_RANGE) 240 verbose(",max_value=%llu", 241 (unsigned long long)reg->max_value); 242 } 243 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 244 if (state->stack_slot_type[i] == STACK_SPILL) 245 verbose(" fp%d=%s", -MAX_BPF_STACK + i, 246 reg_type_str[state->spilled_regs[i / BPF_REG_SIZE].type]); 247 } 248 verbose("\n"); 249 } 250 251 static const char *const bpf_class_string[] = { 252 [BPF_LD] = "ld", 253 [BPF_LDX] = "ldx", 254 [BPF_ST] = "st", 255 [BPF_STX] = "stx", 256 [BPF_ALU] = "alu", 257 [BPF_JMP] = "jmp", 258 [BPF_RET] = "BUG", 259 [BPF_ALU64] = "alu64", 260 }; 261 262 static const char *const bpf_alu_string[16] = { 263 [BPF_ADD >> 4] = "+=", 264 [BPF_SUB >> 4] = "-=", 265 [BPF_MUL >> 4] = "*=", 266 [BPF_DIV >> 4] = "/=", 267 [BPF_OR >> 4] = "|=", 268 [BPF_AND >> 4] = "&=", 269 [BPF_LSH >> 4] = "<<=", 270 [BPF_RSH >> 4] = ">>=", 271 [BPF_NEG >> 4] = "neg", 272 [BPF_MOD >> 4] = "%=", 273 [BPF_XOR >> 4] = "^=", 274 [BPF_MOV >> 4] = "=", 275 [BPF_ARSH >> 4] = "s>>=", 276 [BPF_END >> 4] = "endian", 277 }; 278 279 static const char *const bpf_ldst_string[] = { 280 [BPF_W >> 3] = "u32", 281 [BPF_H >> 3] = "u16", 282 [BPF_B >> 3] = "u8", 283 [BPF_DW >> 3] = "u64", 284 }; 285 286 static const char *const bpf_jmp_string[16] = { 287 [BPF_JA >> 4] = "jmp", 288 [BPF_JEQ >> 4] = "==", 289 [BPF_JGT >> 4] = ">", 290 [BPF_JGE >> 4] = ">=", 291 [BPF_JSET >> 4] = "&", 292 [BPF_JNE >> 4] = "!=", 293 [BPF_JSGT >> 4] = "s>", 294 [BPF_JSGE >> 4] = "s>=", 295 [BPF_CALL >> 4] = "call", 296 [BPF_EXIT >> 4] = "exit", 297 }; 298 299 static void print_bpf_insn(struct bpf_insn *insn) 300 { 301 u8 class = BPF_CLASS(insn->code); 302 303 if (class == BPF_ALU || class == BPF_ALU64) { 304 if (BPF_SRC(insn->code) == BPF_X) 305 verbose("(%02x) %sr%d %s %sr%d\n", 306 insn->code, class == BPF_ALU ? "(u32) " : "", 307 insn->dst_reg, 308 bpf_alu_string[BPF_OP(insn->code) >> 4], 309 class == BPF_ALU ? "(u32) " : "", 310 insn->src_reg); 311 else 312 verbose("(%02x) %sr%d %s %s%d\n", 313 insn->code, class == BPF_ALU ? "(u32) " : "", 314 insn->dst_reg, 315 bpf_alu_string[BPF_OP(insn->code) >> 4], 316 class == BPF_ALU ? "(u32) " : "", 317 insn->imm); 318 } else if (class == BPF_STX) { 319 if (BPF_MODE(insn->code) == BPF_MEM) 320 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n", 321 insn->code, 322 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 323 insn->dst_reg, 324 insn->off, insn->src_reg); 325 else if (BPF_MODE(insn->code) == BPF_XADD) 326 verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n", 327 insn->code, 328 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 329 insn->dst_reg, insn->off, 330 insn->src_reg); 331 else 332 verbose("BUG_%02x\n", insn->code); 333 } else if (class == BPF_ST) { 334 if (BPF_MODE(insn->code) != BPF_MEM) { 335 verbose("BUG_st_%02x\n", insn->code); 336 return; 337 } 338 verbose("(%02x) *(%s *)(r%d %+d) = %d\n", 339 insn->code, 340 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 341 insn->dst_reg, 342 insn->off, insn->imm); 343 } else if (class == BPF_LDX) { 344 if (BPF_MODE(insn->code) != BPF_MEM) { 345 verbose("BUG_ldx_%02x\n", insn->code); 346 return; 347 } 348 verbose("(%02x) r%d = *(%s *)(r%d %+d)\n", 349 insn->code, insn->dst_reg, 350 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 351 insn->src_reg, insn->off); 352 } else if (class == BPF_LD) { 353 if (BPF_MODE(insn->code) == BPF_ABS) { 354 verbose("(%02x) r0 = *(%s *)skb[%d]\n", 355 insn->code, 356 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 357 insn->imm); 358 } else if (BPF_MODE(insn->code) == BPF_IND) { 359 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n", 360 insn->code, 361 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 362 insn->src_reg, insn->imm); 363 } else if (BPF_MODE(insn->code) == BPF_IMM) { 364 verbose("(%02x) r%d = 0x%x\n", 365 insn->code, insn->dst_reg, insn->imm); 366 } else { 367 verbose("BUG_ld_%02x\n", insn->code); 368 return; 369 } 370 } else if (class == BPF_JMP) { 371 u8 opcode = BPF_OP(insn->code); 372 373 if (opcode == BPF_CALL) { 374 verbose("(%02x) call %s#%d\n", insn->code, 375 func_id_name(insn->imm), insn->imm); 376 } else if (insn->code == (BPF_JMP | BPF_JA)) { 377 verbose("(%02x) goto pc%+d\n", 378 insn->code, insn->off); 379 } else if (insn->code == (BPF_JMP | BPF_EXIT)) { 380 verbose("(%02x) exit\n", insn->code); 381 } else if (BPF_SRC(insn->code) == BPF_X) { 382 verbose("(%02x) if r%d %s r%d goto pc%+d\n", 383 insn->code, insn->dst_reg, 384 bpf_jmp_string[BPF_OP(insn->code) >> 4], 385 insn->src_reg, insn->off); 386 } else { 387 verbose("(%02x) if r%d %s 0x%x goto pc%+d\n", 388 insn->code, insn->dst_reg, 389 bpf_jmp_string[BPF_OP(insn->code) >> 4], 390 insn->imm, insn->off); 391 } 392 } else { 393 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]); 394 } 395 } 396 397 static int pop_stack(struct bpf_verifier_env *env, int *prev_insn_idx) 398 { 399 struct bpf_verifier_stack_elem *elem; 400 int insn_idx; 401 402 if (env->head == NULL) 403 return -1; 404 405 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state)); 406 insn_idx = env->head->insn_idx; 407 if (prev_insn_idx) 408 *prev_insn_idx = env->head->prev_insn_idx; 409 elem = env->head->next; 410 kfree(env->head); 411 env->head = elem; 412 env->stack_size--; 413 return insn_idx; 414 } 415 416 static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env, 417 int insn_idx, int prev_insn_idx) 418 { 419 struct bpf_verifier_stack_elem *elem; 420 421 elem = kmalloc(sizeof(struct bpf_verifier_stack_elem), GFP_KERNEL); 422 if (!elem) 423 goto err; 424 425 memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state)); 426 elem->insn_idx = insn_idx; 427 elem->prev_insn_idx = prev_insn_idx; 428 elem->next = env->head; 429 env->head = elem; 430 env->stack_size++; 431 if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) { 432 verbose("BPF program is too complex\n"); 433 goto err; 434 } 435 return &elem->st; 436 err: 437 /* pop all elements and return */ 438 while (pop_stack(env, NULL) >= 0); 439 return NULL; 440 } 441 442 #define CALLER_SAVED_REGS 6 443 static const int caller_saved[CALLER_SAVED_REGS] = { 444 BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5 445 }; 446 447 static void init_reg_state(struct bpf_reg_state *regs) 448 { 449 int i; 450 451 for (i = 0; i < MAX_BPF_REG; i++) { 452 regs[i].type = NOT_INIT; 453 regs[i].imm = 0; 454 regs[i].min_value = BPF_REGISTER_MIN_RANGE; 455 regs[i].max_value = BPF_REGISTER_MAX_RANGE; 456 } 457 458 /* frame pointer */ 459 regs[BPF_REG_FP].type = FRAME_PTR; 460 461 /* 1st arg to a function */ 462 regs[BPF_REG_1].type = PTR_TO_CTX; 463 } 464 465 static void __mark_reg_unknown_value(struct bpf_reg_state *regs, u32 regno) 466 { 467 regs[regno].type = UNKNOWN_VALUE; 468 regs[regno].id = 0; 469 regs[regno].imm = 0; 470 } 471 472 static void mark_reg_unknown_value(struct bpf_reg_state *regs, u32 regno) 473 { 474 BUG_ON(regno >= MAX_BPF_REG); 475 __mark_reg_unknown_value(regs, regno); 476 } 477 478 static void reset_reg_range_values(struct bpf_reg_state *regs, u32 regno) 479 { 480 regs[regno].min_value = BPF_REGISTER_MIN_RANGE; 481 regs[regno].max_value = BPF_REGISTER_MAX_RANGE; 482 } 483 484 static void mark_reg_unknown_value_and_range(struct bpf_reg_state *regs, 485 u32 regno) 486 { 487 mark_reg_unknown_value(regs, regno); 488 reset_reg_range_values(regs, regno); 489 } 490 491 enum reg_arg_type { 492 SRC_OP, /* register is used as source operand */ 493 DST_OP, /* register is used as destination operand */ 494 DST_OP_NO_MARK /* same as above, check only, don't mark */ 495 }; 496 497 static int check_reg_arg(struct bpf_reg_state *regs, u32 regno, 498 enum reg_arg_type t) 499 { 500 if (regno >= MAX_BPF_REG) { 501 verbose("R%d is invalid\n", regno); 502 return -EINVAL; 503 } 504 505 if (t == SRC_OP) { 506 /* check whether register used as source operand can be read */ 507 if (regs[regno].type == NOT_INIT) { 508 verbose("R%d !read_ok\n", regno); 509 return -EACCES; 510 } 511 } else { 512 /* check whether register used as dest operand can be written to */ 513 if (regno == BPF_REG_FP) { 514 verbose("frame pointer is read only\n"); 515 return -EACCES; 516 } 517 if (t == DST_OP) 518 mark_reg_unknown_value(regs, regno); 519 } 520 return 0; 521 } 522 523 static int bpf_size_to_bytes(int bpf_size) 524 { 525 if (bpf_size == BPF_W) 526 return 4; 527 else if (bpf_size == BPF_H) 528 return 2; 529 else if (bpf_size == BPF_B) 530 return 1; 531 else if (bpf_size == BPF_DW) 532 return 8; 533 else 534 return -EINVAL; 535 } 536 537 static bool is_spillable_regtype(enum bpf_reg_type type) 538 { 539 switch (type) { 540 case PTR_TO_MAP_VALUE: 541 case PTR_TO_MAP_VALUE_OR_NULL: 542 case PTR_TO_MAP_VALUE_ADJ: 543 case PTR_TO_STACK: 544 case PTR_TO_CTX: 545 case PTR_TO_PACKET: 546 case PTR_TO_PACKET_END: 547 case FRAME_PTR: 548 case CONST_PTR_TO_MAP: 549 return true; 550 default: 551 return false; 552 } 553 } 554 555 /* check_stack_read/write functions track spill/fill of registers, 556 * stack boundary and alignment are checked in check_mem_access() 557 */ 558 static int check_stack_write(struct bpf_verifier_state *state, int off, 559 int size, int value_regno) 560 { 561 int i; 562 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0, 563 * so it's aligned access and [off, off + size) are within stack limits 564 */ 565 566 if (value_regno >= 0 && 567 is_spillable_regtype(state->regs[value_regno].type)) { 568 569 /* register containing pointer is being spilled into stack */ 570 if (size != BPF_REG_SIZE) { 571 verbose("invalid size of register spill\n"); 572 return -EACCES; 573 } 574 575 /* save register state */ 576 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = 577 state->regs[value_regno]; 578 579 for (i = 0; i < BPF_REG_SIZE; i++) 580 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL; 581 } else { 582 /* regular write of data into stack */ 583 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = 584 (struct bpf_reg_state) {}; 585 586 for (i = 0; i < size; i++) 587 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC; 588 } 589 return 0; 590 } 591 592 static int check_stack_read(struct bpf_verifier_state *state, int off, int size, 593 int value_regno) 594 { 595 u8 *slot_type; 596 int i; 597 598 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off]; 599 600 if (slot_type[0] == STACK_SPILL) { 601 if (size != BPF_REG_SIZE) { 602 verbose("invalid size of register spill\n"); 603 return -EACCES; 604 } 605 for (i = 1; i < BPF_REG_SIZE; i++) { 606 if (slot_type[i] != STACK_SPILL) { 607 verbose("corrupted spill memory\n"); 608 return -EACCES; 609 } 610 } 611 612 if (value_regno >= 0) 613 /* restore register state from stack */ 614 state->regs[value_regno] = 615 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE]; 616 return 0; 617 } else { 618 for (i = 0; i < size; i++) { 619 if (slot_type[i] != STACK_MISC) { 620 verbose("invalid read from stack off %d+%d size %d\n", 621 off, i, size); 622 return -EACCES; 623 } 624 } 625 if (value_regno >= 0) 626 /* have read misc data from the stack */ 627 mark_reg_unknown_value_and_range(state->regs, 628 value_regno); 629 return 0; 630 } 631 } 632 633 /* check read/write into map element returned by bpf_map_lookup_elem() */ 634 static int check_map_access(struct bpf_verifier_env *env, u32 regno, int off, 635 int size) 636 { 637 struct bpf_map *map = env->cur_state.regs[regno].map_ptr; 638 639 if (off < 0 || size <= 0 || off + size > map->value_size) { 640 verbose("invalid access to map value, value_size=%d off=%d size=%d\n", 641 map->value_size, off, size); 642 return -EACCES; 643 } 644 return 0; 645 } 646 647 /* check read/write into an adjusted map element */ 648 static int check_map_access_adj(struct bpf_verifier_env *env, u32 regno, 649 int off, int size) 650 { 651 struct bpf_verifier_state *state = &env->cur_state; 652 struct bpf_reg_state *reg = &state->regs[regno]; 653 int err; 654 655 /* We adjusted the register to this map value, so we 656 * need to change off and size to min_value and max_value 657 * respectively to make sure our theoretical access will be 658 * safe. 659 */ 660 if (log_level) 661 print_verifier_state(state); 662 env->varlen_map_value_access = true; 663 /* The minimum value is only important with signed 664 * comparisons where we can't assume the floor of a 665 * value is 0. If we are using signed variables for our 666 * index'es we need to make sure that whatever we use 667 * will have a set floor within our range. 