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 32k 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 BUG_ON(regno >= MAX_BPF_REG); 468 regs[regno].type = UNKNOWN_VALUE; 469 regs[regno].id = 0; 470 regs[regno].imm = 0; 471 } 472 473 static void reset_reg_range_values(struct bpf_reg_state *regs, u32 regno) 474 { 475 regs[regno].min_value = BPF_REGISTER_MIN_RANGE; 476 regs[regno].max_value = BPF_REGISTER_MAX_RANGE; 477 } 478 479 enum reg_arg_type { 480 SRC_OP, /* register is used as source operand */ 481 DST_OP, /* register is used as destination operand */ 482 DST_OP_NO_MARK /* same as above, check only, don't mark */ 483 }; 484 485 static int check_reg_arg(struct bpf_reg_state *regs, u32 regno, 486 enum reg_arg_type t) 487 { 488 if (regno >= MAX_BPF_REG) { 489 verbose("R%d is invalid\n", regno); 490 return -EINVAL; 491 } 492 493 if (t == SRC_OP) { 494 /* check whether register used as source operand can be read */ 495 if (regs[regno].type == NOT_INIT) { 496 verbose("R%d !read_ok\n", regno); 497 return -EACCES; 498 } 499 } else { 500 /* check whether register used as dest operand can be written to */ 501 if (regno == BPF_REG_FP) { 502 verbose("frame pointer is read only\n"); 503 return -EACCES; 504 } 505 if (t == DST_OP) 506 mark_reg_unknown_value(regs, regno); 507 } 508 return 0; 509 } 510 511 static int bpf_size_to_bytes(int bpf_size) 512 { 513 if (bpf_size == BPF_W) 514 return 4; 515 else if (bpf_size == BPF_H) 516 return 2; 517 else if (bpf_size == BPF_B) 518 return 1; 519 else if (bpf_size == BPF_DW) 520 return 8; 521 else 522 return -EINVAL; 523 } 524 525 static bool is_spillable_regtype(enum bpf_reg_type type) 526 { 527 switch (type) { 528 case PTR_TO_MAP_VALUE: 529 case PTR_TO_MAP_VALUE_OR_NULL: 530 case PTR_TO_STACK: 531 case PTR_TO_CTX: 532 case PTR_TO_PACKET: 533 case PTR_TO_PACKET_END: 534 case FRAME_PTR: 535 case CONST_PTR_TO_MAP: 536 return true; 537 default: 538 return false; 539 } 540 } 541 542 /* check_stack_read/write functions track spill/fill of registers, 543 * stack boundary and alignment are checked in check_mem_access() 544 */ 545 static int check_stack_write(struct bpf_verifier_state *state, int off, 546 int size, int value_regno) 547 { 548 int i; 549 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0, 550 * so it's aligned access and [off, off + size) are within stack limits 551 */ 552 553 if (value_regno >= 0 && 554 is_spillable_regtype(state->regs[value_regno].type)) { 555 556 /* register containing pointer is being spilled into stack */ 557 if (size != BPF_REG_SIZE) { 558 verbose("invalid size of register spill\n"); 559 return -EACCES; 560 } 561 562 /* save register state */ 563 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = 564 state->regs[value_regno]; 565 566 for (i = 0; i < BPF_REG_SIZE; i++) 567 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL; 568 } else { 569 /* regular write of data into stack */ 570 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = 571 (struct bpf_reg_state) {}; 572 573 for (i = 0; i < size; i++) 574 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC; 575 } 576 return 0; 577 } 578 579 static int check_stack_read(struct bpf_verifier_state *state, int off, int size, 580 int value_regno) 581 { 582 u8 *slot_type; 583 int i; 584 585 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off]; 586 587 if (slot_type[0] == STACK_SPILL) { 588 if (size != BPF_REG_SIZE) { 589 verbose("invalid size of register spill\n"); 590 return -EACCES; 591 } 592 for (i = 1; i < BPF_REG_SIZE; i++) { 593 if (slot_type[i] != STACK_SPILL) { 594 verbose("corrupted spill memory\n"); 595 return -EACCES; 596 } 597 } 598 599 if (value_regno >= 0) 600 /* restore register state from stack */ 601 state->regs[value_regno] = 602 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE]; 603 return 0; 604 } else { 605 for (i = 0; i < size; i++) { 606 if (slot_type[i] != STACK_MISC) { 607 verbose("invalid read from stack off %d+%d size %d\n", 608 off, i, size); 609 return -EACCES; 610 } 611 } 612 if (value_regno >= 0) 613 /* have read misc data from the stack */ 614 mark_reg_unknown_value(state->regs, value_regno); 615 return 0; 616 } 617 } 618 619 /* check read/write into map element returned by bpf_map_lookup_elem() */ 620 static int check_map_access(struct bpf_verifier_env *env, u32 regno, int off, 621 int size) 622 { 623 struct bpf_map *map = env->cur_state.regs[regno].map_ptr; 624 625 if (off < 0 || off + size > map->value_size) { 626 verbose("invalid access to map value, value_size=%d off=%d size=%d\n", 627 map->value_size, off, size); 628 return -EACCES; 629 } 630 return 0; 631 } 632 633 #define MAX_PACKET_OFF 0xffff 634 635 static bool may_access_direct_pkt_data(struct bpf_verifier_env *env, 636 const struct bpf_call_arg_meta *meta, 637 enum bpf_access_type t) 638 { 639 switch (env->prog->type) { 640 case BPF_PROG_TYPE_LWT_IN: 641 case BPF_PROG_TYPE_LWT_OUT: 642 /* dst_input() and dst_output() can't write for now */ 643 if (t == BPF_WRITE) 644 return false; 645 case BPF_PROG_TYPE_SCHED_CLS: 646 case BPF_PROG_TYPE_SCHED_ACT: 647 case BPF_PROG_TYPE_XDP: 648 case BPF_PROG_TYPE_LWT_XMIT: 649 if (meta) 650 return meta->pkt_access; 651 652 env->seen_direct_write = true; 653 return true; 654 default: 655 return false; 656 } 657 } 658 659 static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off, 660 int size) 661 { 662 struct bpf_reg_state *regs = env->cur_state.regs; 663 struct bpf_reg_state *reg = ®s[regno]; 664 665 off += reg->off; 666 if (off < 0 || size <= 0 || off + size > reg->range) { 667 verbose("invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n", 668 off, size, regno, reg->id, reg->off, reg->range); 669 return -EACCES; 670 } 671 return 0; 672 } 673 674 /* check access to 'struct bpf_context' fields */ 675 static int check_ctx_access(struct bpf_verifier_env *env, int off, int size, 676 enum bpf_access_type t, enum bpf_reg_type *reg_type) 677 { 678 /* for analyzer ctx accesses are already validated and converted */ 679 if (env->analyzer_ops) 680 return 0; 681 682 if (env->prog->aux->ops->is_valid_access && 683 env->prog->aux->ops->is_valid_access(off, size, t, reg_type)) { 684 /* remember the offset of last byte accessed in ctx */ 685 if (env->prog->aux->max_ctx_offset < off + size) 686 env->prog->aux->max_ctx_offset = off + size; 687 return 0; 688 } 689 690 verbose("invalid bpf_context access off=%d size=%d\n", off, size); 691 return -EACCES; 692 } 693 694 static bool is_pointer_value(struct bpf_verifier_env *env, int regno) 695 { 696 if (env->allow_ptr_leaks) 697 return false; 698 699 switch (env->cur_state.regs[regno].type) { 700 case UNKNOWN_VALUE: 701 case CONST_IMM: 702 return false; 703 default: 704 return true; 705 } 706 } 707 708 static int check_ptr_alignment(struct bpf_verifier_env *env, 709 struct bpf_reg_state *reg, int off, int size) 710 { 711 if (reg->type != PTR_TO_PACKET && reg->type != PTR_TO_MAP_VALUE_ADJ) { 712 if (off % size != 0) { 713 verbose("misaligned access off %d size %d\n", 714 off, size); 715 return -EACCES; 716 } else { 717 return 0; 718 } 719 } 720 721 if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) 722 /* misaligned access to packet is ok on x86,arm,arm64 */ 723 return 0; 724 725 if (reg->id && size != 1) { 726 verbose("Unknown packet alignment. Only byte-sized access allowed\n"); 727 return -EACCES; 728 } 729 730 /* skb->data is NET_IP_ALIGN-ed */ 731 if (reg->type == PTR_TO_PACKET && 732 (NET_IP_ALIGN + reg->off + off) % size != 0) { 733 verbose("misaligned packet access off %d+%d+%d size %d\n", 734 NET_IP_ALIGN, reg->off, off, size); 735 return -EACCES; 736 } 737 return 0; 738 } 739 740 /* check whether memory at (regno + off) is accessible for t = (read | write) 741 * if t==write, value_regno is a register which value is stored into memory 742 * if t==read, value_regno is a register which will receive the value from memory 743 * if t==write && value_regno==-1, some unknown value is stored into memory 744 * if t==read && value_regno==-1, don't care what we read from memory 745 */ 746 static int check_mem_access(struct bpf_verifier_env *env, u32 regno, int off, 747 int bpf_size, enum bpf_access_type t, 748 int value_regno) 749 { 750 struct bpf_verifier_state *state = &env->cur_state; 751 struct bpf_reg_state *reg = &state->regs[regno]; 752 int size, err = 0; 753 754 if (reg->type == PTR_TO_STACK) 755 off += reg->imm; 756 757 size = bpf_size_to_bytes(bpf_size); 758 if (size < 0) 759 return size; 760 761 err = check_ptr_alignment(env, reg, off, size); 762 if (err) 763 return err; 764 765 if (reg->type == PTR_TO_MAP_VALUE || 766 reg->type == PTR_TO_MAP_VALUE_ADJ) { 767 if (t == BPF_WRITE && value_regno >= 0 && 768 is_pointer_value(env, value_regno)) { 769 verbose("R%d leaks addr into map\n", value_regno); 770 return -EACCES; 771 } 772 773 /* If we adjusted the register to this map value at all then we 774 * need to change off and size to min_value and max_value 775 * respectively to make sure our theoretical access will be 776 * safe. 777 */ 778 if (reg->type == PTR_TO_MAP_VALUE_ADJ) { 779 if (log_level) 780 print_verifier_state(state); 781 env->varlen_map_value_access = true; 782 /* The minimum value is only important with signed 783 * comparisons where we can't assume the floor of a 784 * value is 0. If we are using signed variables for our 785 * index'es we need to make sure that whatever we use 786 * will have a set floor within our range. 787 */ 788 if (reg->min_value < 0) { 789 verbose("R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n", 790 regno); 791 return -EACCES; 792 } 793 err = check_map_access(env, regno, reg->min_value + off, 794 size); 795 if (err) { 796 verbose("R%d min value is outside of the array range\n", 797 regno); 798 return err; 799 } 800 801 /* If we haven't set a max value then we need to bail 802 * since we can't be sure we won't do bad things. 