668 */ 669 if (reg->min_value < 0) { 670 verbose("R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n", 671 regno); 672 return -EACCES; 673 } 674 err = check_map_access(env, regno, reg->min_value + off, size); 675 if (err) { 676 verbose("R%d min value is outside of the array range\n", 677 regno); 678 return err; 679 } 680 681 /* If we haven't set a max value then we need to bail 682 * since we can't be sure we won't do bad things. 683 */ 684 if (reg->max_value == BPF_REGISTER_MAX_RANGE) { 685 verbose("R%d unbounded memory access, make sure to bounds check any array access into a map\n", 686 regno); 687 return -EACCES; 688 } 689 return check_map_access(env, regno, reg->max_value + off, size); 690 } 691 692 #define MAX_PACKET_OFF 0xffff 693 694 static bool may_access_direct_pkt_data(struct bpf_verifier_env *env, 695 const struct bpf_call_arg_meta *meta, 696 enum bpf_access_type t) 697 { 698 switch (env->prog->type) { 699 case BPF_PROG_TYPE_LWT_IN: 700 case BPF_PROG_TYPE_LWT_OUT: 701 /* dst_input() and dst_output() can't write for now */ 702 if (t == BPF_WRITE) 703 return false; 704 /* fallthrough */ 705 case BPF_PROG_TYPE_SCHED_CLS: 706 case BPF_PROG_TYPE_SCHED_ACT: 707 case BPF_PROG_TYPE_XDP: 708 case BPF_PROG_TYPE_LWT_XMIT: 709 if (meta) 710 return meta->pkt_access; 711 712 env->seen_direct_write = true; 713 return true; 714 default: 715 return false; 716 } 717 } 718 719 static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off, 720 int size) 721 { 722 struct bpf_reg_state *regs = env->cur_state.regs; 723 struct bpf_reg_state *reg = ®s[regno]; 724 725 off += reg->off; 726 if (off < 0 || size <= 0 || off + size > reg->range) { 727 verbose("invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n", 728 off, size, regno, reg->id, reg->off, reg->range); 729 return -EACCES; 730 } 731 return 0; 732 } 733 734 /* check access to 'struct bpf_context' fields */ 735 static int check_ctx_access(struct bpf_verifier_env *env, int off, int size, 736 enum bpf_access_type t, enum bpf_reg_type *reg_type) 737 { 738 /* for analyzer ctx accesses are already validated and converted */ 739 if (env->analyzer_ops) 740 return 0; 741 742 if (env->prog->aux->ops->is_valid_access && 743 env->prog->aux->ops->is_valid_access(off, size, t, reg_type)) { 744 /* remember the offset of last byte accessed in ctx */ 745 if (env->prog->aux->max_ctx_offset < off + size) 746 env->prog->aux->max_ctx_offset = off + size; 747 return 0; 748 } 749 750 verbose("invalid bpf_context access off=%d size=%d\n", off, size); 751 return -EACCES; 752 } 753 754 static bool is_pointer_value(struct bpf_verifier_env *env, int regno) 755 { 756 if (env->allow_ptr_leaks) 757 return false; 758 759 switch (env->cur_state.regs[regno].type) { 760 case UNKNOWN_VALUE: 761 case CONST_IMM: 762 return false; 763 default: 764 return true; 765 } 766 } 767 768 static int check_pkt_ptr_alignment(const struct bpf_reg_state *reg, 769 int off, int size) 770 { 771 if (reg->id && size != 1) { 772 verbose("Unknown alignment. Only byte-sized access allowed in packet access.\n"); 773 return -EACCES; 774 } 775 776 /* skb->data is NET_IP_ALIGN-ed */ 777 if ((NET_IP_ALIGN + reg->off + off) % size != 0) { 778 verbose("misaligned packet access off %d+%d+%d size %d\n", 779 NET_IP_ALIGN, reg->off, off, size); 780 return -EACCES; 781 } 782 783 return 0; 784 } 785 786 static int check_val_ptr_alignment(const struct bpf_reg_state *reg, 787 int size) 788 { 789 if (size != 1) { 790 verbose("Unknown alignment. Only byte-sized access allowed in value access.\n"); 791 return -EACCES; 792 } 793 794 return 0; 795 } 796 797 static int check_ptr_alignment(const struct bpf_reg_state *reg, 798 int off, int size) 799 { 800 switch (reg->type) { 801 case PTR_TO_PACKET: 802 return IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) ? 0 : 803 check_pkt_ptr_alignment(reg, off, size); 804 case PTR_TO_MAP_VALUE_ADJ: 805 return IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) ? 0 : 806 check_val_ptr_alignment(reg, size); 807 default: 808 if (off % size != 0) { 809 verbose("misaligned access off %d size %d\n", 810 off, size); 811 return -EACCES; 812 } 813 814 return 0; 815 } 816 } 817 818 /* check whether memory at (regno + off) is accessible for t = (read | write) 819 * if t==write, value_regno is a register which value is stored into memory 820 * if t==read, value_regno is a register which will receive the value from memory 821 * if t==write && value_regno==-1, some unknown value is stored into memory 822 * if t==read && value_regno==-1, don't care what we read from memory 823 */ 824 static int check_mem_access(struct bpf_verifier_env *env, u32 regno, int off, 825 int bpf_size, enum bpf_access_type t, 826 int value_regno) 827 { 828 struct bpf_verifier_state *state = &env->cur_state; 829 struct bpf_reg_state *reg = &state->regs[regno]; 830 int size, err = 0; 831 832 if (reg->type == PTR_TO_STACK) 833 off += reg->imm; 834 835 size = bpf_size_to_bytes(bpf_size); 836 if (size < 0) 837 return size; 838 839 err = check_ptr_alignment(reg, off, size); 840 if (err) 841 return err; 842 843 if (reg->type == PTR_TO_MAP_VALUE || 844 reg->type == PTR_TO_MAP_VALUE_ADJ) { 845 if (t == BPF_WRITE && value_regno >= 0 && 846 is_pointer_value(env, value_regno)) { 847 verbose("R%d leaks addr into map\n", value_regno); 848 return -EACCES; 849 } 850 851 if (reg->type == PTR_TO_MAP_VALUE_ADJ) 852 err = check_map_access_adj(env, regno, off, size); 853 else 854 err = check_map_access(env, regno, off, size); 855 if (!err && t == BPF_READ && value_regno >= 0) 856 mark_reg_unknown_value_and_range(state->regs, 857 value_regno); 858 859 } else if (reg->type == PTR_TO_CTX) { 860 enum bpf_reg_type reg_type = UNKNOWN_VALUE; 861 862 if (t == BPF_WRITE && value_regno >= 0 && 863 is_pointer_value(env, value_regno)) { 864 verbose("R%d leaks addr into ctx\n", value_regno); 865 return -EACCES; 866 } 867 err = check_ctx_access(env, off, size, t, ®_type); 868 if (!err && t == BPF_READ && value_regno >= 0) { 869 mark_reg_unknown_value_and_range(state->regs, 870 value_regno); 871 /* note that reg.[id|off|range] == 0 */ 872 state->regs[value_regno].type = reg_type; 873 } 874 875 } else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) { 876 if (off >= 0 || off < -MAX_BPF_STACK) { 877 verbose("invalid stack off=%d size=%d\n", off, size); 878 return -EACCES; 879 } 880 if (t == BPF_WRITE) { 881 if (!env->allow_ptr_leaks && 882 state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL && 883 size != BPF_REG_SIZE) { 884 verbose("attempt to corrupt spilled pointer on stack\n"); 885 return -EACCES; 886 } 887 err = check_stack_write(state, off, size, value_regno); 888 } else { 889 err = check_stack_read(state, off, size, value_regno); 890 } 891 } else if (state->regs[regno].type == PTR_TO_PACKET) { 892 if (t == BPF_WRITE && !may_access_direct_pkt_data(env, NULL, t)) { 893 verbose("cannot write into packet\n"); 894 return -EACCES; 895 } 896 if (t == BPF_WRITE && value_regno >= 0 && 897 is_pointer_value(env, value_regno)) { 898 verbose("R%d leaks addr into packet\n", value_regno); 899 return -EACCES; 900 } 901 err = check_packet_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 } else { 906 verbose("R%d invalid mem access '%s'\n", 907 regno, reg_type_str[reg->type]); 908 return -EACCES; 909 } 910 911 if (!err && size <= 2 && value_regno >= 0 && env->allow_ptr_leaks && 912 state->regs[value_regno].type == UNKNOWN_VALUE) { 913 /* 1 or 2 byte load zero-extends, determine the number of 914 * zero upper bits. Not doing it fo 4 byte load, since 915 * such values cannot be added to ptr_to_packet anyway. 916 */ 917 state->regs[value_regno].imm = 64 - size * 8; 918 } 919 return err; 920 } 921 922 static int check_xadd(struct bpf_verifier_env *env, struct bpf_insn *insn) 923 { 924 struct bpf_reg_state *regs = env->cur_state.regs; 925 int err; 926 927 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) || 928 insn->imm != 0) { 929 verbose("BPF_XADD uses reserved fields\n"); 930 return -EINVAL; 931 } 932 933 /* check src1 operand */ 934 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 935 if (err) 936 return err; 937 938 /* check src2 operand */ 939 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 940 if (err) 941 return err; 942 943 /* check whether atomic_add can read the memory */ 944 err = check_mem_access(env, insn->dst_reg, insn->off, 945 BPF_SIZE(insn->code), BPF_READ, -1); 946 if (err) 947 return err; 948 949 /* check whether atomic_add can write into the same memory */ 950 return check_mem_access(env, insn->dst_reg, insn->off, 951 BPF_SIZE(insn->code), BPF_WRITE, -1); 952 } 953 954 /* when register 'regno' is passed into function that will read 'access_size' 955 * bytes from that pointer, make sure that it's within stack boundary 956 * and all elements of stack are initialized 957 */ 958 static int check_stack_boundary(struct bpf_verifier_env *env, int regno, 959 int access_size, bool zero_size_allowed, 960 struct bpf_call_arg_meta *meta) 961 { 962 struct bpf_verifier_state *state = &env->cur_state; 963 struct bpf_reg_state *regs = state->regs; 964 int off, i; 965 966 if (regs[regno].type != PTR_TO_STACK) { 967 if (zero_size_allowed && access_size == 0 && 968 regs[regno].type == CONST_IMM && 969 regs[regno].imm == 0) 970 return 0; 971 972 verbose("R%d type=%s expected=%s\n", regno, 973 reg_type_str[regs[regno].type], 974 reg_type_str[PTR_TO_STACK]); 975 return -EACCES; 976 } 977 978 off = regs[regno].imm; 979 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 || 980 access_size <= 0) { 981 verbose("invalid stack type R%d off=%d access_size=%d\n", 982 regno, off, access_size); 983 return -EACCES; 984 } 985 986 if (meta && meta->raw_mode) { 987 meta->access_size = access_size; 988 meta->regno = regno; 989 return 0; 990 } 991 992 for (i = 0; i < access_size; i++) { 993 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) { 994 verbose("invalid indirect read from stack off %d+%d size %d\n", 995 off, i, access_size); 996 return -EACCES; 997 } 998 } 999 return 0; 1000 } 1001 1002 static int check_helper_mem_access(struct bpf_verifier_env *env, int regno, 1003 int access_size, bool zero_size_allowed, 1004 struct bpf_call_arg_meta *meta) 1005 { 1006 struct bpf_reg_state *regs = env->cur_state.regs; 1007 1008 switch (regs[regno].type) { 1009 case PTR_TO_PACKET: 1010 return check_packet_access(env, regno, 0, access_size); 1011 case PTR_TO_MAP_VALUE: 1012 return check_map_access(env, regno, 0, access_size); 1013 case PTR_TO_MAP_VALUE_ADJ: 1014 return check_map_access_adj(env, regno, 0, access_size); 1015 default: /* const_imm|ptr_to_stack or invalid ptr */ 1016 return check_stack_boundary(env, regno, access_size, 1017 zero_size_allowed, meta); 1018 } 1019 } 1020 1021 static int check_func_arg(struct bpf_verifier_env *env, u32 regno, 1022 enum bpf_arg_type arg_type, 1023 struct bpf_call_arg_meta *meta) 1024 { 1025 struct bpf_reg_state *regs = env->cur_state.regs, *reg = ®s[regno]; 1026 enum bpf_reg_type expected_type, type = reg->type; 1027 int err = 0; 1028 1029 if (arg_type == ARG_DONTCARE) 1030 return 0; 1031 1032 if (type == NOT_INIT) { 1033 verbose("R%d !read_ok\n", regno); 1034 return -EACCES; 1035 } 1036 1037 if (arg_type == ARG_ANYTHING) { 1038 if (is_pointer_value(env, regno)) { 1039 verbose("R%d leaks addr into helper function\n", regno); 1040 return -EACCES; 1041 } 1042 return 0; 1043 } 1044 1045 if (type == PTR_TO_PACKET && 1046 !may_access_direct_pkt_data(env, meta, BPF_READ)) { 1047 verbose("helper access to the packet is not allowed\n"); 1048 return -EACCES; 1049 } 1050 1051 if (arg_type == ARG_PTR_TO_MAP_KEY || 1052 arg_type == ARG_PTR_TO_MAP_VALUE) { 1053 expected_type = PTR_TO_STACK; 1054 if (type != PTR_TO_PACKET && type != expected_type) 1055 goto err_type; 1056 } else if (arg_type == ARG_CONST_SIZE || 1057 arg_type == ARG_CONST_SIZE_OR_ZERO) { 1058 expected_type = CONST_IMM; 1059 /* One exception. Allow UNKNOWN_VALUE registers when the 1060 * boundaries are known and don't cause unsafe memory accesses 1061 */ 1062 if (type != UNKNOWN_VALUE && type != expected_type) 1063 goto err_type; 1064 } else if (arg_type == ARG_CONST_MAP_PTR) { 1065 expected_type = CONST_PTR_TO_MAP; 1066 if (type != expected_type) 1067 goto err_type; 1068 } else if (arg_type == ARG_PTR_TO_CTX) { 1069 expected_type = PTR_TO_CTX; 1070 if (type != expected_type) 1071 goto err_type; 1072 } else if (arg_type == ARG_PTR_TO_MEM || 1073 arg_type == ARG_PTR_TO_UNINIT_MEM) { 1074 expected_type = PTR_TO_STACK; 1075 /* One exception here. In case function allows for NULL to be 1076 * passed in as argument, it's a CONST_IMM type. Final test 1077 * happens during stack boundary checking. 1078 */ 1079 if (type == CONST_IMM && reg->imm == 0) 1080 /* final test in check_stack_boundary() */; 1081 else if (type != PTR_TO_PACKET && type != PTR_TO_MAP_VALUE && 1082 type != PTR_TO_MAP_VALUE_ADJ && type != expected_type) 1083 goto err_type; 1084 meta->raw_mode = arg_type == ARG_PTR_TO_UNINIT_MEM; 1085 } else { 1086 verbose("unsupported arg_type %d\n", arg_type); 1087 return -EFAULT; 1088 } 1089 1090 if (arg_type == ARG_CONST_MAP_PTR) { 1091 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */ 1092 meta->map_ptr = reg->map_ptr; 1093 } else if (arg_type == ARG_PTR_TO_MAP_KEY) { 1094 /* bpf_map_xxx(..., map_ptr, ..., key) call: 1095 * check that [key, key + map->key_size) are within 1096 * stack limits and initialized 1097 */ 1098 if (!meta->map_ptr) { 1099 /* in function declaration map_ptr must come before 1100 * map_key, so that it's verified and known before 1101 * we have to check map_key here. Otherwise it means 1102 * that kernel subsystem misconfigured verifier 1103 */ 1104 verbose("invalid map_ptr to access map->key\n"); 1105 return -EACCES; 1106 } 1107 if (type == PTR_TO_PACKET) 1108 err = check_packet_access(env, regno, 0, 1109 meta->map_ptr->key_size); 1110 else 1111 err = check_stack_boundary(env, regno, 1112 meta->map_ptr->key_size, 1113 false, NULL); 1114 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) { 1115 /* bpf_map_xxx(..., map_ptr, ..., value) call: 1116 * check [value, value + map->value_size) validity 1117 */ 1118 if (!meta->map_ptr) { 1119 /* kernel subsystem misconfigured verifier */ 1120 verbose("invalid map_ptr to access map->value\n"); 1121 return -EACCES; 1122 } 1123 if (type == PTR_TO_PACKET) 1124 err = check_packet_access(env, regno, 0, 1125 meta->map_ptr->value_size); 1126 else 1127 err = check_stack_boundary(env, regno, 1128 meta->map_ptr->value_size, 1129 false, NULL); 1130 } else if (arg_type == ARG_CONST_SIZE || 1131 arg_type == ARG_CONST_SIZE_OR_ZERO) { 1132 bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO); 1133 1134 /* bpf_xxx(..., buf, len) call will access 'len' bytes 1135 * from stack pointer 'buf'. Check it 1136 * note: regno == len, regno - 1 == buf 1137 */ 1138 if (regno == 0) { 1139 /* kernel subsystem misconfigured verifier */ 1140 verbose("ARG_CONST_SIZE cannot be first argument\n"); 1141 return -EACCES; 1142 } 1143 1144 /* If the register is UNKNOWN_VALUE, the access check happens 1145 * using its boundaries. Otherwise, just use its imm 1146 */ 1147 if (type == UNKNOWN_VALUE) { 1148 /* For unprivileged variable accesses, disable raw 1149 * mode so that the program is required to 1150 * initialize all the memory that the helper could 1151 * just partially fill up. 1152 */ 1153 meta = NULL; 1154 1155 if (reg->min_value < 0) { 1156 verbose("R%d min value is negative, either use unsigned or 'var &= const'\n", 1157 regno); 1158 return -EACCES; 1159 } 1160 1161 if (reg->min_value == 0) { 1162 err = check_helper_mem_access(env, regno - 1, 0, 1163 zero_size_allowed, 1164 meta); 1165 if (err) 1166 return err; 1167 } 1168 1169 if (reg->max_value == BPF_REGISTER_MAX_RANGE) { 1170 verbose("R%d unbounded memory access, use 'var &= const' or 'if (var < const)'\n", 1171 regno); 1172 return -EACCES; 1173 } 1174 err = check_helper_mem_access(env, regno - 1, 1175 reg->max_value, 1176 zero_size_allowed, meta); 1177 if (err) 1178 return err; 1179 } else { 1180 /* register is CONST_IMM */ 1181 err = check_helper_mem_access(env, regno - 1, reg->imm, 1182 zero_size_allowed, meta); 1183 } 1184 } 1185 1186 return err; 1187 err_type: 1188 verbose("R%d type=%s expected=%s\n", regno, 1189 reg_type_str[type], reg_type_str[expected_type]); 1190 return -EACCES; 1191 } 1192 1193 static int check_map_func_compatibility(struct bpf_map *map, int func_id) 1194 { 1195 if (!map) 1196 return 0; 1197 1198 /* We need a two way check, first is from map perspective ... */ 1199 switch (map->map_type) { 1200 case BPF_MAP_TYPE_PROG_ARRAY: 1201 if (func_id != BPF_FUNC_tail_call) 1202 goto error; 1203 break; 1204 case BPF_MAP_TYPE_PERF_EVENT_ARRAY: 1205 if (func_id != BPF_FUNC_perf_event_read && 1206 func_id != BPF_FUNC_perf_event_output) 1207 goto error; 1208 break; 1209 case BPF_MAP_TYPE_STACK_TRACE: 1210 if (func_id != BPF_FUNC_get_stackid) 1211 goto error; 1212 break; 1213 case BPF_MAP_TYPE_CGROUP_ARRAY: 1214 if (func_id != BPF_FUNC_skb_under_cgroup && 1215 func_id != BPF_FUNC_current_task_under_cgroup) 1216 goto error; 1217 break; 1218 default: 1219 break; 1220 } 1221 1222 /* ... and second from the function itself. */ 1223 switch (func_id) { 1224 case BPF_FUNC_tail_call: 1225 if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY) 1226 goto error; 1227 break; 1228 case BPF_FUNC_perf_event_read: 1229 case BPF_FUNC_perf_event_output: 1230 if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY) 1231 goto error; 1232 break; 1233 case BPF_FUNC_get_stackid: 1234 if (map->map_type != BPF_MAP_TYPE_STACK_TRACE) 1235 goto error; 1236 break; 1237 case BPF_FUNC_current_task_under_cgroup: 1238 case BPF_FUNC_skb_under_cgroup: 1239 if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY) 1240 goto error; 1241 break; 1242 default: 1243 break; 1244 } 1245 1246 return 0; 1247 error: 1248 verbose("cannot pass map_type %d into func %s#%d\n", 1249 map->map_type, func_id_name(func_id), func_id); 1250 return -EINVAL; 1251 } 1252 1253 static int check_raw_mode(const struct bpf_func_proto *fn) 1254 { 1255 int count = 0; 1256 1257 if (fn->arg1_type == ARG_PTR_TO_UNINIT_MEM) 1258 count++; 1259 if (fn->arg2_type == ARG_PTR_TO_UNINIT_MEM) 1260 count++; 1261 if (fn->arg3_type == ARG_PTR_TO_UNINIT_MEM) 1262 count++; 1263 if (fn->arg4_type == ARG_PTR_TO_UNINIT_MEM) 1264 count++; 1265 if (fn->arg5_type == ARG_PTR_TO_UNINIT_MEM) 1266 count++; 1267 1268 return count > 1 ? -EINVAL : 0; 1269 } 1270 1271 static void clear_all_pkt_pointers(struct bpf_verifier_env *env) 1272 { 1273 struct bpf_verifier_state *state = &env->cur_state; 1274 struct bpf_reg_state *regs = state->regs, *reg; 1275 int i; 1276 1277 for (i = 0; i < MAX_BPF_REG; i++) 1278 if (regs[i].type == PTR_TO_PACKET || 1279 regs[i].type == PTR_TO_PACKET_END) 1280 mark_reg_unknown_value(regs, i); 1281 1282 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 1283 if (state->stack_slot_type[i] != STACK_SPILL) 1284 continue; 1285 reg = &state->spilled_regs[i / BPF_REG_SIZE]; 1286 if (reg->type != PTR_TO_PACKET && 1287 reg->type != PTR_TO_PACKET_END) 1288 continue; 1289 reg->type = UNKNOWN_VALUE; 1290 reg->imm = 0; 1291 } 1292 } 1293 1294 static int check_call(struct bpf_verifier_env *env, int func_id) 1295 { 1296 struct bpf_verifier_state *state = &env->cur_state; 1297 const struct bpf_func_proto *fn = NULL; 1298 struct bpf_reg_state *regs = state->regs; 1299 struct bpf_reg_state *reg; 1300 struct bpf_call_arg_meta meta; 1301 bool changes_data; 1302 int i, err; 1303 1304 /* find function prototype */ 1305 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) { 1306 verbose("invalid func %s#%d\n", func_id_name(func_id), func_id); 1307 return -EINVAL; 1308 } 1309 1310 if (env->prog->aux->ops->get_func_proto) 1311 fn = env->prog->aux->ops->get_func_proto(func_id); 1312 1313 if (!fn) { 1314 verbose("unknown func %s#%d\n", func_id_name(func_id), func_id); 1315 return -EINVAL; 1316 } 1317 1318 /* eBPF programs must be GPL compatible to use GPL-ed functions */ 1319 if (!env->prog->gpl_compatible && fn->gpl_only) { 1320 verbose("cannot call GPL only function from proprietary program\n"); 1321 return -EINVAL; 1322 } 1323 1324 changes_data = bpf_helper_changes_pkt_data(fn->func); 1325 1326 memset(&meta, 0, sizeof(meta)); 1327 meta.pkt_access = fn->pkt_access; 1328 1329 /* We only support one arg being in raw mode at the moment, which 1330 * is sufficient for the helper functions we have right now. 1331 */ 1332 err = check_raw_mode(fn); 1333 if (err) { 1334 verbose("kernel subsystem misconfigured func %s#%d\n", 1335 func_id_name(func_id), func_id); 1336 return err; 1337 } 1338 1339 /* check args */ 1340 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta); 1341 if (err) 1342 return err; 1343 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta); 1344 if (err) 1345 return err; 1346 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta); 1347 if (err) 1348 return err; 1349 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta); 1350 if (err) 1351 return err; 1352 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta); 1353 if (err) 1354 return err; 1355 1356 /* Mark slots with STACK_MISC in case of raw mode, stack offset 1357 * is inferred from register state. 1358 */ 1359 for (i = 0; i < meta.access_size; i++) { 1360 err = check_mem_access(env, meta.regno, i, BPF_B, BPF_WRITE, -1); 1361 if (err) 1362 return err; 1363 } 1364 1365 /* reset caller saved regs */ 1366 for (i = 0; i < CALLER_SAVED_REGS; i++) { 1367 reg = regs + caller_saved[i]; 1368 reg->type = NOT_INIT; 1369 reg->imm = 0; 1370 } 1371 1372 /* update return register */ 1373 if (fn->ret_type == RET_INTEGER) { 1374 regs[BPF_REG_0].type = UNKNOWN_VALUE; 1375 } else if (fn->ret_type == RET_VOID) { 1376 regs[BPF_REG_0].type = NOT_INIT; 1377 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) { 1378 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL; 1379 regs[BPF_REG_0].max_value = regs[BPF_REG_0].min_value = 0; 1380 /* remember map_ptr, so that check_map_access() 1381 * can check 'value_size' boundary of memory access 1382 * to map element returned from bpf_map_lookup_elem() 1383 */ 1384 if (meta.map_ptr == NULL) { 1385 verbose("kernel subsystem misconfigured verifier\n"); 1386 return -EINVAL; 1387 } 1388 regs[BPF_REG_0].map_ptr = meta.map_ptr; 1389 regs[BPF_REG_0].id = ++env->id_gen; 1390 } else { 1391 verbose("unknown return type %d of func %s#%d\n", 1392 fn->ret_type, func_id_name(func_id), func_id); 1393 return -EINVAL; 1394 } 1395 1396 err = check_map_func_compatibility(meta.map_ptr, func_id); 1397 if (err) 1398 return err; 1399 1400 if (changes_data) 1401 clear_all_pkt_pointers(env); 1402 return 0; 1403 } 1404 1405 static int check_packet_ptr_add(struct bpf_verifier_env *env, 1406 struct bpf_insn *insn) 1407 { 1408 struct bpf_reg_state *regs = env->cur_state.regs; 1409 struct bpf_reg_state *dst_reg = ®s[insn->dst_reg]; 1410 struct bpf_reg_state *src_reg = ®s[insn->src_reg]; 1411 struct bpf_reg_state tmp_reg; 1412 s32 imm; 1413 1414 if (BPF_SRC(insn->code) == BPF_K) { 1415 /* pkt_ptr += imm */ 1416 imm = insn->imm; 1417 1418 add_imm: 1419 if (imm < 0) { 1420 verbose("addition of negative constant to packet pointer is not allowed\n"); 1421 return -EACCES; 1422 } 1423 if (imm >= MAX_PACKET_OFF || 1424 imm + dst_reg->off >= MAX_PACKET_OFF) { 1425 verbose("constant %d is too large to add to packet pointer\n", 1426 imm); 1427 return -EACCES; 1428 } 1429 /* a constant was added to pkt_ptr. 1430 * Remember it while keeping the same 'id' 1431 */ 1432 dst_reg->off += imm; 1433 } else { 1434 if (src_reg->type == PTR_TO_PACKET) { 1435 /* R6=pkt(id=0,off=0,r=62) R7=imm22; r7 += r6 */ 1436 tmp_reg = *dst_reg; /* save r7 state */ 1437 *dst_reg = *src_reg; /* copy pkt_ptr state r6 into r7 */ 1438 src_reg = &tmp_reg; /* pretend it's src_reg state */ 1439 /* if the checks below reject it, the copy won't matter, 1440 * since we're rejecting the whole program. If all ok, 1441 * then imm22 state will be added to r7 1442 * and r7 will be pkt(id=0,off=22,r=62) while 1443 * r6 will stay as pkt(id=0,off=0,r=62) 1444 */ 1445 } 1446 1447 if (src_reg->type == CONST_IMM) { 1448 /* pkt_ptr += reg where reg is known constant */ 1449 imm = src_reg->imm; 1450 goto add_imm; 1451 } 1452 /* disallow pkt_ptr += reg 1453 * if reg is not uknown_value with guaranteed zero upper bits 1454 * otherwise pkt_ptr may overflow and addition will become 1455 * subtraction which is not allowed 1456 */ 1457 if (src_reg->type != UNKNOWN_VALUE) { 1458 verbose("cannot add '%s' to ptr_to_packet\n", 1459 reg_type_str[src_reg->type]); 1460 return -EACCES; 1461 } 1462 if (src_reg->imm < 48) { 1463 verbose("cannot add integer value with %lld upper zero bits to ptr_to_packet\n", 1464 src_reg->imm); 1465 return -EACCES; 1466 } 1467 /* dst_reg stays as pkt_ptr type and since some positive 1468 * integer value was added to the pointer, increment its 'id' 1469 */ 1470 dst_reg->id = ++env->id_gen; 1471 1472 /* something was added to pkt_ptr, set range and off to zero */ 1473 dst_reg->off = 0; 1474 dst_reg->range = 0; 1475 } 1476 return 0; 1477 } 1478 1479 static int evaluate_reg_alu(struct bpf_verifier_env *env, struct bpf_insn *insn) 1480 { 1481 struct bpf_reg_state *regs = env->cur_state.regs; 1482 struct bpf_reg_state *dst_reg = ®s[insn->dst_reg]; 1483 u8 opcode = BPF_OP(insn->code); 1484 s64 imm_log2; 1485 1486 /* for type == UNKNOWN_VALUE: 1487 * imm > 0 -> number of zero upper bits 1488 * imm == 0 -> don't track which is the same as all bits can be non-zero 1489 */ 1490 1491 if (BPF_SRC(insn->code) == BPF_X) { 1492 struct bpf_reg_state *src_reg = ®s[insn->src_reg]; 1493 1494 if (src_reg->type == UNKNOWN_VALUE && src_reg->imm > 0 && 1495 dst_reg->imm && opcode == BPF_ADD) { 1496 /* dreg += sreg 1497 * where both have zero upper bits. Adding them 1498 * can only result making one more bit non-zero 1499 * in the larger value. 