803 */ 804 if (reg->max_value == BPF_REGISTER_MAX_RANGE) { 805 verbose("R%d unbounded memory access, make sure to bounds check any array access into a map\n", 806 regno); 807 return -EACCES; 808 } 809 off += reg->max_value; 810 } 811 err = check_map_access(env, regno, off, size); 812 if (!err && t == BPF_READ && value_regno >= 0) 813 mark_reg_unknown_value(state->regs, value_regno); 814 815 } else if (reg->type == PTR_TO_CTX) { 816 enum bpf_reg_type reg_type = UNKNOWN_VALUE; 817 818 if (t == BPF_WRITE && value_regno >= 0 && 819 is_pointer_value(env, value_regno)) { 820 verbose("R%d leaks addr into ctx\n", value_regno); 821 return -EACCES; 822 } 823 err = check_ctx_access(env, off, size, t, ®_type); 824 if (!err && t == BPF_READ && value_regno >= 0) { 825 mark_reg_unknown_value(state->regs, value_regno); 826 /* note that reg.[id|off|range] == 0 */ 827 state->regs[value_regno].type = reg_type; 828 } 829 830 } else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) { 831 if (off >= 0 || off < -MAX_BPF_STACK) { 832 verbose("invalid stack off=%d size=%d\n", off, size); 833 return -EACCES; 834 } 835 if (t == BPF_WRITE) { 836 if (!env->allow_ptr_leaks && 837 state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL && 838 size != BPF_REG_SIZE) { 839 verbose("attempt to corrupt spilled pointer on stack\n"); 840 return -EACCES; 841 } 842 err = check_stack_write(state, off, size, value_regno); 843 } else { 844 err = check_stack_read(state, off, size, value_regno); 845 } 846 } else if (state->regs[regno].type == PTR_TO_PACKET) { 847 if (t == BPF_WRITE && !may_access_direct_pkt_data(env, NULL, t)) { 848 verbose("cannot write into packet\n"); 849 return -EACCES; 850 } 851 if (t == BPF_WRITE && value_regno >= 0 && 852 is_pointer_value(env, value_regno)) { 853 verbose("R%d leaks addr into packet\n", value_regno); 854 return -EACCES; 855 } 856 err = check_packet_access(env, regno, off, size); 857 if (!err && t == BPF_READ && value_regno >= 0) 858 mark_reg_unknown_value(state->regs, value_regno); 859 } else { 860 verbose("R%d invalid mem access '%s'\n", 861 regno, reg_type_str[reg->type]); 862 return -EACCES; 863 } 864 865 if (!err && size <= 2 && value_regno >= 0 && env->allow_ptr_leaks && 866 state->regs[value_regno].type == UNKNOWN_VALUE) { 867 /* 1 or 2 byte load zero-extends, determine the number of 868 * zero upper bits. Not doing it fo 4 byte load, since 869 * such values cannot be added to ptr_to_packet anyway. 870 */ 871 state->regs[value_regno].imm = 64 - size * 8; 872 } 873 return err; 874 } 875 876 static int check_xadd(struct bpf_verifier_env *env, struct bpf_insn *insn) 877 { 878 struct bpf_reg_state *regs = env->cur_state.regs; 879 int err; 880 881 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) || 882 insn->imm != 0) { 883 verbose("BPF_XADD uses reserved fields\n"); 884 return -EINVAL; 885 } 886 887 /* check src1 operand */ 888 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 889 if (err) 890 return err; 891 892 /* check src2 operand */ 893 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 894 if (err) 895 return err; 896 897 /* check whether atomic_add can read the memory */ 898 err = check_mem_access(env, insn->dst_reg, insn->off, 899 BPF_SIZE(insn->code), BPF_READ, -1); 900 if (err) 901 return err; 902 903 /* check whether atomic_add can write into the same memory */ 904 return check_mem_access(env, insn->dst_reg, insn->off, 905 BPF_SIZE(insn->code), BPF_WRITE, -1); 906 } 907 908 /* when register 'regno' is passed into function that will read 'access_size' 909 * bytes from that pointer, make sure that it's within stack boundary 910 * and all elements of stack are initialized 911 */ 912 static int check_stack_boundary(struct bpf_verifier_env *env, int regno, 913 int access_size, bool zero_size_allowed, 914 struct bpf_call_arg_meta *meta) 915 { 916 struct bpf_verifier_state *state = &env->cur_state; 917 struct bpf_reg_state *regs = state->regs; 918 int off, i; 919 920 if (regs[regno].type != PTR_TO_STACK) { 921 if (zero_size_allowed && access_size == 0 && 922 regs[regno].type == CONST_IMM && 923 regs[regno].imm == 0) 924 return 0; 925 926 verbose("R%d type=%s expected=%s\n", regno, 927 reg_type_str[regs[regno].type], 928 reg_type_str[PTR_TO_STACK]); 929 return -EACCES; 930 } 931 932 off = regs[regno].imm; 933 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 || 934 access_size <= 0) { 935 verbose("invalid stack type R%d off=%d access_size=%d\n", 936 regno, off, access_size); 937 return -EACCES; 938 } 939 940 if (meta && meta->raw_mode) { 941 meta->access_size = access_size; 942 meta->regno = regno; 943 return 0; 944 } 945 946 for (i = 0; i < access_size; i++) { 947 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) { 948 verbose("invalid indirect read from stack off %d+%d size %d\n", 949 off, i, access_size); 950 return -EACCES; 951 } 952 } 953 return 0; 954 } 955 956 static int check_func_arg(struct bpf_verifier_env *env, u32 regno, 957 enum bpf_arg_type arg_type, 958 struct bpf_call_arg_meta *meta) 959 { 960 struct bpf_reg_state *regs = env->cur_state.regs, *reg = ®s[regno]; 961 enum bpf_reg_type expected_type, type = reg->type; 962 int err = 0; 963 964 if (arg_type == ARG_DONTCARE) 965 return 0; 966 967 if (type == NOT_INIT) { 968 verbose("R%d !read_ok\n", regno); 969 return -EACCES; 970 } 971 972 if (arg_type == ARG_ANYTHING) { 973 if (is_pointer_value(env, regno)) { 974 verbose("R%d leaks addr into helper function\n", regno); 975 return -EACCES; 976 } 977 return 0; 978 } 979 980 if (type == PTR_TO_PACKET && 981 !may_access_direct_pkt_data(env, meta, BPF_READ)) { 982 verbose("helper access to the packet is not allowed\n"); 983 return -EACCES; 984 } 985 986 if (arg_type == ARG_PTR_TO_MAP_KEY || 987 arg_type == ARG_PTR_TO_MAP_VALUE) { 988 expected_type = PTR_TO_STACK; 989 if (type != PTR_TO_PACKET && type != expected_type) 990 goto err_type; 991 } else if (arg_type == ARG_CONST_STACK_SIZE || 992 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) { 993 expected_type = CONST_IMM; 994 if (type != expected_type) 995 goto err_type; 996 } else if (arg_type == ARG_CONST_MAP_PTR) { 997 expected_type = CONST_PTR_TO_MAP; 998 if (type != expected_type) 999 goto err_type; 1000 } else if (arg_type == ARG_PTR_TO_CTX) { 1001 expected_type = PTR_TO_CTX; 1002 if (type != expected_type) 1003 goto err_type; 1004 } else if (arg_type == ARG_PTR_TO_STACK || 1005 arg_type == ARG_PTR_TO_RAW_STACK) { 1006 expected_type = PTR_TO_STACK; 1007 /* One exception here. In case function allows for NULL to be 1008 * passed in as argument, it's a CONST_IMM type. Final test 1009 * happens during stack boundary checking. 1010 */ 1011 if (type == CONST_IMM && reg->imm == 0) 1012 /* final test in check_stack_boundary() */; 1013 else if (type != PTR_TO_PACKET && type != expected_type) 1014 goto err_type; 1015 meta->raw_mode = arg_type == ARG_PTR_TO_RAW_STACK; 1016 } else { 1017 verbose("unsupported arg_type %d\n", arg_type); 1018 return -EFAULT; 1019 } 1020 1021 if (arg_type == ARG_CONST_MAP_PTR) { 1022 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */ 1023 meta->map_ptr = reg->map_ptr; 1024 } else if (arg_type == ARG_PTR_TO_MAP_KEY) { 1025 /* bpf_map_xxx(..., map_ptr, ..., key) call: 1026 * check that [key, key + map->key_size) are within 1027 * stack limits and initialized 1028 */ 1029 if (!meta->map_ptr) { 1030 /* in function declaration map_ptr must come before 1031 * map_key, so that it's verified and known before 1032 * we have to check map_key here. Otherwise it means 1033 * that kernel subsystem misconfigured verifier 1034 */ 1035 verbose("invalid map_ptr to access map->key\n"); 1036 return -EACCES; 1037 } 1038 if (type == PTR_TO_PACKET) 1039 err = check_packet_access(env, regno, 0, 1040 meta->map_ptr->key_size); 1041 else 1042 err = check_stack_boundary(env, regno, 1043 meta->map_ptr->key_size, 1044 false, NULL); 1045 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) { 1046 /* bpf_map_xxx(..., map_ptr, ..., value) call: 1047 * check [value, value + map->value_size) validity 1048 */ 1049 if (!meta->map_ptr) { 1050 /* kernel subsystem misconfigured verifier */ 1051 verbose("invalid map_ptr to access map->value\n"); 1052 return -EACCES; 1053 } 1054 if (type == PTR_TO_PACKET) 1055 err = check_packet_access(env, regno, 0, 1056 meta->map_ptr->value_size); 1057 else 1058 err = check_stack_boundary(env, regno, 1059 meta->map_ptr->value_size, 1060 false, NULL); 1061 } else if (arg_type == ARG_CONST_STACK_SIZE || 1062 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) { 1063 bool zero_size_allowed = (arg_type == ARG_CONST_STACK_SIZE_OR_ZERO); 1064 1065 /* bpf_xxx(..., buf, len) call will access 'len' bytes 1066 * from stack pointer 'buf'. Check it 1067 * note: regno == len, regno - 1 == buf 1068 */ 1069 if (regno == 0) { 1070 /* kernel subsystem misconfigured verifier */ 1071 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n"); 1072 return -EACCES; 1073 } 1074 if (regs[regno - 1].type == PTR_TO_PACKET) 1075 err = check_packet_access(env, regno - 1, 0, reg->imm); 1076 else 1077 err = check_stack_boundary(env, regno - 1, reg->imm, 1078 zero_size_allowed, meta); 1079 } 1080 1081 return err; 1082 err_type: 1083 verbose("R%d type=%s expected=%s\n", regno, 1084 reg_type_str[type], reg_type_str[expected_type]); 1085 return -EACCES; 1086 } 1087 1088 static int check_map_func_compatibility(struct bpf_map *map, int func_id) 1089 { 1090 if (!map) 1091 return 0; 1092 1093 /* We need a two way check, first is from map perspective ... */ 1094 switch (map->map_type) { 1095 case BPF_MAP_TYPE_PROG_ARRAY: 1096 if (func_id != BPF_FUNC_tail_call) 1097 goto error; 1098 break; 1099 case BPF_MAP_TYPE_PERF_EVENT_ARRAY: 1100 if (func_id != BPF_FUNC_perf_event_read && 1101 func_id != BPF_FUNC_perf_event_output) 1102 goto error; 1103 break; 1104 case BPF_MAP_TYPE_STACK_TRACE: 1105 if (func_id != BPF_FUNC_get_stackid) 1106 goto error; 1107 break; 1108 case BPF_MAP_TYPE_CGROUP_ARRAY: 1109 if (func_id != BPF_FUNC_skb_under_cgroup && 1110 func_id != BPF_FUNC_current_task_under_cgroup) 1111 goto error; 1112 break; 1113 default: 1114 break; 1115 } 1116 