1500 * Ex. 0xffff (imm=48) + 1 (imm=63) = 0x10000 (imm=47) 1501 * 0xffff (imm=48) + 0xffff = 0x1fffe (imm=47) 1502 */ 1503 dst_reg->imm = min(dst_reg->imm, src_reg->imm); 1504 dst_reg->imm--; 1505 return 0; 1506 } 1507 if (src_reg->type == CONST_IMM && src_reg->imm > 0 && 1508 dst_reg->imm && opcode == BPF_ADD) { 1509 /* dreg += sreg 1510 * where dreg has zero upper bits and sreg is const. 1511 * Adding them can only result making one more bit 1512 * non-zero in the larger value. 1513 */ 1514 imm_log2 = __ilog2_u64((long long)src_reg->imm); 1515 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2); 1516 dst_reg->imm--; 1517 return 0; 1518 } 1519 /* all other cases non supported yet, just mark dst_reg */ 1520 dst_reg->imm = 0; 1521 return 0; 1522 } 1523 1524 /* sign extend 32-bit imm into 64-bit to make sure that 1525 * negative values occupy bit 63. Note ilog2() would have 1526 * been incorrect, since sizeof(insn->imm) == 4 1527 */ 1528 imm_log2 = __ilog2_u64((long long)insn->imm); 1529 1530 if (dst_reg->imm && opcode == BPF_LSH) { 1531 /* reg <<= imm 1532 * if reg was a result of 2 byte load, then its imm == 48 1533 * which means that upper 48 bits are zero and shifting this reg 1534 * left by 4 would mean that upper 44 bits are still zero 1535 */ 1536 dst_reg->imm -= insn->imm; 1537 } else if (dst_reg->imm && opcode == BPF_MUL) { 1538 /* reg *= imm 1539 * if multiplying by 14 subtract 4 1540 * This is conservative calculation of upper zero bits. 1541 * It's not trying to special case insn->imm == 1 or 0 cases 1542 */ 1543 dst_reg->imm -= imm_log2 + 1; 1544 } else if (opcode == BPF_AND) { 1545 /* reg &= imm */ 1546 dst_reg->imm = 63 - imm_log2; 1547 } else if (dst_reg->imm && opcode == BPF_ADD) { 1548 /* reg += imm */ 1549 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2); 1550 dst_reg->imm--; 1551 } else if (opcode == BPF_RSH) { 1552 /* reg >>= imm 1553 * which means that after right shift, upper bits will be zero 1554 * note that verifier already checked that 1555 * 0 <= imm < 64 for shift insn 1556 */ 1557 dst_reg->imm += insn->imm; 1558 if (unlikely(dst_reg->imm > 64)) 1559 /* some dumb code did: 1560 * r2 = *(u32 *)mem; 1561 * r2 >>= 32; 1562 * and all bits are zero now */ 1563 dst_reg->imm = 64; 1564 } else { 1565 /* all other alu ops, means that we don't know what will 1566 * happen to the value, mark it with unknown number of zero bits 1567 */ 1568 dst_reg->imm = 0; 1569 } 1570 1571 if (dst_reg->imm < 0) { 1572 /* all 64 bits of the register can contain non-zero bits 1573 * and such value cannot be added to ptr_to_packet, since it 1574 * may overflow, mark it as unknown to avoid further eval 1575 */ 1576 dst_reg->imm = 0; 1577 } 1578 return 0; 1579 } 1580 1581 static int evaluate_reg_imm_alu(struct bpf_verifier_env *env, 1582 struct bpf_insn *insn) 1583 { 1584 struct bpf_reg_state *regs = env->cur_state.regs; 1585 struct bpf_reg_state *dst_reg = ®s[insn->dst_reg]; 1586 struct bpf_reg_state *src_reg = ®s[insn->src_reg]; 1587 u8 opcode = BPF_OP(insn->code); 1588 u64 dst_imm = dst_reg->imm; 1589 1590 /* dst_reg->type == CONST_IMM here. Simulate execution of insns 1591 * containing ALU ops. Don't care about overflow or negative 1592 * values, just add/sub/... them; registers are in u64. 1593 */ 1594 if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_K) { 1595 dst_imm += insn->imm; 1596 } else if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_X && 1597 src_reg->type == CONST_IMM) { 1598 dst_imm += src_reg->imm; 1599 } else if (opcode == BPF_SUB && BPF_SRC(insn->code) == BPF_K) { 1600 dst_imm -= insn->imm; 1601 } else if (opcode == BPF_SUB && BPF_SRC(insn->code) == BPF_X && 1602 src_reg->type == CONST_IMM) { 1603 dst_imm -= src_reg->imm; 1604 } else if (opcode == BPF_MUL && BPF_SRC(insn->code) == BPF_K) { 1605 dst_imm *= insn->imm; 1606 } else if (opcode == BPF_MUL && BPF_SRC(insn->code) == BPF_X && 1607 src_reg->type == CONST_IMM) { 1608 dst_imm *= src_reg->imm; 1609 } else if (opcode == BPF_OR && BPF_SRC(insn->code) == BPF_K) { 1610 dst_imm |= insn->imm; 1611 } else if (opcode == BPF_OR && BPF_SRC(insn->code) == BPF_X && 1612 src_reg->type == CONST_IMM) { 1613 dst_imm |= src_reg->imm; 1614 } else if (opcode == BPF_AND && BPF_SRC(insn->code) == BPF_K) { 1615 dst_imm &= insn->imm; 1616 } else if (opcode == BPF_AND && BPF_SRC(insn->code) == BPF_X && 1617 src_reg->type == CONST_IMM) { 1618 dst_imm &= src_reg->imm; 1619 } else if (opcode == BPF_RSH && BPF_SRC(insn->code) == BPF_K) { 1620 dst_imm >>= insn->imm; 1621 } else if (opcode == BPF_RSH && BPF_SRC(insn->code) == BPF_X && 1622 src_reg->type == CONST_IMM) { 1623 dst_imm >>= src_reg->imm; 1624 } else if (opcode == BPF_LSH && BPF_SRC(insn->code) == BPF_K) { 1625 dst_imm <<= insn->imm; 1626 } else if (opcode == BPF_LSH && BPF_SRC(insn->code) == BPF_X && 1627 src_reg->type == CONST_IMM) { 1628 dst_imm <<= src_reg->imm; 1629 } else { 1630 mark_reg_unknown_value(regs, insn->dst_reg); 1631 goto out; 1632 } 1633 1634 dst_reg->imm = dst_imm; 1635 out: 1636 return 0; 1637 } 1638 1639 static void check_reg_overflow(struct bpf_reg_state *reg) 1640 { 1641 if (reg->max_value > BPF_REGISTER_MAX_RANGE) 1642 reg->max_value = BPF_REGISTER_MAX_RANGE; 1643 if (reg->min_value < BPF_REGISTER_MIN_RANGE || 1644 reg->min_value > BPF_REGISTER_MAX_RANGE) 1645 reg->min_value = BPF_REGISTER_MIN_RANGE; 1646 } 1647 1648 static void adjust_reg_min_max_vals(struct bpf_verifier_env *env, 1649 struct bpf_insn *insn) 1650 { 1651 struct bpf_reg_state *regs = env->cur_state.regs, *dst_reg; 1652 s64 min_val = BPF_REGISTER_MIN_RANGE; 1653 u64 max_val = BPF_REGISTER_MAX_RANGE; 1654 u8 opcode = BPF_OP(insn->code); 1655 1656 dst_reg = ®s[insn->dst_reg]; 1657 if (BPF_SRC(insn->code) == BPF_X) { 1658 check_reg_overflow(®s[insn->src_reg]); 1659 min_val = regs[insn->src_reg].min_value; 1660 max_val = regs[insn->src_reg].max_value; 1661 1662 /* If the source register is a random pointer then the 1663 * min_value/max_value values represent the range of the known 1664 * accesses into that value, not the actual min/max value of the 1665 * register itself. In this case we have to reset the reg range 1666 * values so we know it is not safe to look at. 1667 */ 1668 if (regs[insn->src_reg].type != CONST_IMM && 1669 regs[insn->src_reg].type != UNKNOWN_VALUE) { 1670 min_val = BPF_REGISTER_MIN_RANGE; 1671 max_val = BPF_REGISTER_MAX_RANGE; 1672 } 1673 } else if (insn->imm < BPF_REGISTER_MAX_RANGE && 1674 (s64)insn->imm > BPF_REGISTER_MIN_RANGE) { 1675 min_val = max_val = insn->imm; 1676 } 1677 1678 /* We don't know anything about what was done to this register, mark it 1679 * as unknown. 1680 */ 1681 if (min_val == BPF_REGISTER_MIN_RANGE && 1682 max_val == BPF_REGISTER_MAX_RANGE) { 1683 reset_reg_range_values(regs, insn->dst_reg); 1684 return; 1685 } 1686 1687 /* If one of our values was at the end of our ranges then we can't just 1688 * do our normal operations to the register, we need to set the values 1689 * to the min/max since they are undefined. 1690 */ 1691 if (min_val == BPF_REGISTER_MIN_RANGE) 1692 dst_reg->min_value = BPF_REGISTER_MIN_RANGE; 1693 if (max_val == BPF_REGISTER_MAX_RANGE) 1694 dst_reg->max_value = BPF_REGISTER_MAX_RANGE; 1695 1696 switch (opcode) { 1697 case BPF_ADD: 1698 if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) 1699 dst_reg->min_value += min_val; 1700 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1701 dst_reg->max_value += max_val; 1702 break; 1703 case BPF_SUB: 1704 if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) 1705 dst_reg->min_value -= min_val; 1706 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1707 dst_reg->max_value -= max_val; 1708 break; 1709 case BPF_MUL: 1710 if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) 1711 dst_reg->min_value *= min_val; 1712 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1713 dst_reg->max_value *= max_val; 1714 break; 1715 case BPF_AND: 1716 /* Disallow AND'ing of negative numbers, ain't nobody got time 1717 * for that. Otherwise the minimum is 0 and the max is the max 1718 * value we could AND against. 1719 */ 1720 if (min_val < 0) 1721 dst_reg->min_value = BPF_REGISTER_MIN_RANGE; 1722 else 1723 dst_reg->min_value = 0; 1724 dst_reg->max_value = max_val; 1725 break; 1726 case BPF_LSH: 1727 /* Gotta have special overflow logic here, if we're shifting 1728 * more than MAX_RANGE then just assume we have an invalid 1729 * range. 1730 */ 1731 if (min_val > ilog2(BPF_REGISTER_MAX_RANGE)) 1732 dst_reg->min_value = BPF_REGISTER_MIN_RANGE; 1733 else if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) 1734 dst_reg->min_value <<= min_val; 1735 1736 if (max_val > ilog2(BPF_REGISTER_MAX_RANGE)) 1737 dst_reg->max_value = BPF_REGISTER_MAX_RANGE; 1738 else if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1739 dst_reg->max_value <<= max_val; 1740 break; 1741 case BPF_RSH: 1742 /* RSH by a negative number is undefined, and the BPF_RSH is an 1743 * unsigned shift, so make the appropriate casts. 1744 */ 1745 if (min_val < 0 || dst_reg->min_value < 0) 1746 dst_reg->min_value = BPF_REGISTER_MIN_RANGE; 1747 else 1748 dst_reg->min_value = 1749 (u64)(dst_reg->min_value) >> min_val; 1750 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1751 dst_reg->max_value >>= max_val; 1752 break; 1753 default: 1754 reset_reg_range_values(regs, insn->dst_reg); 1755 break; 1756 } 1757 1758 check_reg_overflow(dst_reg); 1759 } 1760 1761 /* check validity of 32-bit and 64-bit arithmetic operations */ 1762 static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn) 1763 { 1764 struct bpf_reg_state *regs = env->cur_state.regs, *dst_reg; 1765 u8 opcode = BPF_OP(insn->code); 1766 int err; 1767 1768 if (opcode == BPF_END || opcode == BPF_NEG) { 1769 if (opcode == BPF_NEG) { 1770 if (BPF_SRC(insn->code) != 0 || 1771 insn->src_reg != BPF_REG_0 || 1772 insn->off != 0 || insn->imm != 0) { 1773 verbose("BPF_NEG uses reserved fields\n"); 1774 return -EINVAL; 1775 } 1776 } else { 1777 if (insn->src_reg != BPF_REG_0 || insn->off != 0 || 1778 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) { 1779 verbose("BPF_END uses reserved fields\n"); 1780 return -EINVAL; 1781 } 1782 } 1783 1784 /* check src operand */ 1785 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1786 if (err) 1787 return err; 1788 1789 if (is_pointer_value(env, insn->dst_reg)) { 1790 verbose("R%d pointer arithmetic prohibited\n", 1791 insn->dst_reg); 1792 return -EACCES; 1793 } 1794 1795 /* check dest operand */ 1796 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1797 if (err) 1798 return err; 1799 1800 } else if (opcode == BPF_MOV) { 1801 1802 if (BPF_SRC(insn->code) == BPF_X) { 1803 if (insn->imm != 0 || insn->off != 0) { 1804 verbose("BPF_MOV uses reserved fields\n"); 1805 return -EINVAL; 1806 } 1807 1808 /* check src operand */ 1809 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1810 if (err) 1811 return err; 1812 } else { 1813 if (insn->src_reg != BPF_REG_0 || insn->off != 0) { 1814 verbose("BPF_MOV uses reserved fields\n"); 1815 return -EINVAL; 1816 } 1817 } 1818 1819 /* check dest operand */ 1820 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1821 if (err) 1822 return err; 1823 1824 /* we are setting our register to something new, we need to 1825 * reset its range values. 