1117 /* ... and second from the function itself. */ 1118 switch (func_id) { 1119 case BPF_FUNC_tail_call: 1120 if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY) 1121 goto error; 1122 break; 1123 case BPF_FUNC_perf_event_read: 1124 case BPF_FUNC_perf_event_output: 1125 if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY) 1126 goto error; 1127 break; 1128 case BPF_FUNC_get_stackid: 1129 if (map->map_type != BPF_MAP_TYPE_STACK_TRACE) 1130 goto error; 1131 break; 1132 case BPF_FUNC_current_task_under_cgroup: 1133 case BPF_FUNC_skb_under_cgroup: 1134 if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY) 1135 goto error; 1136 break; 1137 default: 1138 break; 1139 } 1140 1141 return 0; 1142 error: 1143 verbose("cannot pass map_type %d into func %s#%d\n", 1144 map->map_type, func_id_name(func_id), func_id); 1145 return -EINVAL; 1146 } 1147 1148 static int check_raw_mode(const struct bpf_func_proto *fn) 1149 { 1150 int count = 0; 1151 1152 if (fn->arg1_type == ARG_PTR_TO_RAW_STACK) 1153 count++; 1154 if (fn->arg2_type == ARG_PTR_TO_RAW_STACK) 1155 count++; 1156 if (fn->arg3_type == ARG_PTR_TO_RAW_STACK) 1157 count++; 1158 if (fn->arg4_type == ARG_PTR_TO_RAW_STACK) 1159 count++; 1160 if (fn->arg5_type == ARG_PTR_TO_RAW_STACK) 1161 count++; 1162 1163 return count > 1 ? -EINVAL : 0; 1164 } 1165 1166 static void clear_all_pkt_pointers(struct bpf_verifier_env *env) 1167 { 1168 struct bpf_verifier_state *state = &env->cur_state; 1169 struct bpf_reg_state *regs = state->regs, *reg; 1170 int i; 1171 1172 for (i = 0; i < MAX_BPF_REG; i++) 1173 if (regs[i].type == PTR_TO_PACKET || 1174 regs[i].type == PTR_TO_PACKET_END) 1175 mark_reg_unknown_value(regs, i); 1176 1177 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 1178 if (state->stack_slot_type[i] != STACK_SPILL) 1179 continue; 1180 reg = &state->spilled_regs[i / BPF_REG_SIZE]; 1181 if (reg->type != PTR_TO_PACKET && 1182 reg->type != PTR_TO_PACKET_END) 1183 continue; 1184 reg->type = UNKNOWN_VALUE; 1185 reg->imm = 0; 1186 } 1187 } 1188 1189 static int check_call(struct bpf_verifier_env *env, int func_id) 1190 { 1191 struct bpf_verifier_state *state = &env->cur_state; 1192 const struct bpf_func_proto *fn = NULL; 1193 struct bpf_reg_state *regs = state->regs; 1194 struct bpf_reg_state *reg; 1195 struct bpf_call_arg_meta meta; 1196 bool changes_data; 1197 int i, err; 1198 1199 /* find function prototype */ 1200 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) { 1201 verbose("invalid func %s#%d\n", func_id_name(func_id), func_id); 1202 return -EINVAL; 1203 } 1204 1205 if (env->prog->aux->ops->get_func_proto) 1206 fn = env->prog->aux->ops->get_func_proto(func_id); 1207 1208 if (!fn) { 1209 verbose("unknown func %s#%d\n", func_id_name(func_id), func_id); 1210 return -EINVAL; 1211 } 1212 1213 /* eBPF programs must be GPL compatible to use GPL-ed functions */ 1214 if (!env->prog->gpl_compatible && fn->gpl_only) { 1215 verbose("cannot call GPL only function from proprietary program\n"); 1216 return -EINVAL; 1217 } 1218 1219 changes_data = bpf_helper_changes_skb_data(fn->func); 1220 1221 memset(&meta, 0, sizeof(meta)); 1222 meta.pkt_access = fn->pkt_access; 1223 1224 /* We only support one arg being in raw mode at the moment, which 1225 * is sufficient for the helper functions we have right now. 1226 */ 1227 err = check_raw_mode(fn); 1228 if (err) { 1229 verbose("kernel subsystem misconfigured func %s#%d\n", 1230 func_id_name(func_id), func_id); 1231 return err; 1232 } 1233 1234 /* check args */ 1235 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta); 1236 if (err) 1237 return err; 1238 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta); 1239 if (err) 1240 return err; 1241 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta); 1242 if (err) 1243 return err; 1244 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta); 1245 if (err) 1246 return err; 1247 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta); 1248 if (err) 1249 return err; 1250 1251 /* Mark slots with STACK_MISC in case of raw mode, stack offset 1252 * is inferred from register state. 1253 */ 1254 for (i = 0; i < meta.access_size; i++) { 1255 err = check_mem_access(env, meta.regno, i, BPF_B, BPF_WRITE, -1); 1256 if (err) 1257 return err; 1258 } 1259 1260 /* reset caller saved regs */ 1261 for (i = 0; i < CALLER_SAVED_REGS; i++) { 1262 reg = regs + caller_saved[i]; 1263 reg->type = NOT_INIT; 1264 reg->imm = 0; 1265 } 1266 1267 /* update return register */ 1268 if (fn->ret_type == RET_INTEGER) { 1269 regs[BPF_REG_0].type = UNKNOWN_VALUE; 1270 } else if (fn->ret_type == RET_VOID) { 1271 regs[BPF_REG_0].type = NOT_INIT; 1272 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) { 1273 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL; 1274 regs[BPF_REG_0].max_value = regs[BPF_REG_0].min_value = 0; 1275 /* remember map_ptr, so that check_map_access() 1276 * can check 'value_size' boundary of memory access 1277 * to map element returned from bpf_map_lookup_elem() 1278 */ 1279 if (meta.map_ptr == NULL) { 1280 verbose("kernel subsystem misconfigured verifier\n"); 1281 return -EINVAL; 1282 } 1283 regs[BPF_REG_0].map_ptr = meta.map_ptr; 1284 regs[BPF_REG_0].id = ++env->id_gen; 1285 } else { 1286 verbose("unknown return type %d of func %s#%d\n", 1287 fn->ret_type, func_id_name(func_id), func_id); 1288 return -EINVAL; 1289 } 1290 1291 err = check_map_func_compatibility(meta.map_ptr, func_id); 1292 if (err) 1293 return err; 1294 1295 if (changes_data) 1296 clear_all_pkt_pointers(env); 1297 return 0; 1298 } 1299 1300 static int check_packet_ptr_add(struct bpf_verifier_env *env, 1301 struct bpf_insn *insn) 1302 { 1303 struct bpf_reg_state *regs = env->cur_state.regs; 1304 struct bpf_reg_state *dst_reg = ®s[insn->dst_reg]; 1305 struct bpf_reg_state *src_reg = ®s[insn->src_reg]; 1306 struct bpf_reg_state tmp_reg; 1307 s32 imm; 1308 1309 if (BPF_SRC(insn->code) == BPF_K) { 1310 /* pkt_ptr += imm */ 1311 imm = insn->imm; 1312 1313 add_imm: 1314 if (imm <= 0) { 1315 verbose("addition of negative constant to packet pointer is not allowed\n"); 1316 return -EACCES; 1317 } 1318 if (imm >= MAX_PACKET_OFF || 1319 imm + dst_reg->off >= MAX_PACKET_OFF) { 1320 verbose("constant %d is too large to add to packet pointer\n", 1321 imm); 1322 return -EACCES; 1323 } 1324 /* a constant was added to pkt_ptr. 1325 * Remember it while keeping the same 'id' 1326 */ 1327 dst_reg->off += imm; 1328 } else { 1329 if (src_reg->type == PTR_TO_PACKET) { 1330 /* R6=pkt(id=0,off=0,r=62) R7=imm22; r7 += r6 */ 1331 tmp_reg = *dst_reg; /* save r7 state */ 1332 *dst_reg = *src_reg; /* copy pkt_ptr state r6 into r7 */ 1333 src_reg = &tmp_reg; /* pretend it's src_reg state */ 1334 /* if the checks below reject it, the copy won't matter, 1335 * since we're rejecting the whole program. If all ok, 1336 * then imm22 state will be added to r7 1337 * and r7 will be pkt(id=0,off=22,r=62) while 1338 * r6 will stay as pkt(id=0,off=0,r=62) 1339 */ 1340 } 1341 1342 if (src_reg->type == CONST_IMM) { 1343 /* pkt_ptr += reg where reg is known constant */ 1344 imm = src_reg->imm; 1345 goto add_imm; 1346 } 1347 /* disallow pkt_ptr += reg 1348 * if reg is not uknown_value with guaranteed zero upper bits 1349 * otherwise pkt_ptr may overflow and addition will become 1350 * subtraction which is not allowed 1351 */ 1352 if (src_reg->type != UNKNOWN_VALUE) { 1353 verbose("cannot add '%s' to ptr_to_packet\n", 1354 reg_type_str[src_reg->type]); 1355 return -EACCES; 1356 } 1357 if (src_reg->imm < 48) { 1358 verbose("cannot add integer value with %lld upper zero bits to ptr_to_packet\n", 1359 src_reg->imm); 1360 return -EACCES; 1361 } 1362 /* dst_reg stays as pkt_ptr type and since some positive 1363 * integer value was added to the pointer, increment its 'id' 1364 */ 1365 dst_reg->id = ++env->id_gen; 1366 1367 /* something was added to pkt_ptr, set range and off to zero */ 1368 dst_reg->off = 0; 1369 dst_reg->range = 0; 1370 } 1371 return 0; 1372 } 1373 1374 static int evaluate_reg_alu(struct bpf_verifier_env *env, struct bpf_insn *insn) 1375 { 1376 struct bpf_reg_state *regs = env->cur_state.regs; 1377 struct bpf_reg_state *dst_reg = ®s[insn->dst_reg]; 1378 u8 opcode = BPF_OP(insn->code); 1379 s64 imm_log2; 1380 1381 /* for type == UNKNOWN_VALUE: 1382 * imm > 0 -> number of zero upper bits 1383 * imm == 0 -> don't track which is the same as all bits can be non-zero 1384 */ 1385 1386 if (BPF_SRC(insn->code) == BPF_X) { 1387 struct bpf_reg_state *src_reg = ®s[insn->src_reg]; 1388 1389 if (src_reg->type == UNKNOWN_VALUE && src_reg->imm > 0 && 1390 dst_reg->imm && opcode == BPF_ADD) { 1391 /* dreg += sreg 1392 * where both have zero upper bits. Adding them 1393 * can only result making one more bit non-zero 1394 * in the larger value. 1395 * Ex. 0xffff (imm=48) + 1 (imm=63) = 0x10000 (imm=47) 1396 * 0xffff (imm=48) + 0xffff = 0x1fffe (imm=47) 1397 */ 1398 dst_reg->imm = min(dst_reg->imm, src_reg->imm); 1399 dst_reg->imm--; 1400 return 0; 1401 } 1402 if (src_reg->type == CONST_IMM && src_reg->imm > 0 && 1403 dst_reg->imm && opcode == BPF_ADD) { 1404 /* dreg += sreg 1405 * where dreg has zero upper bits and sreg is const. 1406 * Adding them can only result making one more bit 1407 * non-zero in the larger value. 