1826 */ 1827 reset_reg_range_values(regs, insn->dst_reg); 1828 1829 if (BPF_SRC(insn->code) == BPF_X) { 1830 if (BPF_CLASS(insn->code) == BPF_ALU64) { 1831 /* case: R1 = R2 1832 * copy register state to dest reg 1833 */ 1834 regs[insn->dst_reg] = regs[insn->src_reg]; 1835 } else { 1836 if (is_pointer_value(env, insn->src_reg)) { 1837 verbose("R%d partial copy of pointer\n", 1838 insn->src_reg); 1839 return -EACCES; 1840 } 1841 mark_reg_unknown_value(regs, insn->dst_reg); 1842 } 1843 } else { 1844 /* case: R = imm 1845 * remember the value we stored into this reg 1846 */ 1847 regs[insn->dst_reg].type = CONST_IMM; 1848 regs[insn->dst_reg].imm = insn->imm; 1849 regs[insn->dst_reg].max_value = insn->imm; 1850 regs[insn->dst_reg].min_value = insn->imm; 1851 } 1852 1853 } else if (opcode > BPF_END) { 1854 verbose("invalid BPF_ALU opcode %x\n", opcode); 1855 return -EINVAL; 1856 1857 } else { /* all other ALU ops: and, sub, xor, add, ... */ 1858 1859 if (BPF_SRC(insn->code) == BPF_X) { 1860 if (insn->imm != 0 || insn->off != 0) { 1861 verbose("BPF_ALU uses reserved fields\n"); 1862 return -EINVAL; 1863 } 1864 /* check src1 operand */ 1865 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1866 if (err) 1867 return err; 1868 } else { 1869 if (insn->src_reg != BPF_REG_0 || insn->off != 0) { 1870 verbose("BPF_ALU uses reserved fields\n"); 1871 return -EINVAL; 1872 } 1873 } 1874 1875 /* check src2 operand */ 1876 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1877 if (err) 1878 return err; 1879 1880 if ((opcode == BPF_MOD || opcode == BPF_DIV) && 1881 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) { 1882 verbose("div by zero\n"); 1883 return -EINVAL; 1884 } 1885 1886 if ((opcode == BPF_LSH || opcode == BPF_RSH || 1887 opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) { 1888 int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32; 1889 1890 if (insn->imm < 0 || insn->imm >= size) { 1891 verbose("invalid shift %d\n", insn->imm); 1892 return -EINVAL; 1893 } 1894 } 1895 1896 /* check dest operand */ 1897 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); 1898 if (err) 1899 return err; 1900 1901 dst_reg = ®s[insn->dst_reg]; 1902 1903 /* first we want to adjust our ranges. */ 1904 adjust_reg_min_max_vals(env, insn); 1905 1906 /* pattern match 'bpf_add Rx, imm' instruction */ 1907 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 && 1908 dst_reg->type == FRAME_PTR && BPF_SRC(insn->code) == BPF_K) { 1909 dst_reg->type = PTR_TO_STACK; 1910 dst_reg->imm = insn->imm; 1911 return 0; 1912 } else if (opcode == BPF_ADD && 1913 BPF_CLASS(insn->code) == BPF_ALU64 && 1914 (dst_reg->type == PTR_TO_PACKET || 1915 (BPF_SRC(insn->code) == BPF_X && 1916 regs[insn->src_reg].type == PTR_TO_PACKET))) { 1917 /* ptr_to_packet += K|X */ 1918 return check_packet_ptr_add(env, insn); 1919 } else if (BPF_CLASS(insn->code) == BPF_ALU64 && 1920 dst_reg->type == UNKNOWN_VALUE && 1921 env->allow_ptr_leaks) { 1922 /* unknown += K|X */ 1923 return evaluate_reg_alu(env, insn); 1924 } else if (BPF_CLASS(insn->code) == BPF_ALU64 && 1925 dst_reg->type == CONST_IMM && 1926 env->allow_ptr_leaks) { 1927 /* reg_imm += K|X */ 1928 return evaluate_reg_imm_alu(env, insn); 1929 } else if (is_pointer_value(env, insn->dst_reg)) { 1930 verbose("R%d pointer arithmetic prohibited\n", 1931 insn->dst_reg); 1932 return -EACCES; 1933 } else if (BPF_SRC(insn->code) == BPF_X && 1934 is_pointer_value(env, insn->src_reg)) { 1935 verbose("R%d pointer arithmetic prohibited\n", 1936 insn->src_reg); 1937 return -EACCES; 1938 } 1939 1940 /* If we did pointer math on a map value then just set it to our 1941 * PTR_TO_MAP_VALUE_ADJ type so we can deal with any stores or 1942 * loads to this register appropriately, otherwise just mark the 1943 * register as unknown. 1944 */ 1945 if (env->allow_ptr_leaks && 1946 BPF_CLASS(insn->code) == BPF_ALU64 && opcode == BPF_ADD && 1947 (dst_reg->type == PTR_TO_MAP_VALUE || 1948 dst_reg->type == PTR_TO_MAP_VALUE_ADJ)) 1949 dst_reg->type = PTR_TO_MAP_VALUE_ADJ; 1950 else 1951 mark_reg_unknown_value(regs, insn->dst_reg); 1952 } 1953 1954 return 0; 1955 } 1956 1957 static void find_good_pkt_pointers(struct bpf_verifier_state *state, 1958 struct bpf_reg_state *dst_reg) 1959 { 1960 struct bpf_reg_state *regs = state->regs, *reg; 1961 int i; 1962 1963 /* LLVM can generate two kind of checks: 1964 * 1965 * Type 1: 1966 * 1967 * r2 = r3; 1968 * r2 += 8; 1969 * if (r2 > pkt_end) goto <handle exception> 1970 * <access okay> 1971 * 1972 * Where: 1973 * r2 == dst_reg, pkt_end == src_reg 1974 * r2=pkt(id=n,off=8,r=0) 1975 * r3=pkt(id=n,off=0,r=0) 1976 * 1977 * Type 2: 1978 * 1979 * r2 = r3; 1980 * r2 += 8; 1981 * if (pkt_end >= r2) goto <access okay> 1982 * <handle exception> 1983 * 1984 * Where: 1985 * pkt_end == dst_reg, r2 == src_reg 1986 * r2=pkt(id=n,off=8,r=0) 1987 * r3=pkt(id=n,off=0,r=0) 1988 * 1989 * Find register r3 and mark its range as r3=pkt(id=n,off=0,r=8) 1990 * so that range of bytes [r3, r3 + 8) is safe to access. 1991 */ 1992 1993 for (i = 0; i < MAX_BPF_REG; i++) 1994 if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id) 1995 /* keep the maximum range already checked */ 1996 regs[i].range = max(regs[i].range, dst_reg->off); 1997 1998 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 1999 if (state->stack_slot_type[i] != STACK_SPILL) 2000 continue; 2001 reg = &state->spilled_regs[i / BPF_REG_SIZE]; 2002 if (reg->type == PTR_TO_PACKET && reg->id == dst_reg->id) 2003 reg->range = max(reg->range, dst_reg->off); 2004 } 2005 } 2006 2007 /* Adjusts the register min/max values in the case that the dst_reg is the 2008 * variable register that we are working on, and src_reg is a constant or we're 2009 * simply doing a BPF_K check. 2010 */ 2011 static void reg_set_min_max(struct bpf_reg_state *true_reg, 2012 struct bpf_reg_state *false_reg, u64 val, 2013 u8 opcode) 2014 { 2015 switch (opcode) { 2016 case BPF_JEQ: 2017 /* If this is false then we know nothing Jon Snow, but if it is 2018 * true then we know for sure. 2019 */ 2020 true_reg->max_value = true_reg->min_value = val; 2021 break; 2022 case BPF_JNE: 2023 /* If this is true we know nothing Jon Snow, but if it is false 2024 * we know the value for sure; 2025 */ 2026 false_reg->max_value = false_reg->min_value = val; 2027 break; 2028 case BPF_JGT: 2029 /* Unsigned comparison, the minimum value is 0. */ 2030 false_reg->min_value = 0; 2031 /* fallthrough */ 2032 case BPF_JSGT: 2033 /* If this is false then we know the maximum val is val, 2034 * otherwise we know the min val is val+1. 2035 */ 2036 false_reg->max_value = val; 2037 true_reg->min_value = val + 1; 2038 break; 2039 case BPF_JGE: 2040 /* Unsigned comparison, the minimum value is 0. */ 2041 false_reg->min_value = 0; 2042 /* fallthrough */ 2043 case BPF_JSGE: 2044 /* If this is false then we know the maximum value is val - 1, 2045 * otherwise we know the mimimum value is val. 2046 */ 2047 false_reg->max_value = val - 1; 2048 true_reg->min_value = val; 2049 break; 2050 default: 2051 break; 2052 } 2053 2054 check_reg_overflow(false_reg); 2055 check_reg_overflow(true_reg); 2056 } 2057 2058 /* Same as above, but for the case that dst_reg is a CONST_IMM reg and src_reg 2059 * is the variable reg. 2060 */ 2061 static void reg_set_min_max_inv(struct bpf_reg_state *true_reg, 2062 struct bpf_reg_state *false_reg, u64 val, 2063 u8 opcode) 2064 { 2065 switch (opcode) { 2066 case BPF_JEQ: 2067 /* If this is false then we know nothing Jon Snow, but if it is 2068 * true then we know for sure. 2069 */ 2070 true_reg->max_value = true_reg->min_value = val; 2071 break; 2072 case BPF_JNE: 2073 /* If this is true we know nothing Jon Snow, but if it is false 2074 * we know the value for sure; 2075 */ 2076 false_reg->max_value = false_reg->min_value = val; 2077 break; 2078 case BPF_JGT: 2079 /* Unsigned comparison, the minimum value is 0. */ 2080 true_reg->min_value = 0; 2081 /* fallthrough */ 2082 case BPF_JSGT: 2083 /* 2084 * If this is false, then the val is <= the register, if it is 2085 * true the register <= to the val. 2086 */ 2087 false_reg->min_value = val; 2088 true_reg->max_value = val - 1; 2089 break; 2090 case BPF_JGE: 2091 /* Unsigned comparison, the minimum value is 0. */ 2092 true_reg->min_value = 0; 2093 /* fallthrough */ 2094 case BPF_JSGE: 2095 /* If this is false then constant < register, if it is true then 2096 * the register < constant. 2097 */ 2098 false_reg->min_value = val + 1; 2099 true_reg->max_value = val; 2100 break; 2101 default: 2102 break; 2103 } 2104 2105 check_reg_overflow(false_reg); 2106 check_reg_overflow(true_reg); 2107 } 2108 2109 static void mark_map_reg(struct bpf_reg_state *regs, u32 regno, u32 id, 2110 enum bpf_reg_type type) 2111 { 2112 struct bpf_reg_state *reg = ®s[regno]; 2113 2114 if (reg->type == PTR_TO_MAP_VALUE_OR_NULL && reg->id == id) { 2115 reg->type = type; 2116 /* We don't need id from this point onwards anymore, thus we 2117 * should better reset it, so that state pruning has chances 2118 * to take effect. 2119 */ 2120 reg->id = 0; 2121 if (type == UNKNOWN_VALUE) 2122 __mark_reg_unknown_value(regs, regno); 2123 } 2124 } 2125 2126 /* The logic is similar to find_good_pkt_pointers(), both could eventually 2127 * be folded together at some point. 2128 */ 2129 static void mark_map_regs(struct bpf_verifier_state *state, u32 regno, 2130 enum bpf_reg_type type) 2131 { 2132 struct bpf_reg_state *regs = state->regs; 2133 u32 id = regs[regno].id; 2134 int i; 2135 2136 for (i = 0; i < MAX_BPF_REG; i++) 2137 mark_map_reg(regs, i, id, type); 2138 2139 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 2140 if (state->stack_slot_type[i] != STACK_SPILL) 2141 continue; 2142 mark_map_reg(state->spilled_regs, i / BPF_REG_SIZE, id, type); 2143 } 2144 } 2145 2146 static int check_cond_jmp_op(struct bpf_verifier_env *env, 2147 struct bpf_insn *insn, int *insn_idx) 2148 { 2149 struct bpf_verifier_state *other_branch, *this_branch = &env->cur_state; 2150 struct bpf_reg_state *regs = this_branch->regs, *dst_reg; 2151 u8 opcode = BPF_OP(insn->code); 2152 int err; 2153 2154 if (opcode > BPF_EXIT) { 2155 verbose("invalid BPF_JMP opcode %x\n", opcode); 2156 return -EINVAL; 2157 } 2158 2159 if (BPF_SRC(insn->code) == BPF_X) { 2160 if (insn->imm != 0) { 2161 verbose("BPF_JMP uses reserved fields\n"); 2162 return -EINVAL; 2163 } 2164 2165 /* check src1 operand */ 2166 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2167 if (err) 2168 return err; 2169 2170 if (is_pointer_value(env, insn->src_reg)) { 2171 verbose("R%d pointer comparison prohibited\n", 2172 insn->src_reg); 2173 return -EACCES; 2174 } 2175 } else { 2176 if (insn->src_reg != BPF_REG_0) { 2177 verbose("BPF_JMP uses reserved fields\n"); 2178 return -EINVAL; 2179 } 2180 } 2181 2182 /* check src2 operand */ 2183 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 2184 if (err) 2185 return err; 2186 2187 dst_reg = ®s[insn->dst_reg]; 2188 2189 /* detect if R == 0 where R was initialized to zero earlier */ 2190 if (BPF_SRC(insn->code) == BPF_K && 2191 (opcode == BPF_JEQ || opcode == BPF_JNE) && 2192 dst_reg->type == CONST_IMM && dst_reg->imm == insn->imm) { 2193 if (opcode == BPF_JEQ) { 2194 /* if (imm == imm) goto pc+off; 2195 * only follow the goto, ignore fall-through 2196 */ 2197 *insn_idx += insn->off; 2198 return 0; 2199 } else { 2200 /* if (imm != imm) goto pc+off; 2201 * only follow fall-through branch, since 2202 * that's where the program will go 2203 */ 2204 return 0; 2205 } 2206 } 2207 2208 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx); 2209 if (!other_branch) 2210 return -EFAULT; 2211 2212 /* detect if we are comparing against a constant value so we can adjust 2213 * our min/max values for our dst register. 2214 */ 2215 if (BPF_SRC(insn->code) == BPF_X) { 2216 if (regs[insn->src_reg].type == CONST_IMM) 2217 reg_set_min_max(&other_branch->regs[insn->dst_reg], 2218 dst_reg, regs[insn->src_reg].imm, 2219 opcode); 2220 else if (dst_reg->type == CONST_IMM) 2221 reg_set_min_max_inv(&other_branch->regs[insn->src_reg], 2222 ®s[insn->src_reg], dst_reg->imm, 2223 opcode); 2224 } else { 2225 reg_set_min_max(&other_branch->regs[insn->dst_reg], 2226 dst_reg, insn->imm, opcode); 2227 } 2228 2229 /* detect if R == 0 where R is returned from bpf_map_lookup_elem() */ 2230 if (BPF_SRC(insn->code) == BPF_K && 2231 insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) && 2232 dst_reg->type == PTR_TO_MAP_VALUE_OR_NULL) { 2233 /* Mark all identical map registers in each branch as either 2234 * safe or unknown depending R == 0 or R != 0 conditional. 2235 */ 2236 mark_map_regs(this_branch, insn->dst_reg, 2237 opcode == BPF_JEQ ? PTR_TO_MAP_VALUE : UNKNOWN_VALUE); 2238 mark_map_regs(other_branch, insn->dst_reg, 2239 opcode == BPF_JEQ ? UNKNOWN_VALUE : PTR_TO_MAP_VALUE); 2240 } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT && 2241 dst_reg->type == PTR_TO_PACKET && 2242 regs[insn->src_reg].type == PTR_TO_PACKET_END) { 2243 find_good_pkt_pointers(this_branch, dst_reg); 2244 } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGE && 2245 dst_reg->type == PTR_TO_PACKET_END && 2246 regs[insn->src_reg].type == PTR_TO_PACKET) { 2247 find_good_pkt_pointers(other_branch, ®s[insn->src_reg]); 2248 } else if (is_pointer_value(env, insn->dst_reg)) { 2249 verbose("R%d pointer comparison prohibited\n", insn->dst_reg); 2250 return -EACCES; 2251 } 2252 if (log_level) 2253 print_verifier_state(this_branch); 2254 return 0; 2255 } 2256 2257 /* return the map pointer stored inside BPF_LD_IMM64 instruction */ 2258 static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn) 2259 { 2260 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32; 2261 2262 return (struct bpf_map *) (unsigned long) imm64; 2263 } 2264 2265 /* verify BPF_LD_IMM64 instruction */ 2266 static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn) 2267 { 2268 struct bpf_reg_state *regs = env->cur_state.regs; 2269 int err; 2270 2271 if (BPF_SIZE(insn->code) != BPF_DW) { 2272 verbose("invalid BPF_LD_IMM insn\n"); 2273 return -EINVAL; 2274 } 2275 if (insn->off != 0) { 2276 verbose("BPF_LD_IMM64 uses reserved fields\n"); 2277 return -EINVAL; 2278 } 2279 2280 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 2281 if (err) 2282 return err; 2283 2284 if (insn->src_reg == 0) { 2285 u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm; 2286 2287 regs[insn->dst_reg].type = CONST_IMM; 2288 regs[insn->dst_reg].imm = imm; 2289 return 0; 2290 } 2291 2292 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */ 2293 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD); 2294 2295 regs[insn->dst_reg].type = CONST_PTR_TO_MAP; 2296 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn); 2297 return 0; 2298 } 2299 2300 static bool may_access_skb(enum bpf_prog_type type) 2301 { 2302 switch (type) { 2303 case BPF_PROG_TYPE_SOCKET_FILTER: 2304 case BPF_PROG_TYPE_SCHED_CLS: 2305 case BPF_PROG_TYPE_SCHED_ACT: 2306 return true; 2307 default: 2308 return false; 2309 } 2310 } 2311 2312 /* verify safety of LD_ABS|LD_IND instructions: 2313 * - they can only appear in the programs where ctx == skb 2314 * - since they are wrappers of function calls, they scratch R1-R5 registers, 2315 * preserve R6-R9, and store return value into R0 2316 * 2317 * Implicit input: 2318 * ctx == skb == R6 == CTX 2319 * 2320 * Explicit input: 2321 * SRC == any register 2322 * IMM == 32-bit immediate 2323 * 2324 * Output: 2325 * R0 - 8/16/32-bit skb data converted to cpu endianness 2326 */ 2327 static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn) 2328 { 2329 struct bpf_reg_state *regs = env->cur_state.regs; 2330 u8 mode = BPF_MODE(insn->code); 2331 struct bpf_reg_state *reg; 2332 int i, err; 2333 2334 if (!may_access_skb(env->prog->type)) { 2335 verbose("BPF_LD_[ABS|IND] instructions not allowed for this program type\n"); 2336 return -EINVAL; 2337 } 2338 2339 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 || 2340 BPF_SIZE(insn->code) == BPF_DW || 2341 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) { 2342 verbose("BPF_LD_[ABS|IND] uses reserved fields\n"); 2343 return -EINVAL; 2344 } 2345 2346 /* check whether implicit source operand (register R6) is readable */ 2347 err = check_reg_arg(regs, BPF_REG_6, SRC_OP); 2348 if (err) 2349 return err; 2350 2351 if (regs[BPF_REG_6].type != PTR_TO_CTX) { 2352 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n"); 2353 return -EINVAL; 2354 } 2355 2356 if (mode == BPF_IND) { 2357 /* check explicit source operand */ 2358 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2359 if (err) 2360 return err; 2361 } 2362 2363 /* reset caller saved regs to unreadable */ 2364 for (i = 0; i < CALLER_SAVED_REGS; i++) { 2365 reg = regs + caller_saved[i]; 2366 reg->type = NOT_INIT; 2367 reg->imm = 0; 2368 } 2369 2370 /* mark destination R0 register as readable, since it contains 2371 * the value fetched from the packet 2372 */ 2373 regs[BPF_REG_0].type = UNKNOWN_VALUE; 2374 return 0; 2375 } 2376 2377 /* non-recursive DFS pseudo code 2378 * 1 procedure DFS-iterative(G,v): 2379 * 2 label v as discovered 2380 * 3 let S be a stack 2381 * 4 S.push(v) 2382 * 5 while S is not empty 2383 * 6 t <- S.pop() 2384 * 7 if t is what we're looking for: 2385 * 8 return t 2386 * 9 for all edges e in G.adjacentEdges(t) do 2387 * 10 if edge e is already labelled 2388 * 11 continue with the next edge 2389 * 12 w <- G.adjacentVertex(t,e) 2390 * 13 if vertex w is not discovered and not explored 2391 * 14 label e as tree-edge 2392 * 15 label w as discovered 2393 * 16 S.push(w) 2394 * 17 continue at 5 2395 * 18 else if vertex w is discovered 2396 * 19 label e as back-edge 2397 * 20 else 2398 * 21 // vertex w is explored 2399 * 22 label e as forward- or cross-edge 2400 * 23 label t as explored 2401 * 24 S.pop() 2402 * 2403 * convention: 2404 * 0x10 - discovered 2405 * 0x11 - discovered and fall-through edge labelled 2406 * 0x12 - discovered and fall-through and branch edges labelled 2407 * 0x20 - explored 2408 */ 2409 2410 enum { 2411 DISCOVERED = 0x10, 2412 EXPLORED = 0x20, 2413 FALLTHROUGH = 1, 2414 BRANCH = 2, 2415 }; 2416 2417 #define STATE_LIST_MARK ((struct bpf_verifier_state_list *) -1L) 2418 2419 static int *insn_stack; /* stack of insns to process */ 2420 static int cur_stack; /* current stack index */ 2421 static int *insn_state; 2422 2423 /* t, w, e - match pseudo-code above: 2424 * t - index of current instruction 2425 * w - next instruction 2426 * e - edge 2427 */ 2428 static int push_insn(int t, int w, int e, struct bpf_verifier_env *env) 2429 { 2430 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH)) 2431 return 0; 2432 2433 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH)) 2434 return 0; 2435 2436 if (w < 0 || w >= env->prog->len) { 2437 verbose("jump out of range from insn %d to %d\n", t, w); 2438 return -EINVAL; 2439 } 2440 2441 if (e == BRANCH) 2442 /* mark branch target for state pruning */ 2443 env->explored_states[w] = STATE_LIST_MARK; 2444 2445 if (insn_state[w] == 0) { 2446 /* tree-edge */ 2447 insn_state[t] = DISCOVERED | e; 2448 insn_state[w] = DISCOVERED; 2449 if (cur_stack >= env->prog->len) 2450 return -E2BIG; 2451 insn_stack[cur_stack++] = w; 2452 return 1; 2453 } else if ((insn_state[w] & 0xF0) == DISCOVERED) { 2454 verbose("back-edge from insn %d to %d\n", t, w); 2455 return -EINVAL; 2456 } else if (insn_state[w] == EXPLORED) { 2457 /* forward- or cross-edge */ 2458 insn_state[t] = DISCOVERED | e; 2459 } else { 2460 verbose("insn state internal bug\n"); 2461 return -EFAULT; 2462 } 2463 return 0; 2464 } 2465 2466 /* non-recursive depth-first-search to detect loops in BPF program 2467 * loop == back-edge in directed graph 2468 */ 2469 static int check_cfg(struct bpf_verifier_env *env) 2470 { 2471 struct bpf_insn *insns = env->prog->insnsi; 2472 int insn_cnt = env->prog->len; 2473 int ret = 0; 2474 int i, t; 2475 2476 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 2477 if (!insn_state) 2478 return -ENOMEM; 2479 2480 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 2481 if (!insn_stack) { 2482 kfree(insn_state); 2483 return -ENOMEM; 2484 } 2485 2486 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */ 2487 insn_stack[0] = 0; /* 0 is the first instruction */ 2488 cur_stack = 1; 2489 2490 peek_stack: 2491 if (cur_stack == 0) 2492 goto check_state; 2493 t = insn_stack[cur_stack - 1]; 2494 2495 if (BPF_CLASS(insns[t].code) == BPF_JMP) { 2496 u8 opcode = BPF_OP(insns[t].code); 2497 2498 if (opcode == BPF_EXIT) { 2499 goto mark_explored; 2500 } else if (opcode == BPF_CALL) { 2501 ret = push_insn(t, t + 1, FALLTHROUGH, env); 2502 if (ret == 1) 2503 goto peek_stack; 2504 else if (ret < 0) 2505 goto err_free; 2506 if (t + 1 < insn_cnt) 2507 env->explored_states[t + 1] = STATE_LIST_MARK; 2508 } else if (opcode == BPF_JA) { 2509 if (BPF_SRC(insns[t].code) != BPF_K) { 2510 ret = -EINVAL; 2511 goto err_free; 2512 } 2513 /* unconditional jump with single edge */ 2514 ret = push_insn(t, t + insns[t].off + 1, 2515 FALLTHROUGH, env); 2516 if (ret == 1) 2517 goto peek_stack; 2518 else if (ret < 0) 2519 goto err_free; 2520 /* tell verifier to check for equivalent states 2521 * after every call and jump 2522 */ 2523 if (t + 1 < insn_cnt) 2524 env->explored_states[t + 1] = STATE_LIST_MARK; 2525 } else { 2526 /* conditional jump with two edges */ 2527 ret = push_insn(t, t + 1, FALLTHROUGH, env); 2528 if (ret == 1) 2529 goto peek_stack; 2530 else if (ret < 0) 2531 goto err_free; 2532 2533 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env); 2534 if (ret == 1) 2535 goto peek_stack; 2536 else if (ret < 0) 2537 goto err_free; 2538 } 2539 } else { 2540 /* all other non-branch instructions with single 2541 * fall-through edge 2542 */ 2543 ret = push_insn(t, t + 1, FALLTHROUGH, env); 2544 if (ret == 1) 2545 goto peek_stack; 2546 else if (ret < 0) 2547 goto err_free; 2548 } 2549 2550 mark_explored: 2551 insn_state[t] = EXPLORED; 2552 if (cur_stack-- <= 0) { 2553 verbose("pop stack internal bug\n"); 2554 ret = -EFAULT; 2555 goto err_free; 2556 } 2557 goto peek_stack; 2558 2559 check_state: 2560 for (i = 0; i < insn_cnt; i++) { 2561 if (insn_state[i] != EXPLORED) { 2562 verbose("unreachable insn %d\n", i); 2563 ret = -EINVAL; 2564 goto err_free; 2565 } 2566 } 2567 ret = 0; /* cfg looks good */ 2568 2569 err_free: 2570 kfree(insn_state); 2571 kfree(insn_stack); 2572 return ret; 2573 } 2574 2575 /* the following conditions reduce the number of explored insns 2576 * from ~140k to ~80k for ultra large programs that use a lot of ptr_to_packet 2577 */ 2578 static bool compare_ptrs_to_packet(struct bpf_reg_state *old, 2579 struct bpf_reg_state *cur) 2580 { 2581 if (old->id != cur->id) 2582 return false; 2583 2584 /* old ptr_to_packet is more conservative, since it allows smaller 2585 * range. Ex: 2586 * old(off=0,r=10) is equal to cur(off=0,r=20), because 2587 * old(off=0,r=10) means that with range=10 the verifier proceeded 2588 * further and found no issues with the program. Now we're in the same 2589 * spot with cur(off=0,r=20), so we're safe too, since anything further 2590 * will only be looking at most 10 bytes after this pointer. 2591 */ 2592 if (old->off == cur->off && old->range < cur->range) 2593 return true; 2594 2595 /* old(off=20,r=10) is equal to cur(off=22,re=22 or 5 or 0) 2596 * since both cannot be used for packet access and safe(old) 2597 * pointer has smaller off that could be used for further 2598 * 'if (ptr > data_end)' check 2599 * Ex: 2600 * old(off=20,r=10) and cur(off=22,r=22) and cur(off=22,r=0) mean 2601 * that we cannot access the packet. 2602 * The safe range is: 2603 * [ptr, ptr + range - off) 2604 * so whenever off >=range, it means no safe bytes from this pointer. 2605 * When comparing old->off <= cur->off, it means that older code 2606 * went with smaller offset and that offset was later 2607 * used to figure out the safe range after 'if (ptr > data_end)' check 2608 * Say, 'old' state was explored like: 2609 * ... R3(off=0, r=0) 2610 * R4 = R3 + 20 2611 * ... now R4(off=20,r=0) <-- here 2612 * if (R4 > data_end) 2613 * ... R4(off=20,r=20), R3(off=0,r=20) and R3 can be used to access. 