1408 */ 1409 imm_log2 = __ilog2_u64((long long)src_reg->imm); 1410 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2); 1411 dst_reg->imm--; 1412 return 0; 1413 } 1414 /* all other cases non supported yet, just mark dst_reg */ 1415 dst_reg->imm = 0; 1416 return 0; 1417 } 1418 1419 /* sign extend 32-bit imm into 64-bit to make sure that 1420 * negative values occupy bit 63. Note ilog2() would have 1421 * been incorrect, since sizeof(insn->imm) == 4 1422 */ 1423 imm_log2 = __ilog2_u64((long long)insn->imm); 1424 1425 if (dst_reg->imm && opcode == BPF_LSH) { 1426 /* reg <<= imm 1427 * if reg was a result of 2 byte load, then its imm == 48 1428 * which means that upper 48 bits are zero and shifting this reg 1429 * left by 4 would mean that upper 44 bits are still zero 1430 */ 1431 dst_reg->imm -= insn->imm; 1432 } else if (dst_reg->imm && opcode == BPF_MUL) { 1433 /* reg *= imm 1434 * if multiplying by 14 subtract 4 1435 * This is conservative calculation of upper zero bits. 1436 * It's not trying to special case insn->imm == 1 or 0 cases 1437 */ 1438 dst_reg->imm -= imm_log2 + 1; 1439 } else if (opcode == BPF_AND) { 1440 /* reg &= imm */ 1441 dst_reg->imm = 63 - imm_log2; 1442 } else if (dst_reg->imm && opcode == BPF_ADD) { 1443 /* reg += imm */ 1444 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2); 1445 dst_reg->imm--; 1446 } else if (opcode == BPF_RSH) { 1447 /* reg >>= imm 1448 * which means that after right shift, upper bits will be zero 1449 * note that verifier already checked that 1450 * 0 <= imm < 64 for shift insn 1451 */ 1452 dst_reg->imm += insn->imm; 1453 if (unlikely(dst_reg->imm > 64)) 1454 /* some dumb code did: 1455 * r2 = *(u32 *)mem; 1456 * r2 >>= 32; 1457 * and all bits are zero now */ 1458 dst_reg->imm = 64; 1459 } else { 1460 /* all other alu ops, means that we don't know what will 1461 * happen to the value, mark it with unknown number of zero bits 1462 */ 1463 dst_reg->imm = 0; 1464 } 1465 1466 if (dst_reg->imm < 0) { 1467 /* all 64 bits of the register can contain non-zero bits 1468 * and such value cannot be added to ptr_to_packet, since it 1469 * may overflow, mark it as unknown to avoid further eval 1470 */ 1471 dst_reg->imm = 0; 1472 } 1473 return 0; 1474 } 1475 1476 static int evaluate_reg_imm_alu(struct bpf_verifier_env *env, 1477 struct bpf_insn *insn) 1478 { 1479 struct bpf_reg_state *regs = env->cur_state.regs; 1480 struct bpf_reg_state *dst_reg = ®s[insn->dst_reg]; 1481 struct bpf_reg_state *src_reg = ®s[insn->src_reg]; 1482 u8 opcode = BPF_OP(insn->code); 1483 1484 /* dst_reg->type == CONST_IMM here, simulate execution of 'add' insn. 1485 * Don't care about overflow or negative values, just add them 1486 */ 1487 if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_K) 1488 dst_reg->imm += insn->imm; 1489 else if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_X && 1490 src_reg->type == CONST_IMM) 1491 dst_reg->imm += src_reg->imm; 1492 else 1493 mark_reg_unknown_value(regs, insn->dst_reg); 1494 return 0; 1495 } 1496 1497 static void check_reg_overflow(struct bpf_reg_state *reg) 1498 { 1499 if (reg->max_value > BPF_REGISTER_MAX_RANGE) 1500 reg->max_value = BPF_REGISTER_MAX_RANGE; 1501 if (reg->min_value < BPF_REGISTER_MIN_RANGE || 1502 reg->min_value > BPF_REGISTER_MAX_RANGE) 1503 reg->min_value = BPF_REGISTER_MIN_RANGE; 1504 } 1505 1506 static void adjust_reg_min_max_vals(struct bpf_verifier_env *env, 1507 struct bpf_insn *insn) 1508 { 1509 struct bpf_reg_state *regs = env->cur_state.regs, *dst_reg; 1510 s64 min_val = BPF_REGISTER_MIN_RANGE; 1511 u64 max_val = BPF_REGISTER_MAX_RANGE; 1512 u8 opcode = BPF_OP(insn->code); 1513 1514 dst_reg = ®s[insn->dst_reg]; 1515 if (BPF_SRC(insn->code) == BPF_X) { 1516 check_reg_overflow(®s[insn->src_reg]); 1517 min_val = regs[insn->src_reg].min_value; 1518 max_val = regs[insn->src_reg].max_value; 1519 1520 /* If the source register is a random pointer then the 1521 * min_value/max_value values represent the range of the known 1522 * accesses into that value, not the actual min/max value of the 1523 * register itself. In this case we have to reset the reg range 1524 * values so we know it is not safe to look at. 1525 */ 1526 if (regs[insn->src_reg].type != CONST_IMM && 1527 regs[insn->src_reg].type != UNKNOWN_VALUE) { 1528 min_val = BPF_REGISTER_MIN_RANGE; 1529 max_val = BPF_REGISTER_MAX_RANGE; 1530 } 1531 } else if (insn->imm < BPF_REGISTER_MAX_RANGE && 1532 (s64)insn->imm > BPF_REGISTER_MIN_RANGE) { 1533 min_val = max_val = insn->imm; 1534 } 1535 1536 /* We don't know anything about what was done to this register, mark it 1537 * as unknown. 1538 */ 1539 if (min_val == BPF_REGISTER_MIN_RANGE && 1540 max_val == BPF_REGISTER_MAX_RANGE) { 1541 reset_reg_range_values(regs, insn->dst_reg); 1542 return; 1543 } 1544 1545 /* If one of our values was at the end of our ranges then we can't just 1546 * do our normal operations to the register, we need to set the values 1547 * to the min/max since they are undefined. 1548 */ 1549 if (min_val == BPF_REGISTER_MIN_RANGE) 1550 dst_reg->min_value = BPF_REGISTER_MIN_RANGE; 1551 if (max_val == BPF_REGISTER_MAX_RANGE) 1552 dst_reg->max_value = BPF_REGISTER_MAX_RANGE; 1553 1554 switch (opcode) { 1555 case BPF_ADD: 1556 if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) 1557 dst_reg->min_value += min_val; 1558 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1559 dst_reg->max_value += max_val; 1560 break; 1561 case BPF_SUB: 1562 if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) 1563 dst_reg->min_value -= min_val; 1564 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1565 dst_reg->max_value -= max_val; 1566 break; 1567 case BPF_MUL: 1568 if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) 1569 dst_reg->min_value *= min_val; 1570 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1571 dst_reg->max_value *= max_val; 1572 break; 1573 case BPF_AND: 1574 /* Disallow AND'ing of negative numbers, ain't nobody got time 1575 * for that. Otherwise the minimum is 0 and the max is the max 1576 * value we could AND against. 1577 */ 1578 if (min_val < 0) 1579 dst_reg->min_value = BPF_REGISTER_MIN_RANGE; 1580 else 1581 dst_reg->min_value = 0; 1582 dst_reg->max_value = max_val; 1583 break; 1584 case BPF_LSH: 1585 /* Gotta have special overflow logic here, if we're shifting 1586 * more than MAX_RANGE then just assume we have an invalid 1587 * range. 1588 */ 1589 if (min_val > ilog2(BPF_REGISTER_MAX_RANGE)) 1590 dst_reg->min_value = BPF_REGISTER_MIN_RANGE; 1591 else if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE) 1592 dst_reg->min_value <<= min_val; 1593 1594 if (max_val > ilog2(BPF_REGISTER_MAX_RANGE)) 1595 dst_reg->max_value = BPF_REGISTER_MAX_RANGE; 1596 else if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1597 dst_reg->max_value <<= max_val; 1598 break; 1599 case BPF_RSH: 1600 /* RSH by a negative number is undefined, and the BPF_RSH is an 1601 * unsigned shift, so make the appropriate casts. 1602 */ 1603 if (min_val < 0 || dst_reg->min_value < 0) 1604 dst_reg->min_value = BPF_REGISTER_MIN_RANGE; 1605 else 1606 dst_reg->min_value = 1607 (u64)(dst_reg->min_value) >> min_val; 1608 if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE) 1609 dst_reg->max_value >>= max_val; 1610 break; 1611 default: 1612 reset_reg_range_values(regs, insn->dst_reg); 1613 break; 1614 } 1615 1616 check_reg_overflow(dst_reg); 1617 } 1618 1619 /* check validity of 32-bit and 64-bit arithmetic operations */ 1620 static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn) 1621 { 1622 struct bpf_reg_state *regs = env->cur_state.regs, *dst_reg; 1623 u8 opcode = BPF_OP(insn->code); 1624 int err; 1625 1626 if (opcode == BPF_END || opcode == BPF_NEG) { 1627 if (opcode == BPF_NEG) { 1628 if (BPF_SRC(insn->code) != 0 || 1629 insn->src_reg != BPF_REG_0 || 1630 insn->off != 0 || insn->imm != 0) { 1631 verbose("BPF_NEG uses reserved fields\n"); 1632 return -EINVAL; 1633 } 1634 } else { 1635 if (insn->src_reg != BPF_REG_0 || insn->off != 0 || 1636 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) { 1637 verbose("BPF_END uses reserved fields\n"); 1638 return -EINVAL; 1639 } 1640 } 1641 1642 /* check src operand */ 1643 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1644 if (err) 1645 return err; 1646 1647 if (is_pointer_value(env, insn->dst_reg)) { 1648 verbose("R%d pointer arithmetic prohibited\n", 1649 insn->dst_reg); 1650 return -EACCES; 1651 } 1652 1653 /* check dest operand */ 1654 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1655 if (err) 1656 return err; 1657 1658 } else if (opcode == BPF_MOV) { 1659 1660 if (BPF_SRC(insn->code) == BPF_X) { 1661 if (insn->imm != 0 || insn->off != 0) { 1662 verbose("BPF_MOV uses reserved fields\n"); 1663 return -EINVAL; 1664 } 1665 1666 /* check src operand */ 1667 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1668 if (err) 1669 return err; 1670 } else { 1671 if (insn->src_reg != BPF_REG_0 || insn->off != 0) { 1672 verbose("BPF_MOV uses reserved fields\n"); 1673 return -EINVAL; 1674 } 1675 } 1676 1677 /* check dest operand */ 1678 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1679 if (err) 1680 return err; 1681 1682 /* we are setting our register to something new, we need to 1683 * reset its range values. 1684 */ 1685 reset_reg_range_values(regs, insn->dst_reg); 1686 1687 if (BPF_SRC(insn->code) == BPF_X) { 1688 if (BPF_CLASS(insn->code) == BPF_ALU64) { 1689 /* case: R1 = R2 1690 * copy register state to dest reg 1691 */ 1692 regs[insn->dst_reg] = regs[insn->src_reg]; 1693 } else { 1694 if (is_pointer_value(env, insn->src_reg)) { 1695 verbose("R%d partial copy of pointer\n", 1696 insn->src_reg); 1697 return -EACCES; 1698 } 1699 mark_reg_unknown_value(regs, insn->dst_reg); 1700 } 1701 } else { 1702 /* case: R = imm 1703 * remember the value we stored into this reg 1704 */ 1705 regs[insn->dst_reg].type = CONST_IMM; 1706 regs[insn->dst_reg].imm = insn->imm; 1707 regs[insn->dst_reg].max_value = insn->imm; 1708 regs[insn->dst_reg].min_value = insn->imm; 1709 } 1710 1711 } else if (opcode > BPF_END) { 1712 verbose("invalid BPF_ALU opcode %x\n", opcode); 1713 return -EINVAL; 1714 1715 } else { /* all other ALU ops: and, sub, xor, add, ... */ 1716 1717 if (BPF_SRC(insn->code) == BPF_X) { 1718 if (insn->imm != 0 || insn->off != 0) { 1719 verbose("BPF_ALU uses reserved fields\n"); 1720 return -EINVAL; 1721 } 1722 /* check src1 operand */ 1723 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1724 if (err) 1725 return err; 1726 } else { 1727 if (insn->src_reg != BPF_REG_0 || insn->off != 0) { 1728 verbose("BPF_ALU uses reserved fields\n"); 1729 return -EINVAL; 1730 } 1731 } 1732 1733 /* check src2 operand */ 1734 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1735 if (err) 1736 return err; 1737 1738 if ((opcode == BPF_MOD || opcode == BPF_DIV) && 1739 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) { 1740 verbose("div by zero\n"); 1741 return -EINVAL; 1742 } 1743 1744 if ((opcode == BPF_LSH || opcode == BPF_RSH || 1745 opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) { 1746 int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32; 1747 1748 if (insn->imm < 0 || insn->imm >= size) { 1749 verbose("invalid shift %d\n", insn->imm); 1750 return -EINVAL; 1751 } 1752 } 1753 1754 /* check dest operand */ 1755 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); 1756 if (err) 1757 return err; 1758 1759 dst_reg = ®s[insn->dst_reg]; 1760 1761 /* first we want to adjust our ranges. */ 1762 adjust_reg_min_max_vals(env, insn); 1763 1764 /* pattern match 'bpf_add Rx, imm' instruction */ 1765 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 && 1766 dst_reg->type == FRAME_PTR && BPF_SRC(insn->code) == BPF_K) { 1767 dst_reg->type = PTR_TO_STACK; 1768 dst_reg->imm = insn->imm; 1769 return 0; 1770 } else if (opcode == BPF_ADD && 1771 BPF_CLASS(insn->code) == BPF_ALU64 && 1772 (dst_reg->type == PTR_TO_PACKET || 1773 (BPF_SRC(insn->code) == BPF_X && 1774 regs[insn->src_reg].type == PTR_TO_PACKET))) { 1775 /* ptr_to_packet += K|X */ 1776 return check_packet_ptr_add(env, insn); 1777 } else if (BPF_CLASS(insn->code) == BPF_ALU64 && 1778 dst_reg->type == UNKNOWN_VALUE && 1779 env->allow_ptr_leaks) { 1780 /* unknown += K|X */ 1781 return evaluate_reg_alu(env, insn); 1782 } else if (BPF_CLASS(insn->code) == BPF_ALU64 && 1783 dst_reg->type == CONST_IMM && 1784 env->allow_ptr_leaks) { 1785 /* reg_imm += K|X */ 1786 return evaluate_reg_imm_alu(env, insn); 1787 } else if (is_pointer_value(env, insn->dst_reg)) { 1788 verbose("R%d pointer arithmetic prohibited\n", 1789 insn->dst_reg); 1790 return -EACCES; 1791 } else if (BPF_SRC(insn->code) == BPF_X && 1792 is_pointer_value(env, insn->src_reg)) { 1793 verbose("R%d pointer arithmetic prohibited\n", 1794 insn->src_reg); 1795 return -EACCES; 1796 } 1797 1798 /* If we did pointer math on a map value then just set it to our 1799 * PTR_TO_MAP_VALUE_ADJ type so we can deal with any stores or 1800 * loads to this register appropriately, otherwise just mark the 1801 * register as unknown. 1802 */ 1803 if (env->allow_ptr_leaks && 1804 (dst_reg->type == PTR_TO_MAP_VALUE || 1805 dst_reg->type == PTR_TO_MAP_VALUE_ADJ)) 1806 dst_reg->type = PTR_TO_MAP_VALUE_ADJ; 1807 else 1808 mark_reg_unknown_value(regs, insn->dst_reg); 1809 } 1810 1811 return 0; 1812 } 1813 1814 static void find_good_pkt_pointers(struct bpf_verifier_state *state, 1815 struct bpf_reg_state *dst_reg) 1816 { 1817 struct bpf_reg_state *regs = state->regs, *reg; 1818 int i; 1819 1820 /* LLVM can generate two kind of checks: 1821 * 1822 * Type 1: 1823 * 1824 * r2 = r3; 1825 * r2 += 8; 1826 * if (r2 > pkt_end) goto <handle exception> 1827 * <access okay> 1828 * 1829 * Where: 1830 * r2 == dst_reg, pkt_end == src_reg 1831 * r2=pkt(id=n,off=8,r=0) 1832 * r3=pkt(id=n,off=0,r=0) 1833 * 1834 * Type 2: 1835 * 1836 * r2 = r3; 1837 * r2 += 8; 1838 * if (pkt_end >= r2) goto <access okay> 1839 * <handle exception> 1840 * 1841 * Where: 1842 * pkt_end == dst_reg, r2 == src_reg 1843 * r2=pkt(id=n,off=8,r=0) 1844 * r3=pkt(id=n,off=0,r=0) 1845 * 1846 * Find register r3 and mark its range as r3=pkt(id=n,off=0,r=8) 1847 * so that range of bytes [r3, r3 + 8) is safe to access. 1848 */ 1849 1850 for (i = 0; i < MAX_BPF_REG; i++) 1851 if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id) 1852 regs[i].range = dst_reg->off; 1853 1854 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 1855 if (state->stack_slot_type[i] != STACK_SPILL) 1856 continue; 1857 reg = &state->spilled_regs[i / BPF_REG_SIZE]; 1858 if (reg->type == PTR_TO_PACKET && reg->id == dst_reg->id) 1859 reg->range = dst_reg->off; 1860 } 1861 } 1862 1863 /* Adjusts the register min/max values in the case that the dst_reg is the 1864 * variable register that we are working on, and src_reg is a constant or we're 1865 * simply doing a BPF_K check. 1866 */ 1867 static void reg_set_min_max(struct bpf_reg_state *true_reg, 1868 struct bpf_reg_state *false_reg, u64 val, 1869 u8 opcode) 1870 { 1871 switch (opcode) { 1872 case BPF_JEQ: 1873 /* If this is false then we know nothing Jon Snow, but if it is 1874 * true then we know for sure. 1875 */ 1876 true_reg->max_value = true_reg->min_value = val; 1877 break; 1878 case BPF_JNE: 1879 /* If this is true we know nothing Jon Snow, but if it is false 1880 * we know the value for sure; 1881 */ 1882 false_reg->max_value = false_reg->min_value = val; 1883 break; 1884 case BPF_JGT: 1885 /* Unsigned comparison, the minimum value is 0. */ 1886 false_reg->min_value = 0; 1887 case BPF_JSGT: 1888 /* If this is false then we know the maximum val is val, 1889 * otherwise we know the min val is val+1. 1890 */ 1891 false_reg->max_value = val; 1892 true_reg->min_value = val + 1; 1893 break; 1894 case BPF_JGE: 1895 /* Unsigned comparison, the minimum value is 0. */ 1896 false_reg->min_value = 0; 1897 case BPF_JSGE: 1898 /* If this is false then we know the maximum value is val - 1, 1899 * otherwise we know the mimimum value is val. 1900 */ 1901 false_reg->max_value = val - 1; 1902 true_reg->min_value = val; 1903 break; 1904 default: 1905 break; 1906 } 1907 1908 check_reg_overflow(false_reg); 1909 check_reg_overflow(true_reg); 1910 } 1911 1912 /* Same as above, but for the case that dst_reg is a CONST_IMM reg and src_reg 1913 * is the variable reg. 1914 */ 1915 static void reg_set_min_max_inv(struct bpf_reg_state *true_reg, 1916 struct bpf_reg_state *false_reg, u64 val, 1917 u8 opcode) 1918 { 1919 switch (opcode) { 1920 case BPF_JEQ: 1921 /* If this is false then we know nothing Jon Snow, but if it is 1922 * true then we know for sure. 1923 */ 1924 true_reg->max_value = true_reg->min_value = val; 1925 break; 1926 case BPF_JNE: 1927 /* If this is true we know nothing Jon Snow, but if it is false 1928 * we know the value for sure; 1929 */ 1930 false_reg->max_value = false_reg->min_value = val; 1931 break; 1932 case BPF_JGT: 1933 /* Unsigned comparison, the minimum value is 0. */ 1934 true_reg->min_value = 0; 1935 case BPF_JSGT: 1936 /* 1937 * If this is false, then the val is <= the register, if it is 1938 * true the register <= to the val. 1939 */ 1940 false_reg->min_value = val; 1941 true_reg->max_value = val - 1; 1942 break; 1943 case BPF_JGE: 1944 /* Unsigned comparison, the minimum value is 0. */ 1945 true_reg->min_value = 0; 1946 case BPF_JSGE: 1947 /* If this is false then constant < register, if it is true then 1948 * the register < constant. 1949 */ 1950 false_reg->min_value = val + 1; 1951 true_reg->max_value = val; 1952 break; 1953 default: 1954 break; 1955 } 1956 1957 check_reg_overflow(false_reg); 1958 check_reg_overflow(true_reg); 1959 } 1960 1961 static void mark_map_reg(struct bpf_reg_state *regs, u32 regno, u32 id, 1962 enum bpf_reg_type type) 1963 { 1964 struct bpf_reg_state *reg = ®s[regno]; 1965 1966 if (reg->type == PTR_TO_MAP_VALUE_OR_NULL && reg->id == id) { 1967 reg->type = type; 1968 if (type == UNKNOWN_VALUE) 1969 mark_reg_unknown_value(regs, regno); 1970 } 1971 } 1972 1973 /* The logic is similar to find_good_pkt_pointers(), both could eventually 1974 * be folded together at some point. 1975 */ 1976 static void mark_map_regs(struct bpf_verifier_state *state, u32 regno, 1977 enum bpf_reg_type type) 1978 { 1979 struct bpf_reg_state *regs = state->regs; 1980 int i; 1981 1982 for (i = 0; i < MAX_BPF_REG; i++) 1983 mark_map_reg(regs, i, regs[regno].id, type); 1984 1985 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 1986 if (state->stack_slot_type[i] != STACK_SPILL) 1987 continue; 1988 mark_map_reg(state->spilled_regs, i / BPF_REG_SIZE, 1989 regs[regno].id, type); 1990 } 1991 } 1992 1993 static int check_cond_jmp_op(struct bpf_verifier_env *env, 1994 struct bpf_insn *insn, int *insn_idx) 1995 { 1996 struct bpf_verifier_state *other_branch, *this_branch = &env->cur_state; 1997 struct bpf_reg_state *regs = this_branch->regs, *dst_reg; 1998 u8 opcode = BPF_OP(insn->code); 1999 int err; 2000 2001 if (opcode > BPF_EXIT) { 2002 verbose("invalid BPF_JMP opcode %x\n", opcode); 2003 return -EINVAL; 2004 } 2005 2006 if (BPF_SRC(insn->code) == BPF_X) { 2007 if (insn->imm != 0) { 2008 verbose("BPF_JMP uses reserved fields\n"); 2009 return -EINVAL; 2010 } 2011 2012 /* check src1 operand */ 2013 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2014 if (err) 2015 return err; 2016 2017 if (is_pointer_value(env, insn->src_reg)) { 2018 verbose("R%d pointer comparison prohibited\n", 2019 insn->src_reg); 2020 return -EACCES; 2021 } 2022 } else { 2023 if (insn->src_reg != BPF_REG_0) { 2024 verbose("BPF_JMP uses reserved fields\n"); 2025 return -EINVAL; 2026 } 2027 } 2028 2029 /* check src2 operand */ 2030 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 2031 if (err) 2032 return err; 2033 2034 dst_reg = ®s[insn->dst_reg]; 2035 2036 /* detect if R == 0 where R was initialized to zero earlier */ 2037 if (BPF_SRC(insn->code) == BPF_K && 2038 (opcode == BPF_JEQ || opcode == BPF_JNE) && 2039 dst_reg->type == CONST_IMM && dst_reg->imm == insn->imm) { 2040 if (opcode == BPF_JEQ) { 2041 /* if (imm == imm) goto pc+off; 2042 * only follow the goto, ignore fall-through 2043 */ 2044 *insn_idx += insn->off; 2045 return 0; 2046 } else { 2047 /* if (imm != imm) goto pc+off; 2048 * only follow fall-through branch, since 2049 * that's where the program will go 2050 */ 2051 return 0; 2052 } 2053 } 2054 2055 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx); 2056 if (!other_branch) 2057 return -EFAULT; 2058 2059 /* detect if we are comparing against a constant value so we can adjust 2060 * our min/max values for our dst register. 