2614 * ... the code further went all the way to bpf_exit. 2615 * Now the 'cur' state at the mark 'here' has R4(off=30,r=0). 2616 * old_R4(off=20,r=0) equal to cur_R4(off=30,r=0), since if the verifier 2617 * goes further, such cur_R4 will give larger safe packet range after 2618 * 'if (R4 > data_end)' and all further insn were already good with r=20, 2619 * so they will be good with r=30 and we can prune the search. 2620 */ 2621 if (old->off <= cur->off && 2622 old->off >= old->range && cur->off >= cur->range) 2623 return true; 2624 2625 return false; 2626 } 2627 2628 /* compare two verifier states 2629 * 2630 * all states stored in state_list are known to be valid, since 2631 * verifier reached 'bpf_exit' instruction through them 2632 * 2633 * this function is called when verifier exploring different branches of 2634 * execution popped from the state stack. If it sees an old state that has 2635 * more strict register state and more strict stack state then this execution 2636 * branch doesn't need to be explored further, since verifier already 2637 * concluded that more strict state leads to valid finish. 2638 * 2639 * Therefore two states are equivalent if register state is more conservative 2640 * and explored stack state is more conservative than the current one. 2641 * Example: 2642 * explored current 2643 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC) 2644 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC) 2645 * 2646 * In other words if current stack state (one being explored) has more 2647 * valid slots than old one that already passed validation, it means 2648 * the verifier can stop exploring and conclude that current state is valid too 2649 * 2650 * Similarly with registers. If explored state has register type as invalid 2651 * whereas register type in current state is meaningful, it means that 2652 * the current state will reach 'bpf_exit' instruction safely 2653 */ 2654 static bool states_equal(struct bpf_verifier_env *env, 2655 struct bpf_verifier_state *old, 2656 struct bpf_verifier_state *cur) 2657 { 2658 bool varlen_map_access = env->varlen_map_value_access; 2659 struct bpf_reg_state *rold, *rcur; 2660 int i; 2661 2662 for (i = 0; i < MAX_BPF_REG; i++) { 2663 rold = &old->regs[i]; 2664 rcur = &cur->regs[i]; 2665 2666 if (memcmp(rold, rcur, sizeof(*rold)) == 0) 2667 continue; 2668 2669 /* If the ranges were not the same, but everything else was and 2670 * we didn't do a variable access into a map then we are a-ok. 2671 */ 2672 if (!varlen_map_access && 2673 memcmp(rold, rcur, offsetofend(struct bpf_reg_state, id)) == 0) 2674 continue; 2675 2676 /* If we didn't map access then again we don't care about the 2677 * mismatched range values and it's ok if our old type was 2678 * UNKNOWN and we didn't go to a NOT_INIT'ed reg. 2679 */ 2680 if (rold->type == NOT_INIT || 2681 (!varlen_map_access && rold->type == UNKNOWN_VALUE && 2682 rcur->type != NOT_INIT)) 2683 continue; 2684 2685 if (rold->type == PTR_TO_PACKET && rcur->type == PTR_TO_PACKET && 2686 compare_ptrs_to_packet(rold, rcur)) 2687 continue; 2688 2689 return false; 2690 } 2691 2692 for (i = 0; i < MAX_BPF_STACK; i++) { 2693 if (old->stack_slot_type[i] == STACK_INVALID) 2694 continue; 2695 if (old->stack_slot_type[i] != cur->stack_slot_type[i]) 2696 /* Ex: old explored (safe) state has STACK_SPILL in 2697 * this stack slot, but current has has STACK_MISC -> 2698 * this verifier states are not equivalent, 2699 * return false to continue verification of this path 2700 */ 2701 return false; 2702 if (i % BPF_REG_SIZE) 2703 continue; 2704 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE], 2705 &cur->spilled_regs[i / BPF_REG_SIZE], 2706 sizeof(old->spilled_regs[0]))) 2707 /* when explored and current stack slot types are 2708 * the same, check that stored pointers types 2709 * are the same as well. 2710 * Ex: explored safe path could have stored 2711 * (bpf_reg_state) {.type = PTR_TO_STACK, .imm = -8} 2712 * but current path has stored: 2713 * (bpf_reg_state) {.type = PTR_TO_STACK, .imm = -16} 2714 * such verifier states are not equivalent. 2715 * return false to continue verification of this path 2716 */ 2717 return false; 2718 else 2719 continue; 2720 } 2721 return true; 2722 } 2723 2724 static int is_state_visited(struct bpf_verifier_env *env, int insn_idx) 2725 { 2726 struct bpf_verifier_state_list *new_sl; 2727 struct bpf_verifier_state_list *sl; 2728 2729 sl = env->explored_states[insn_idx]; 2730 if (!sl) 2731 /* this 'insn_idx' instruction wasn't marked, so we will not 2732 * be doing state search here 2733 */ 2734 return 0; 2735 2736 while (sl != STATE_LIST_MARK) { 2737 if (states_equal(env, &sl->state, &env->cur_state)) 2738 /* reached equivalent register/stack state, 2739 * prune the search 2740 */ 2741 return 1; 2742 sl = sl->next; 2743 } 2744 2745 /* there were no equivalent states, remember current one. 2746 * technically the current state is not proven to be safe yet, 2747 * but it will either reach bpf_exit (which means it's safe) or 2748 * it will be rejected. Since there are no loops, we won't be 2749 * seeing this 'insn_idx' instruction again on the way to bpf_exit 2750 */ 2751 new_sl = kmalloc(sizeof(struct bpf_verifier_state_list), GFP_USER); 2752 if (!new_sl) 2753 return -ENOMEM; 2754 2755 /* add new state to the head of linked list */ 2756 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state)); 2757 new_sl->next = env->explored_states[insn_idx]; 2758 env->explored_states[insn_idx] = new_sl; 2759 return 0; 2760 } 2761 2762 static int ext_analyzer_insn_hook(struct bpf_verifier_env *env, 2763 int insn_idx, int prev_insn_idx) 2764 { 2765 if (!env->analyzer_ops || !env->analyzer_ops->insn_hook) 2766 return 0; 2767 2768 return env->analyzer_ops->insn_hook(env, insn_idx, prev_insn_idx); 2769 } 2770 2771 static int do_check(struct bpf_verifier_env *env) 2772 { 2773 struct bpf_verifier_state *state = &env->cur_state; 2774 struct bpf_insn *insns = env->prog->insnsi; 2775 struct bpf_reg_state *regs = state->regs; 2776 int insn_cnt = env->prog->len; 2777 int insn_idx, prev_insn_idx = 0; 2778 int insn_processed = 0; 2779 bool do_print_state = false; 2780 2781 init_reg_state(regs); 2782 insn_idx = 0; 2783 env->varlen_map_value_access = false; 2784 for (;;) { 2785 struct bpf_insn *insn; 2786 u8 class; 2787 int err; 2788 2789 if (insn_idx >= insn_cnt) { 2790 verbose("invalid insn idx %d insn_cnt %d\n", 2791 insn_idx, insn_cnt); 2792 return -EFAULT; 2793 } 2794 2795 insn = &insns[insn_idx]; 2796 class = BPF_CLASS(insn->code); 2797 2798 if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) { 2799 verbose("BPF program is too large. Processed %d insn\n", 2800 insn_processed); 2801 return -E2BIG; 2802 } 2803 2804 err = is_state_visited(env, insn_idx); 2805 if (err < 0) 2806 return err; 2807 if (err == 1) { 2808 /* found equivalent state, can prune the search */ 2809 if (log_level) { 2810 if (do_print_state) 2811 verbose("\nfrom %d to %d: safe\n", 2812 prev_insn_idx, insn_idx); 2813 else 2814 verbose("%d: safe\n", insn_idx); 2815 } 2816 goto process_bpf_exit; 2817 } 2818 2819 if (log_level && do_print_state) { 2820 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx); 2821 print_verifier_state(&env->cur_state); 2822 do_print_state = false; 2823 } 2824 2825 if (log_level) { 2826 verbose("%d: ", insn_idx); 2827 print_bpf_insn(insn); 2828 } 2829 2830 err = ext_analyzer_insn_hook(env, insn_idx, prev_insn_idx); 2831 if (err) 2832 return err; 2833 2834 if (class == BPF_ALU || class == BPF_ALU64) { 2835 err = check_alu_op(env, insn); 2836 if (err) 2837 return err; 2838 2839 } else if (class == BPF_LDX) { 2840 enum bpf_reg_type *prev_src_type, src_reg_type; 2841 2842 /* check for reserved fields is already done */ 2843 2844 /* check src operand */ 2845 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2846 if (err) 2847 return err; 2848 2849 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); 2850 if (err) 2851 return err; 2852 2853 src_reg_type = regs[insn->src_reg].type; 2854 2855 /* check that memory (src_reg + off) is readable, 2856 * the state of dst_reg will be updated by this func 2857 */ 2858 err = check_mem_access(env, insn->src_reg, insn->off, 2859 BPF_SIZE(insn->code), BPF_READ, 2860 insn->dst_reg); 2861 if (err) 2862 return err; 2863 2864 if (BPF_SIZE(insn->code) != BPF_W && 2865 BPF_SIZE(insn->code) != BPF_DW) { 2866 insn_idx++; 2867 continue; 2868 } 2869 2870 prev_src_type = &env->insn_aux_data[insn_idx].ptr_type; 2871 2872 if (*prev_src_type == NOT_INIT) { 2873 /* saw a valid insn 2874 * dst_reg = *(u32 *)(src_reg + off) 2875 * save type to validate intersecting paths 2876 */ 2877 *prev_src_type = src_reg_type; 2878 2879 } else if (src_reg_type != *prev_src_type && 2880 (src_reg_type == PTR_TO_CTX || 2881 *prev_src_type == PTR_TO_CTX)) { 2882 /* ABuser program is trying to use the same insn 2883 * dst_reg = *(u32*) (src_reg + off) 2884 * with different pointer types: 2885 * src_reg == ctx in one branch and 2886 * src_reg == stack|map in some other branch. 2887 * Reject it. 2888 */ 2889 verbose("same insn cannot be used with different pointers\n"); 2890 return -EINVAL; 2891 } 2892 2893 } else if (class == BPF_STX) { 2894 enum bpf_reg_type *prev_dst_type, dst_reg_type; 2895 2896 if (BPF_MODE(insn->code) == BPF_XADD) { 2897 err = check_xadd(env, insn); 2898 if (err) 2899 return err; 2900 insn_idx++; 2901 continue; 2902 } 2903 2904 /* check src1 operand */ 2905 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2906 if (err) 2907 return err; 2908 /* check src2 operand */ 2909 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 2910 if (err) 2911 return err; 2912 2913 dst_reg_type = regs[insn->dst_reg].type; 2914 2915 /* check that memory (dst_reg + off) is writeable */ 2916 err = check_mem_access(env, insn->dst_reg, insn->off, 2917 BPF_SIZE(insn->code), BPF_WRITE, 2918 insn->src_reg); 2919 if (err) 2920 return err; 2921 2922 prev_dst_type = &env->insn_aux_data[insn_idx].ptr_type; 2923 2924 if (*prev_dst_type == NOT_INIT) { 2925 *prev_dst_type = dst_reg_type; 2926 } else if (dst_reg_type != *prev_dst_type && 2927 (dst_reg_type == PTR_TO_CTX || 2928 *prev_dst_type == PTR_TO_CTX)) { 2929 verbose("same insn cannot be used with different pointers\n"); 2930 return -EINVAL; 2931 } 2932 2933 } else if (class == BPF_ST) { 2934 if (BPF_MODE(insn->code) != BPF_MEM || 2935 insn->src_reg != BPF_REG_0) { 2936 verbose("BPF_ST uses reserved fields\n"); 2937 return -EINVAL; 2938 } 2939 /* check src operand */ 2940 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 2941 if (err) 2942 return err; 2943 2944 /* check that memory (dst_reg + off) is writeable */ 2945 err = check_mem_access(env, insn->dst_reg, insn->off, 2946 BPF_SIZE(insn->code), BPF_WRITE, 2947 -1); 2948 if (err) 2949 return err; 2950 2951 } else if (class == BPF_JMP) { 2952 u8 opcode = BPF_OP(insn->code); 2953 2954 if (opcode == BPF_CALL) { 2955 if (BPF_SRC(insn->code) != BPF_K || 2956 insn->off != 0 || 2957 insn->src_reg != BPF_REG_0 || 2958 insn->dst_reg != BPF_REG_0) { 2959 verbose("BPF_CALL uses reserved fields\n"); 2960 return -EINVAL; 2961 } 2962 2963 err = check_call(env, insn->imm); 2964 if (err) 2965 return err; 2966 2967 } else if (opcode == BPF_JA) { 2968 if (BPF_SRC(insn->code) != BPF_K || 2969 insn->imm != 0 || 2970 insn->src_reg != BPF_REG_0 || 2971 insn->dst_reg != BPF_REG_0) { 2972 verbose("BPF_JA uses reserved fields\n"); 2973 return -EINVAL; 2974 } 2975 2976 insn_idx += insn->off + 1; 2977 continue; 2978 2979 } else if (opcode == BPF_EXIT) { 2980 if (BPF_SRC(insn->code) != BPF_K || 2981 insn->imm != 0 || 2982 insn->src_reg != BPF_REG_0 || 2983 insn->dst_reg != BPF_REG_0) { 2984 verbose("BPF_EXIT uses reserved fields\n"); 2985 return -EINVAL; 2986 } 2987 2988 /* eBPF calling convetion is such that R0 is used 2989 * to return the value from eBPF program. 