2061 */ 2062 if (BPF_SRC(insn->code) == BPF_X) { 2063 if (regs[insn->src_reg].type == CONST_IMM) 2064 reg_set_min_max(&other_branch->regs[insn->dst_reg], 2065 dst_reg, regs[insn->src_reg].imm, 2066 opcode); 2067 else if (dst_reg->type == CONST_IMM) 2068 reg_set_min_max_inv(&other_branch->regs[insn->src_reg], 2069 ®s[insn->src_reg], dst_reg->imm, 2070 opcode); 2071 } else { 2072 reg_set_min_max(&other_branch->regs[insn->dst_reg], 2073 dst_reg, insn->imm, opcode); 2074 } 2075 2076 /* detect if R == 0 where R is returned from bpf_map_lookup_elem() */ 2077 if (BPF_SRC(insn->code) == BPF_K && 2078 insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) && 2079 dst_reg->type == PTR_TO_MAP_VALUE_OR_NULL) { 2080 /* Mark all identical map registers in each branch as either 2081 * safe or unknown depending R == 0 or R != 0 conditional. 2082 */ 2083 mark_map_regs(this_branch, insn->dst_reg, 2084 opcode == BPF_JEQ ? PTR_TO_MAP_VALUE : UNKNOWN_VALUE); 2085 mark_map_regs(other_branch, insn->dst_reg, 2086 opcode == BPF_JEQ ? UNKNOWN_VALUE : PTR_TO_MAP_VALUE); 2087 } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT && 2088 dst_reg->type == PTR_TO_PACKET && 2089 regs[insn->src_reg].type == PTR_TO_PACKET_END) { 2090 find_good_pkt_pointers(this_branch, dst_reg); 2091 } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGE && 2092 dst_reg->type == PTR_TO_PACKET_END && 2093 regs[insn->src_reg].type == PTR_TO_PACKET) { 2094 find_good_pkt_pointers(other_branch, ®s[insn->src_reg]); 2095 } else if (is_pointer_value(env, insn->dst_reg)) { 2096 verbose("R%d pointer comparison prohibited\n", insn->dst_reg); 2097 return -EACCES; 2098 } 2099 if (log_level) 2100 print_verifier_state(this_branch); 2101 return 0; 2102 } 2103 2104 /* return the map pointer stored inside BPF_LD_IMM64 instruction */ 2105 static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn) 2106 { 2107 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32; 2108 2109 return (struct bpf_map *) (unsigned long) imm64; 2110 } 2111 2112 /* verify BPF_LD_IMM64 instruction */ 2113 static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn) 2114 { 2115 struct bpf_reg_state *regs = env->cur_state.regs; 2116 int err; 2117 2118 if (BPF_SIZE(insn->code) != BPF_DW) { 2119 verbose("invalid BPF_LD_IMM insn\n"); 2120 return -EINVAL; 2121 } 2122 if (insn->off != 0) { 2123 verbose("BPF_LD_IMM64 uses reserved fields\n"); 2124 return -EINVAL; 2125 } 2126 2127 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 2128 if (err) 2129 return err; 2130 2131 if (insn->src_reg == 0) { 2132 /* generic move 64-bit immediate into a register, 2133 * only analyzer needs to collect the ld_imm value. 2134 */ 2135 u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm; 2136 2137 if (!env->analyzer_ops) 2138 return 0; 2139 2140 regs[insn->dst_reg].type = CONST_IMM; 2141 regs[insn->dst_reg].imm = imm; 2142 return 0; 2143 } 2144 2145 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */ 2146 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD); 2147 2148 regs[insn->dst_reg].type = CONST_PTR_TO_MAP; 2149 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn); 2150 return 0; 2151 } 2152 2153 static bool may_access_skb(enum bpf_prog_type type) 2154 { 2155 switch (type) { 2156 case BPF_PROG_TYPE_SOCKET_FILTER: 2157 case BPF_PROG_TYPE_SCHED_CLS: 2158 case BPF_PROG_TYPE_SCHED_ACT: 2159 return true; 2160 default: 2161 return false; 2162 } 2163 } 2164 2165 /* verify safety of LD_ABS|LD_IND instructions: 2166 * - they can only appear in the programs where ctx == skb 2167 * - since they are wrappers of function calls, they scratch R1-R5 registers, 2168 * preserve R6-R9, and store return value into R0 2169 * 2170 * Implicit input: 2171 * ctx == skb == R6 == CTX 2172 * 2173 * Explicit input: 2174 * SRC == any register 2175 * IMM == 32-bit immediate 2176 * 2177 * Output: 2178 * R0 - 8/16/32-bit skb data converted to cpu endianness 2179 */ 2180 static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn) 2181 { 2182 struct bpf_reg_state *regs = env->cur_state.regs; 2183 u8 mode = BPF_MODE(insn->code); 2184 struct bpf_reg_state *reg; 2185 int i, err; 2186 2187 if (!may_access_skb(env->prog->type)) { 2188 verbose("BPF_LD_[ABS|IND] instructions not allowed for this program type\n"); 2189 return -EINVAL; 2190 } 2191 2192 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 || 2193 BPF_SIZE(insn->code) == BPF_DW || 2194 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) { 2195 verbose("BPF_LD_[ABS|IND] uses reserved fields\n"); 2196 return -EINVAL; 2197 } 2198 2199 /* check whether implicit source operand (register R6) is readable */ 2200 err = check_reg_arg(regs, BPF_REG_6, SRC_OP); 2201 if (err) 2202 return err; 2203 2204 if (regs[BPF_REG_6].type != PTR_TO_CTX) { 2205 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n"); 2206 return -EINVAL; 2207 } 2208 2209 if (mode == BPF_IND) { 2210 /* check explicit source operand */ 2211 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2212 if (err) 2213 return err; 2214 } 2215 2216 /* reset caller saved regs to unreadable */ 2217 for (i = 0; i < CALLER_SAVED_REGS; i++) { 2218 reg = regs + caller_saved[i]; 2219 reg->type = NOT_INIT; 2220 reg->imm = 0; 2221 } 2222 2223 /* mark destination R0 register as readable, since it contains 2224 * the value fetched from the packet 2225 */ 2226 regs[BPF_REG_0].type = UNKNOWN_VALUE; 2227 return 0; 2228 } 2229 2230 /* non-recursive DFS pseudo code 2231 * 1 procedure DFS-iterative(G,v): 2232 * 2 label v as discovered 2233 * 3 let S be a stack 2234 * 4 S.push(v) 2235 * 5 while S is not empty 2236 * 6 t <- S.pop() 2237 * 7 if t is what we're looking for: 2238 * 8 return t 2239 * 9 for all edges e in G.adjacentEdges(t) do 2240 * 10 if edge e is already labelled 2241 * 11 continue with the next edge 2242 * 12 w <- G.adjacentVertex(t,e) 2243 * 13 if vertex w is not discovered and not explored 2244 * 14 label e as tree-edge 2245 * 15 label w as discovered 2246 * 16 S.push(w) 2247 * 17 continue at 5 2248 * 18 else if vertex w is discovered 2249 * 19 label e as back-edge 2250 * 20 else 2251 * 21 // vertex w is explored 2252 * 22 label e as forward- or cross-edge 2253 * 23 label t as explored 2254 * 24 S.pop() 2255 * 2256 * convention: 2257 * 0x10 - discovered 2258 * 0x11 - discovered and fall-through edge labelled 2259 * 0x12 - discovered and fall-through and branch edges labelled 2260 * 0x20 - explored 2261 */ 2262 2263 enum { 2264 DISCOVERED = 0x10, 2265 EXPLORED = 0x20, 2266 FALLTHROUGH = 1, 2267 BRANCH = 2, 2268 }; 2269 2270 #define STATE_LIST_MARK ((struct bpf_verifier_state_list *) -1L) 2271 2272 static int *insn_stack; /* stack of insns to process */ 2273 static int cur_stack; /* current stack index */ 2274 static int *insn_state; 2275 2276 /* t, w, e - match pseudo-code above: 2277 * t - index of current instruction 2278 * w - next instruction 2279 * e - edge 2280 */ 2281 static int push_insn(int t, int w, int e, struct bpf_verifier_env *env) 2282 { 2283 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH)) 2284 return 0; 2285 2286 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH)) 2287 return 0; 2288 2289 if (w < 0 || w >= env->prog->len) { 2290 verbose("jump out of range from insn %d to %d\n", t, w); 2291 return -EINVAL; 2292 } 2293 2294 if (e == BRANCH) 2295 /* mark branch target for state pruning */ 2296 env->explored_states[w] = STATE_LIST_MARK; 2297 2298 if (insn_state[w] == 0) { 2299 /* tree-edge */ 2300 insn_state[t] = DISCOVERED | e; 2301 insn_state[w] = DISCOVERED; 2302 if (cur_stack >= env->prog->len) 2303 return -E2BIG; 2304 insn_stack[cur_stack++] = w; 2305 return 1; 2306 } else if ((insn_state[w] & 0xF0) == DISCOVERED) { 2307 verbose("back-edge from insn %d to %d\n", t, w); 2308 return -EINVAL; 2309 } else if (insn_state[w] == EXPLORED) { 2310 /* forward- or cross-edge */ 2311 insn_state[t] = DISCOVERED | e; 2312 } else { 2313 verbose("insn state internal bug\n"); 2314 return -EFAULT; 2315 } 2316 return 0; 2317 } 2318 2319 /* non-recursive depth-first-search to detect loops in BPF program 2320 * loop == back-edge in directed graph 2321 */ 2322 static int check_cfg(struct bpf_verifier_env *env) 2323 { 2324 struct bpf_insn *insns = env->prog->insnsi; 2325 int insn_cnt = env->prog->len; 2326 int ret = 0; 2327 int i, t; 2328 2329 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 2330 if (!insn_state) 2331 return -ENOMEM; 2332 2333 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 2334 if (!insn_stack) { 2335 kfree(insn_state); 2336 return -ENOMEM; 2337 } 2338 2339 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */ 2340 insn_stack[0] = 0; /* 0 is the first instruction */ 2341 cur_stack = 1; 2342 2343 peek_stack: 2344 if (cur_stack == 0) 2345 goto check_state; 2346 t = insn_stack[cur_stack - 1]; 2347 2348 if (BPF_CLASS(insns[t].code) == BPF_JMP) { 2349 u8 opcode = BPF_OP(insns[t].code); 2350 2351 if (opcode == BPF_EXIT) { 2352 goto mark_explored; 2353 } else if (opcode == BPF_CALL) { 2354 ret = push_insn(t, t + 1, FALLTHROUGH, env); 2355 if (ret == 1) 2356 goto peek_stack; 2357 else if (ret < 0) 2358 goto err_free; 2359 if (t + 1 < insn_cnt) 2360 env->explored_states[t + 1] = STATE_LIST_MARK; 2361 } else if (opcode == BPF_JA) { 2362 if (BPF_SRC(insns[t].code) != BPF_K) { 2363 ret = -EINVAL; 2364 goto err_free; 2365 } 2366 /* unconditional jump with single edge */ 2367 ret = push_insn(t, t + insns[t].off + 1, 2368 FALLTHROUGH, env); 2369 if (ret == 1) 2370 goto peek_stack; 2371 else if (ret < 0) 2372 goto err_free; 2373 /* tell verifier to check for equivalent states 2374 * after every call and jump 2375 */ 2376 if (t + 1 < insn_cnt) 2377 env->explored_states[t + 1] = STATE_LIST_MARK; 2378 } else { 2379 /* conditional jump with two edges */ 2380 ret = push_insn(t, t + 1, FALLTHROUGH, env); 2381 if (ret == 1) 2382 goto peek_stack; 2383 else if (ret < 0) 2384 goto err_free; 2385 2386 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env); 2387 if (ret == 1) 2388 goto peek_stack; 2389 else if (ret < 0) 2390 goto err_free; 2391 } 2392 } else { 2393 /* all other non-branch instructions with single 2394 * fall-through edge 2395 */ 2396 ret = push_insn(t, t + 1, FALLTHROUGH, env); 2397 if (ret == 1) 2398 goto peek_stack; 2399 else if (ret < 0) 2400 goto err_free; 2401 } 2402 2403 mark_explored: 2404 insn_state[t] = EXPLORED; 2405 if (cur_stack-- <= 0) { 2406 verbose("pop stack internal bug\n"); 2407 ret = -EFAULT; 2408 goto err_free; 2409 } 2410 goto peek_stack; 2411 2412 check_state: 2413 for (i = 0; i < insn_cnt; i++) { 2414 if (insn_state[i] != EXPLORED) { 2415 verbose("unreachable insn %d\n", i); 2416 ret = -EINVAL; 2417 goto err_free; 2418 } 2419 } 2420 ret = 0; /* cfg looks good */ 2421 2422 err_free: 2423 kfree(insn_state); 2424 kfree(insn_stack); 2425 return ret; 2426 } 2427 2428 /* the following conditions reduce the number of explored insns 2429 * from ~140k to ~80k for ultra large programs that use a lot of ptr_to_packet 2430 */ 2431 static bool compare_ptrs_to_packet(struct bpf_reg_state *old, 2432 struct bpf_reg_state *cur) 2433 { 2434 if (old->id != cur->id) 2435 return false; 2436 2437 /* old ptr_to_packet is more conservative, since it allows smaller 2438 * range. Ex: 2439 * old(off=0,r=10) is equal to cur(off=0,r=20), because 2440 * old(off=0,r=10) means that with range=10 the verifier proceeded 2441 * further and found no issues with the program. Now we're in the same 2442 * spot with cur(off=0,r=20), so we're safe too, since anything further 2443 * will only be looking at most 10 bytes after this pointer. 2444 */ 2445 if (old->off == cur->off && old->range < cur->range) 2446 return true; 2447 2448 /* old(off=20,r=10) is equal to cur(off=22,re=22 or 5 or 0) 2449 * since both cannot be used for packet access and safe(old) 2450 * pointer has smaller off that could be used for further 2451 * 'if (ptr > data_end)' check 2452 * Ex: 2453 * old(off=20,r=10) and cur(off=22,r=22) and cur(off=22,r=0) mean 2454 * that we cannot access the packet. 2455 * The safe range is: 2456 * [ptr, ptr + range - off) 2457 * so whenever off >=range, it means no safe bytes from this pointer. 2458 * When comparing old->off <= cur->off, it means that older code 2459 * went with smaller offset and that offset was later 2460 * used to figure out the safe range after 'if (ptr > data_end)' check 2461 * Say, 'old' state was explored like: 2462 * ... R3(off=0, r=0) 2463 * R4 = R3 + 20 2464 * ... now R4(off=20,r=0) <-- here 2465 * if (R4 > data_end) 2466 * ... R4(off=20,r=20), R3(off=0,r=20) and R3 can be used to access. 2467 * ... the code further went all the way to bpf_exit. 2468 * Now the 'cur' state at the mark 'here' has R4(off=30,r=0). 2469 * old_R4(off=20,r=0) equal to cur_R4(off=30,r=0), since if the verifier 2470 * goes further, such cur_R4 will give larger safe packet range after 2471 * 'if (R4 > data_end)' and all further insn were already good with r=20, 2472 * so they will be good with r=30 and we can prune the search. 2473 */ 2474 if (old->off <= cur->off && 2475 old->off >= old->range && cur->off >= cur->range) 2476 return true; 2477 2478 return false; 2479 } 2480 2481 /* compare two verifier states 2482 * 2483 * all states stored in state_list are known to be valid, since 2484 * verifier reached 'bpf_exit' instruction through them 2485 * 2486 * this function is called when verifier exploring different branches of 2487 * execution popped from the state stack. If it sees an old state that has 2488 * more strict register state and more strict stack state then this execution 2489 * branch doesn't need to be explored further, since verifier already 2490 * concluded that more strict state leads to valid finish. 2491 * 2492 * Therefore two states are equivalent if register state is more conservative 2493 * and explored stack state is more conservative than the current one. 2494 * Example: 2495 * explored current 2496 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC) 2497 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC) 2498 * 2499 * In other words if current stack state (one being explored) has more 2500 * valid slots than old one that already passed validation, it means 2501 * the verifier can stop exploring and conclude that current state is valid too 2502 * 2503 * Similarly with registers. If explored state has register type as invalid 2504 * whereas register type in current state is meaningful, it means that 2505 * the current state will reach 'bpf_exit' instruction safely 2506 */ 2507 static bool states_equal(struct bpf_verifier_env *env, 2508 struct bpf_verifier_state *old, 2509 struct bpf_verifier_state *cur) 2510 { 2511 bool varlen_map_access = env->varlen_map_value_access; 2512 struct bpf_reg_state *rold, *rcur; 2513 int i; 2514 2515 for (i = 0; i < MAX_BPF_REG; i++) { 2516 rold = &old->regs[i]; 2517 rcur = &cur->regs[i]; 2518 2519 if (memcmp(rold, rcur, sizeof(*rold)) == 0) 2520 continue; 2521 2522 /* If the ranges were not the same, but everything else was and 2523 * we didn't do a variable access into a map then we are a-ok. 2524 */ 2525 if (!varlen_map_access && 2526 rold->type == rcur->type && rold->imm == rcur->imm) 2527 continue; 2528 2529 /* If we didn't map access then again we don't care about the 2530 * mismatched range values and it's ok if our old type was 2531 * UNKNOWN and we didn't go to a NOT_INIT'ed reg. 2532 */ 2533 if (rold->type == NOT_INIT || 2534 (!varlen_map_access && rold->type == UNKNOWN_VALUE && 2535 rcur->type != NOT_INIT)) 2536 continue; 2537 2538 if (rold->type == PTR_TO_PACKET && rcur->type == PTR_TO_PACKET && 2539 compare_ptrs_to_packet(rold, rcur)) 2540 continue; 2541 2542 return false; 2543 } 2544 2545 for (i = 0; i < MAX_BPF_STACK; i++) { 2546 if (old->stack_slot_type[i] == STACK_INVALID) 2547 continue; 2548 if (old->stack_slot_type[i] != cur->stack_slot_type[i]) 2549 /* Ex: old explored (safe) state has STACK_SPILL in 2550 * this stack slot, but current has has STACK_MISC -> 2551 * this verifier states are not equivalent, 2552 * return false to continue verification of this path 2553 */ 2554 return false; 2555 if (i % BPF_REG_SIZE) 2556 continue; 2557 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE], 2558 &cur->spilled_regs[i / BPF_REG_SIZE], 2559 sizeof(old->spilled_regs[0]))) 2560 /* when explored and current stack slot types are 2561 * the same, check that stored pointers types 2562 * are the same as well. 2563 * Ex: explored safe path could have stored 2564 * (bpf_reg_state) {.type = PTR_TO_STACK, .imm = -8} 2565 * but current path has stored: 2566 * (bpf_reg_state) {.type = PTR_TO_STACK, .imm = -16} 2567 * such verifier states are not equivalent. 2568 * return false to continue verification of this path 2569 */ 2570 return false; 2571 else 2572 continue; 2573 } 2574 return true; 2575 } 2576 2577 static int is_state_visited(struct bpf_verifier_env *env, int insn_idx) 2578 { 2579 struct bpf_verifier_state_list *new_sl; 2580 struct bpf_verifier_state_list *sl; 2581 2582 sl = env->explored_states[insn_idx]; 2583 if (!sl) 2584 /* this 'insn_idx' instruction wasn't marked, so we will not 2585 * be doing state search here 2586 */ 2587 return 0; 2588 2589 while (sl != STATE_LIST_MARK) { 2590 if (states_equal(env, &sl->state, &env->cur_state)) 2591 /* reached equivalent register/stack state, 2592 * prune the search 2593 */ 2594 return 1; 2595 sl = sl->next; 2596 } 2597 2598 /* there were no equivalent states, remember current one. 2599 * technically the current state is not proven to be safe yet, 2600 * but it will either reach bpf_exit (which means it's safe) or 2601 * it will be rejected. Since there are no loops, we won't be 2602 * seeing this 'insn_idx' instruction again on the way to bpf_exit 2603 */ 2604 new_sl = kmalloc(sizeof(struct bpf_verifier_state_list), GFP_USER); 2605 if (!new_sl) 2606 return -ENOMEM; 2607 2608 /* add new state to the head of linked list */ 2609 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state)); 2610 new_sl->next = env->explored_states[insn_idx]; 2611 env->explored_states[insn_idx] = new_sl; 2612 return 0; 2613 } 2614 2615 static int ext_analyzer_insn_hook(struct bpf_verifier_env *env, 2616 int insn_idx, int prev_insn_idx) 2617 { 2618 if (!env->analyzer_ops || !env->analyzer_ops->insn_hook) 2619 return 0; 2620 2621 return env->analyzer_ops->insn_hook(env, insn_idx, prev_insn_idx); 2622 } 2623 2624 static int do_check(struct bpf_verifier_env *env) 2625 { 2626 struct bpf_verifier_state *state = &env->cur_state; 2627 struct bpf_insn *insns = env->prog->insnsi; 2628 struct bpf_reg_state *regs = state->regs; 2629 int insn_cnt = env->prog->len; 2630 int insn_idx, prev_insn_idx = 0; 2631 int insn_processed = 0; 2632 bool do_print_state = false; 2633 2634 init_reg_state(regs); 2635 insn_idx = 0; 2636 env->varlen_map_value_access = false; 2637 for (;;) { 2638 struct bpf_insn *insn; 2639 u8 class; 2640 int err; 2641 2642 if (insn_idx >= insn_cnt) { 2643 verbose("invalid insn idx %d insn_cnt %d\n", 2644 insn_idx, insn_cnt); 2645 return -EFAULT; 2646 } 2647 2648 insn = &insns[insn_idx]; 2649 class = BPF_CLASS(insn->code); 2650 2651 if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) { 2652 verbose("BPF program is too large. Proccessed %d insn\n", 2653 insn_processed); 2654 return -E2BIG; 2655 } 2656 2657 err = is_state_visited(env, insn_idx); 2658 if (err < 0) 2659 return err; 2660 if (err == 1) { 2661 /* found equivalent state, can prune the search */ 2662 if (log_level) { 2663 if (do_print_state) 2664 verbose("\nfrom %d to %d: safe\n", 2665 prev_insn_idx, insn_idx); 2666 else 2667 verbose("%d: safe\n", insn_idx); 2668 } 2669 goto process_bpf_exit; 2670 } 2671 2672 if (log_level && do_print_state) { 2673 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx); 2674 print_verifier_state(&env->cur_state); 2675 do_print_state = false; 2676 } 2677 2678 if (log_level) { 2679 verbose("%d: ", insn_idx); 2680 print_bpf_insn(insn); 2681 } 2682 2683 err = ext_analyzer_insn_hook(env, insn_idx, prev_insn_idx); 2684 if (err) 2685 return err; 2686 2687 if (class == BPF_ALU || class == BPF_ALU64) { 2688 err = check_alu_op(env, insn); 2689 if (err) 2690 return err; 2691 2692 } else if (class == BPF_LDX) { 2693 enum bpf_reg_type *prev_src_type, src_reg_type; 2694 2695 /* check for reserved fields is already done */ 2696 2697 /* check src operand */ 2698 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2699 if (err) 2700 return err; 2701 2702 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); 2703 if (err) 2704 return err; 2705 2706 src_reg_type = regs[insn->src_reg].type; 2707 2708 /* check that memory (src_reg + off) is readable, 2709 * the state of dst_reg will be updated by this func 2710 */ 2711 err = check_mem_access(env, insn->src_reg, insn->off, 2712 BPF_SIZE(insn->code), BPF_READ, 2713 insn->dst_reg); 2714 if (err) 2715 return err; 2716 2717 reset_reg_range_values(regs, insn->dst_reg); 2718 if (BPF_SIZE(insn->code) != BPF_W && 2719 BPF_SIZE(insn->code) != BPF_DW) { 2720 insn_idx++; 2721 continue; 2722 } 2723 2724 prev_src_type = &env->insn_aux_data[insn_idx].ptr_type; 2725 2726 if (*prev_src_type == NOT_INIT) { 2727 /* saw a valid insn 2728 * dst_reg = *(u32 *)(src_reg + off) 2729 * save type to validate intersecting paths 2730 */ 2731 *prev_src_type = src_reg_type; 2732 2733 } else if (src_reg_type != *prev_src_type && 2734 (src_reg_type == PTR_TO_CTX || 2735 *prev_src_type == PTR_TO_CTX)) { 2736 /* ABuser program is trying to use the same insn 2737 * dst_reg = *(u32*) (src_reg + off) 2738 * with different pointer types: 2739 * src_reg == ctx in one branch and 2740 * src_reg == stack|map in some other branch. 