2990 * Make sure that it's readable at this time 2991 * of bpf_exit, which means that program wrote 2992 * something into it earlier 2993 */ 2994 err = check_reg_arg(regs, BPF_REG_0, SRC_OP); 2995 if (err) 2996 return err; 2997 2998 if (is_pointer_value(env, BPF_REG_0)) { 2999 verbose("R0 leaks addr as return value\n"); 3000 return -EACCES; 3001 } 3002 3003 process_bpf_exit: 3004 insn_idx = pop_stack(env, &prev_insn_idx); 3005 if (insn_idx < 0) { 3006 break; 3007 } else { 3008 do_print_state = true; 3009 continue; 3010 } 3011 } else { 3012 err = check_cond_jmp_op(env, insn, &insn_idx); 3013 if (err) 3014 return err; 3015 } 3016 } else if (class == BPF_LD) { 3017 u8 mode = BPF_MODE(insn->code); 3018 3019 if (mode == BPF_ABS || mode == BPF_IND) { 3020 err = check_ld_abs(env, insn); 3021 if (err) 3022 return err; 3023 3024 } else if (mode == BPF_IMM) { 3025 err = check_ld_imm(env, insn); 3026 if (err) 3027 return err; 3028 3029 insn_idx++; 3030 } else { 3031 verbose("invalid BPF_LD mode\n"); 3032 return -EINVAL; 3033 } 3034 reset_reg_range_values(regs, insn->dst_reg); 3035 } else { 3036 verbose("unknown insn class %d\n", class); 3037 return -EINVAL; 3038 } 3039 3040 insn_idx++; 3041 } 3042 3043 verbose("processed %d insns\n", insn_processed); 3044 return 0; 3045 } 3046 3047 static int check_map_prog_compatibility(struct bpf_map *map, 3048 struct bpf_prog *prog) 3049 3050 { 3051 if (prog->type == BPF_PROG_TYPE_PERF_EVENT && 3052 (map->map_type == BPF_MAP_TYPE_HASH || 3053 map->map_type == BPF_MAP_TYPE_PERCPU_HASH) && 3054 (map->map_flags & BPF_F_NO_PREALLOC)) { 3055 verbose("perf_event programs can only use preallocated hash map\n"); 3056 return -EINVAL; 3057 } 3058 return 0; 3059 } 3060 3061 /* look for pseudo eBPF instructions that access map FDs and 3062 * replace them with actual map pointers 3063 */ 3064 static int replace_map_fd_with_map_ptr(struct bpf_verifier_env *env) 3065 { 3066 struct bpf_insn *insn = env->prog->insnsi; 3067 int insn_cnt = env->prog->len; 3068 int i, j, err; 3069 3070 err = bpf_prog_calc_tag(env->prog); 3071 if (err) 3072 return err; 3073 3074 for (i = 0; i < insn_cnt; i++, insn++) { 3075 if (BPF_CLASS(insn->code) == BPF_LDX && 3076 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) { 3077 verbose("BPF_LDX uses reserved fields\n"); 3078 return -EINVAL; 3079 } 3080 3081 if (BPF_CLASS(insn->code) == BPF_STX && 3082 ((BPF_MODE(insn->code) != BPF_MEM && 3083 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) { 3084 verbose("BPF_STX uses reserved fields\n"); 3085 return -EINVAL; 3086 } 3087 3088 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) { 3089 struct bpf_map *map; 3090 struct fd f; 3091 3092 if (i == insn_cnt - 1 || insn[1].code != 0 || 3093 insn[1].dst_reg != 0 || insn[1].src_reg != 0 || 3094 insn[1].off != 0) { 3095 verbose("invalid bpf_ld_imm64 insn\n"); 3096 return -EINVAL; 3097 } 3098 3099 if (insn->src_reg == 0) 3100 /* valid generic load 64-bit imm */ 3101 goto next_insn; 3102 3103 if (insn->src_reg != BPF_PSEUDO_MAP_FD) { 3104 verbose("unrecognized bpf_ld_imm64 insn\n"); 3105 return -EINVAL; 3106 } 3107 3108 f = fdget(insn->imm); 3109 map = __bpf_map_get(f); 3110 if (IS_ERR(map)) { 3111 verbose("fd %d is not pointing to valid bpf_map\n", 3112 insn->imm); 3113 return PTR_ERR(map); 3114 } 3115 3116 err = check_map_prog_compatibility(map, env->prog); 3117 if (err) { 3118 fdput(f); 3119 return err; 3120 } 3121 3122 /* store map pointer inside BPF_LD_IMM64 instruction */ 3123 insn[0].imm = (u32) (unsigned long) map; 3124 insn[1].imm = ((u64) (unsigned long) map) >> 32; 3125 3126 /* check whether we recorded this map already */ 3127 for (j = 0; j < env->used_map_cnt; j++) 3128 if (env->used_maps[j] == map) { 3129 fdput(f); 3130 goto next_insn; 3131 } 3132 3133 if (env->used_map_cnt >= MAX_USED_MAPS) { 3134 fdput(f); 3135 return -E2BIG; 3136 } 3137 3138 /* hold the map. If the program is rejected by verifier, 3139 * the map will be released by release_maps() or it 3140 * will be used by the valid program until it's unloaded 3141 * and all maps are released in free_bpf_prog_info() 3142 */ 3143 map = bpf_map_inc(map, false); 3144 if (IS_ERR(map)) { 3145 fdput(f); 3146 return PTR_ERR(map); 3147 } 3148 env->used_maps[env->used_map_cnt++] = map; 3149 3150 fdput(f); 3151 next_insn: 3152 insn++; 3153 i++; 3154 } 3155 } 3156 3157 /* now all pseudo BPF_LD_IMM64 instructions load valid 3158 * 'struct bpf_map *' into a register instead of user map_fd. 3159 * These pointers will be used later by verifier to validate map access. 3160 */ 3161 return 0; 3162 } 3163 3164 /* drop refcnt of maps used by the rejected program */ 3165 static void release_maps(struct bpf_verifier_env *env) 3166 { 3167 int i; 3168 3169 for (i = 0; i < env->used_map_cnt; i++) 3170 bpf_map_put(env->used_maps[i]); 3171 } 3172 3173 /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */ 3174 static void convert_pseudo_ld_imm64(struct bpf_verifier_env *env) 3175 { 3176 struct bpf_insn *insn = env->prog->insnsi; 3177 int insn_cnt = env->prog->len; 3178 int i; 3179 3180 for (i = 0; i < insn_cnt; i++, insn++) 3181 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW)) 3182 insn->src_reg = 0; 3183 } 3184 3185 /* convert load instructions that access fields of 'struct __sk_buff' 3186 * into sequence of instructions that access fields of 'struct sk_buff' 3187 */ 3188 static int convert_ctx_accesses(struct bpf_verifier_env *env) 3189 { 3190 const struct bpf_verifier_ops *ops = env->prog->aux->ops; 3191 const int insn_cnt = env->prog->len; 3192 struct bpf_insn insn_buf[16], *insn; 3193 struct bpf_prog *new_prog; 3194 enum bpf_access_type type; 3195 int i, cnt, delta = 0; 3196 3197 if (ops->gen_prologue) { 3198 cnt = ops->gen_prologue(insn_buf, env->seen_direct_write, 3199 env->prog); 3200 if (cnt >= ARRAY_SIZE(insn_buf)) { 3201 verbose("bpf verifier is misconfigured\n"); 3202 return -EINVAL; 3203 } else if (cnt) { 3204 new_prog = bpf_patch_insn_single(env->prog, 0, 3205 insn_buf, cnt); 3206 if (!new_prog) 3207 return -ENOMEM; 3208 env->prog = new_prog; 3209 delta += cnt - 1; 3210 } 3211 } 3212 3213 if (!ops->convert_ctx_access) 3214 return 0; 3215 3216 insn = env->prog->insnsi + delta; 3217 3218 for (i = 0; i < insn_cnt; i++, insn++) { 3219 if (insn->code == (BPF_LDX | BPF_MEM | BPF_B) || 3220 insn->code == (BPF_LDX | BPF_MEM | BPF_H) || 3221 insn->code == (BPF_LDX | BPF_MEM | BPF_W) || 3222 insn->code == (BPF_LDX | BPF_MEM | BPF_DW)) 3223 type = BPF_READ; 3224 else if (insn->code == (BPF_STX | BPF_MEM | BPF_B) || 3225 insn->code == (BPF_STX | BPF_MEM | BPF_H) || 3226 insn->code == (BPF_STX | BPF_MEM | BPF_W) || 3227 insn->code == (BPF_STX | BPF_MEM | BPF_DW)) 3228 type = BPF_WRITE; 3229 else 3230 continue; 3231 3232 if (env->insn_aux_data[i].ptr_type != PTR_TO_CTX) 3233 continue; 3234 3235 cnt = ops->convert_ctx_access(type, insn, insn_buf, env->prog); 3236 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) { 3237 verbose("bpf verifier is misconfigured\n"); 3238 return -EINVAL; 3239 } 3240 3241 new_prog = bpf_patch_insn_single(env->prog, i + delta, insn_buf, 3242 cnt); 3243 if (!new_prog) 3244 return -ENOMEM; 3245 3246 delta += cnt - 1; 3247 3248 /* keep walking new program and skip insns we just inserted */ 3249 env->prog = new_prog; 3250 insn = new_prog->insnsi + i + delta; 3251 } 3252 3253 return 0; 3254 } 3255 3256 static void free_states(struct bpf_verifier_env *env) 3257 { 3258 struct bpf_verifier_state_list *sl, *sln; 3259 int i; 3260 3261 if (!env->explored_states) 3262 return; 3263 3264 for (i = 0; i < env->prog->len; i++) { 3265 sl = env->explored_states[i]; 3266 3267 if (sl) 3268 while (sl != STATE_LIST_MARK) { 3269 sln = sl->next; 3270 kfree(sl); 3271 sl = sln; 3272 } 3273 } 3274 3275 kfree(env->explored_states); 3276 } 3277 3278 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) 3279 { 3280 char __user *log_ubuf = NULL; 3281 struct bpf_verifier_env *env; 3282 int ret = -EINVAL; 3283 3284 /* 'struct bpf_verifier_env' can be global, but since it's not small, 3285 * allocate/free it every time bpf_check() is called 3286 */ 3287 env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL); 3288 if (!env) 3289 return -ENOMEM; 3290 3291 env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) * 3292 (*prog)->len); 3293 ret = -ENOMEM; 3294 if (!env->insn_aux_data) 3295 goto err_free_env; 3296 env->prog = *prog; 3297 3298 /* grab the mutex to protect few globals used by verifier */ 3299 mutex_lock(&bpf_verifier_lock); 3300 3301 if (attr->log_level || attr->log_buf || attr->log_size) { 3302 /* user requested verbose verifier output 3303 * and supplied buffer to store the verification trace 3304 */ 3305 log_level = attr->log_level; 3306 log_ubuf = (char __user *) (unsigned long) attr->log_buf; 3307 log_size = attr->log_size; 3308 log_len = 0; 3309 3310 ret = -EINVAL; 3311 /* log_* values have to be sane */ 3312 if (log_size < 128 || log_size > UINT_MAX >> 8 || 3313 log_level == 0 || log_ubuf == NULL) 3314 goto err_unlock; 3315 3316 ret = -ENOMEM; 3317 log_buf = vmalloc(log_size); 3318 if (!log_buf) 3319 goto err_unlock; 3320 } else { 3321 log_level = 0; 3322 } 3323 3324 ret = replace_map_fd_with_map_ptr(env); 3325 if (ret < 0) 3326 goto skip_full_check; 3327 3328 env->explored_states = kcalloc(env->prog->len, 3329 sizeof(struct bpf_verifier_state_list *), 3330 GFP_USER); 3331 ret = -ENOMEM; 3332 if (!env->explored_states) 3333 goto skip_full_check; 3334 3335 ret = check_cfg(env); 3336 if (ret < 0) 3337 goto skip_full_check; 3338 3339 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); 3340 3341 ret = do_check(env); 3342 3343 skip_full_check: 3344 while (pop_stack(env, NULL) >= 0); 3345 free_states(env); 3346 3347 if (ret == 0) 3348 /* program is valid, convert *(u32*)(ctx + off) accesses */ 3349 ret = convert_ctx_accesses(env); 3350 3351 if (log_level && log_len >= log_size - 1) { 3352 BUG_ON(log_len >= log_size); 3353 /* verifier log exceeded user supplied buffer */ 3354 ret = -ENOSPC; 3355 /* fall through to return what was recorded */ 3356 } 3357 3358 /* copy verifier log back to user space including trailing zero */ 3359 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) { 3360 ret = -EFAULT; 3361 goto free_log_buf; 3362 } 3363 3364 if (ret == 0 && env->used_map_cnt) { 3365 /* if program passed verifier, update used_maps in bpf_prog_info */ 3366 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt, 3367 sizeof(env->used_maps[0]), 3368 GFP_KERNEL); 3369 3370 if (!env->prog->aux->used_maps) { 3371 ret = -ENOMEM; 3372 goto free_log_buf; 3373 } 3374 3375 memcpy(env->prog->aux->used_maps, env->used_maps, 3376 sizeof(env->used_maps[0]) * env->used_map_cnt); 3377 env->prog->aux->used_map_cnt = env->used_map_cnt; 3378 3379 /* program is valid. Convert pseudo bpf_ld_imm64 into generic 3380 * bpf_ld_imm64 instructions 3381 */ 3382 convert_pseudo_ld_imm64(env); 3383 } 3384 3385 free_log_buf: 3386 if (log_level) 3387 vfree(log_buf); 3388 if (!env->prog->aux->used_maps) 3389 /* if we didn't copy map pointers into bpf_prog_info, release 3390 * them now. Otherwise free_bpf_prog_info() will release them. 3391 */ 3392 release_maps(env); 3393 *prog = env->prog; 3394 err_unlock: 3395 mutex_unlock(&bpf_verifier_lock); 3396 vfree(env->insn_aux_data); 3397 err_free_env: 3398 kfree(env); 3399 return ret; 3400 } 3401 3402 int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops, 3403 void *priv) 3404 { 3405 struct bpf_verifier_env *env; 3406 int ret; 3407 3408 env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL); 3409 if (!env) 3410 return -ENOMEM; 3411 3412 env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) * 3413 prog->len); 3414 ret = -ENOMEM; 3415 if (!env->insn_aux_data) 3416 goto err_free_env; 3417 env->prog = prog; 3418 env->analyzer_ops = ops; 3419 env->analyzer_priv = priv; 3420 3421 /* grab the mutex to protect few globals used by verifier */ 3422 mutex_lock(&bpf_verifier_lock); 3423 3424 log_level = 0; 3425 3426 env->explored_states = kcalloc(env->prog->len, 3427 sizeof(struct bpf_verifier_state_list *), 3428 GFP_KERNEL); 3429 ret = -ENOMEM; 3430 if (!env->explored_states) 3431 goto skip_full_check; 3432 3433 ret = check_cfg(env); 3434 if (ret < 0) 3435 goto skip_full_check; 3436 3437 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); 3438 3439 ret = do_check(env); 3440 3441 skip_full_check: 3442 while (pop_stack(env, NULL) >= 0); 3443 free_states(env); 3444 3445 mutex_unlock(&bpf_verifier_lock); 3446 vfree(env->insn_aux_data); 3447 err_free_env: 3448 kfree(env); 3449 return ret; 3450 } 3451 EXPORT_SYMBOL_GPL(bpf_analyzer); 3452