2741 * Reject it. 2742 */ 2743 verbose("same insn cannot be used with different pointers\n"); 2744 return -EINVAL; 2745 } 2746 2747 } else if (class == BPF_STX) { 2748 enum bpf_reg_type *prev_dst_type, dst_reg_type; 2749 2750 if (BPF_MODE(insn->code) == BPF_XADD) { 2751 err = check_xadd(env, insn); 2752 if (err) 2753 return err; 2754 insn_idx++; 2755 continue; 2756 } 2757 2758 /* check src1 operand */ 2759 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2760 if (err) 2761 return err; 2762 /* check src2 operand */ 2763 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 2764 if (err) 2765 return err; 2766 2767 dst_reg_type = regs[insn->dst_reg].type; 2768 2769 /* check that memory (dst_reg + off) is writeable */ 2770 err = check_mem_access(env, insn->dst_reg, insn->off, 2771 BPF_SIZE(insn->code), BPF_WRITE, 2772 insn->src_reg); 2773 if (err) 2774 return err; 2775 2776 prev_dst_type = &env->insn_aux_data[insn_idx].ptr_type; 2777 2778 if (*prev_dst_type == NOT_INIT) { 2779 *prev_dst_type = dst_reg_type; 2780 } else if (dst_reg_type != *prev_dst_type && 2781 (dst_reg_type == PTR_TO_CTX || 2782 *prev_dst_type == PTR_TO_CTX)) { 2783 verbose("same insn cannot be used with different pointers\n"); 2784 return -EINVAL; 2785 } 2786 2787 } else if (class == BPF_ST) { 2788 if (BPF_MODE(insn->code) != BPF_MEM || 2789 insn->src_reg != BPF_REG_0) { 2790 verbose("BPF_ST uses reserved fields\n"); 2791 return -EINVAL; 2792 } 2793 /* check src operand */ 2794 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 2795 if (err) 2796 return err; 2797 2798 /* check that memory (dst_reg + off) is writeable */ 2799 err = check_mem_access(env, insn->dst_reg, insn->off, 2800 BPF_SIZE(insn->code), BPF_WRITE, 2801 -1); 2802 if (err) 2803 return err; 2804 2805 } else if (class == BPF_JMP) { 2806 u8 opcode = BPF_OP(insn->code); 2807 2808 if (opcode == BPF_CALL) { 2809 if (BPF_SRC(insn->code) != BPF_K || 2810 insn->off != 0 || 2811 insn->src_reg != BPF_REG_0 || 2812 insn->dst_reg != BPF_REG_0) { 2813 verbose("BPF_CALL uses reserved fields\n"); 2814 return -EINVAL; 2815 } 2816 2817 err = check_call(env, insn->imm); 2818 if (err) 2819 return err; 2820 2821 } else if (opcode == BPF_JA) { 2822 if (BPF_SRC(insn->code) != BPF_K || 2823 insn->imm != 0 || 2824 insn->src_reg != BPF_REG_0 || 2825 insn->dst_reg != BPF_REG_0) { 2826 verbose("BPF_JA uses reserved fields\n"); 2827 return -EINVAL; 2828 } 2829 2830 insn_idx += insn->off + 1; 2831 continue; 2832 2833 } else if (opcode == BPF_EXIT) { 2834 if (BPF_SRC(insn->code) != BPF_K || 2835 insn->imm != 0 || 2836 insn->src_reg != BPF_REG_0 || 2837 insn->dst_reg != BPF_REG_0) { 2838 verbose("BPF_EXIT uses reserved fields\n"); 2839 return -EINVAL; 2840 } 2841 2842 /* eBPF calling convetion is such that R0 is used 2843 * to return the value from eBPF program. 2844 * Make sure that it's readable at this time 2845 * of bpf_exit, which means that program wrote 2846 * something into it earlier 2847 */ 2848 err = check_reg_arg(regs, BPF_REG_0, SRC_OP); 2849 if (err) 2850 return err; 2851 2852 if (is_pointer_value(env, BPF_REG_0)) { 2853 verbose("R0 leaks addr as return value\n"); 2854 return -EACCES; 2855 } 2856 2857 process_bpf_exit: 2858 insn_idx = pop_stack(env, &prev_insn_idx); 2859 if (insn_idx < 0) { 2860 break; 2861 } else { 2862 do_print_state = true; 2863 continue; 2864 } 2865 } else { 2866 err = check_cond_jmp_op(env, insn, &insn_idx); 2867 if (err) 2868 return err; 2869 } 2870 } else if (class == BPF_LD) { 2871 u8 mode = BPF_MODE(insn->code); 2872 2873 if (mode == BPF_ABS || mode == BPF_IND) { 2874 err = check_ld_abs(env, insn); 2875 if (err) 2876 return err; 2877 2878 } else if (mode == BPF_IMM) { 2879 err = check_ld_imm(env, insn); 2880 if (err) 2881 return err; 2882 2883 insn_idx++; 2884 } else { 2885 verbose("invalid BPF_LD mode\n"); 2886 return -EINVAL; 2887 } 2888 reset_reg_range_values(regs, insn->dst_reg); 2889 } else { 2890 verbose("unknown insn class %d\n", class); 2891 return -EINVAL; 2892 } 2893 2894 insn_idx++; 2895 } 2896 2897 verbose("processed %d insns\n", insn_processed); 2898 return 0; 2899 } 2900 2901 static int check_map_prog_compatibility(struct bpf_map *map, 2902 struct bpf_prog *prog) 2903 2904 { 2905 if (prog->type == BPF_PROG_TYPE_PERF_EVENT && 2906 (map->map_type == BPF_MAP_TYPE_HASH || 2907 map->map_type == BPF_MAP_TYPE_PERCPU_HASH) && 2908 (map->map_flags & BPF_F_NO_PREALLOC)) { 2909 verbose("perf_event programs can only use preallocated hash map\n"); 2910 return -EINVAL; 2911 } 2912 return 0; 2913 } 2914 2915 /* look for pseudo eBPF instructions that access map FDs and 2916 * replace them with actual map pointers 2917 */ 2918 static int replace_map_fd_with_map_ptr(struct bpf_verifier_env *env) 2919 { 2920 struct bpf_insn *insn = env->prog->insnsi; 2921 int insn_cnt = env->prog->len; 2922 int i, j, err; 2923 2924 for (i = 0; i < insn_cnt; i++, insn++) { 2925 if (BPF_CLASS(insn->code) == BPF_LDX && 2926 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) { 2927 verbose("BPF_LDX uses reserved fields\n"); 2928 return -EINVAL; 2929 } 2930 2931 if (BPF_CLASS(insn->code) == BPF_STX && 2932 ((BPF_MODE(insn->code) != BPF_MEM && 2933 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) { 2934 verbose("BPF_STX uses reserved fields\n"); 2935 return -EINVAL; 2936 } 2937 2938 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) { 2939 struct bpf_map *map; 2940 struct fd f; 2941 2942 if (i == insn_cnt - 1 || insn[1].code != 0 || 2943 insn[1].dst_reg != 0 || insn[1].src_reg != 0 || 2944 insn[1].off != 0) { 2945 verbose("invalid bpf_ld_imm64 insn\n"); 2946 return -EINVAL; 2947 } 2948 2949 if (insn->src_reg == 0) 2950 /* valid generic load 64-bit imm */ 2951 goto next_insn; 2952 2953 if (insn->src_reg != BPF_PSEUDO_MAP_FD) { 2954 verbose("unrecognized bpf_ld_imm64 insn\n"); 2955 return -EINVAL; 2956 } 2957 2958 f = fdget(insn->imm); 2959 map = __bpf_map_get(f); 2960 if (IS_ERR(map)) { 2961 verbose("fd %d is not pointing to valid bpf_map\n", 2962 insn->imm); 2963 return PTR_ERR(map); 2964 } 2965 2966 err = check_map_prog_compatibility(map, env->prog); 2967 if (err) { 2968 fdput(f); 2969 return err; 2970 } 2971 2972 /* store map pointer inside BPF_LD_IMM64 instruction */ 2973 insn[0].imm = (u32) (unsigned long) map; 2974 insn[1].imm = ((u64) (unsigned long) map) >> 32; 2975 2976 /* check whether we recorded this map already */ 2977 for (j = 0; j < env->used_map_cnt; j++) 2978 if (env->used_maps[j] == map) { 2979 fdput(f); 2980 goto next_insn; 2981 } 2982 2983 if (env->used_map_cnt >= MAX_USED_MAPS) { 2984 fdput(f); 2985 return -E2BIG; 2986 } 2987 2988 /* hold the map. If the program is rejected by verifier, 2989 * the map will be released by release_maps() or it 2990 * will be used by the valid program until it's unloaded 2991 * and all maps are released in free_bpf_prog_info() 2992 */ 2993 map = bpf_map_inc(map, false); 2994 if (IS_ERR(map)) { 2995 fdput(f); 2996 return PTR_ERR(map); 2997 } 2998 env->used_maps[env->used_map_cnt++] = map; 2999 3000 fdput(f); 3001 next_insn: 3002 insn++; 3003 i++; 3004 } 3005 } 3006 3007 /* now all pseudo BPF_LD_IMM64 instructions load valid 3008 * 'struct bpf_map *' into a register instead of user map_fd. 3009 * These pointers will be used later by verifier to validate map access. 3010 */ 3011 return 0; 3012 } 3013 3014 /* drop refcnt of maps used by the rejected program */ 3015 static void release_maps(struct bpf_verifier_env *env) 3016 { 3017 int i; 3018 3019 for (i = 0; i < env->used_map_cnt; i++) 3020 bpf_map_put(env->used_maps[i]); 3021 } 3022 3023 /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */ 3024 static void convert_pseudo_ld_imm64(struct bpf_verifier_env *env) 3025 { 3026 struct bpf_insn *insn = env->prog->insnsi; 3027 int insn_cnt = env->prog->len; 3028 int i; 3029 3030 for (i = 0; i < insn_cnt; i++, insn++) 3031 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW)) 3032 insn->src_reg = 0; 3033 } 3034 3035 /* convert load instructions that access fields of 'struct __sk_buff' 3036 * into sequence of instructions that access fields of 'struct sk_buff' 3037 */ 3038 static int convert_ctx_accesses(struct bpf_verifier_env *env) 3039 { 3040 const struct bpf_verifier_ops *ops = env->prog->aux->ops; 3041 const int insn_cnt = env->prog->len; 3042 struct bpf_insn insn_buf[16], *insn; 3043 struct bpf_prog *new_prog; 3044 enum bpf_access_type type; 3045 int i, cnt, delta = 0; 3046 3047 if (ops->gen_prologue) { 3048 cnt = ops->gen_prologue(insn_buf, env->seen_direct_write, 3049 env->prog); 3050 if (cnt >= ARRAY_SIZE(insn_buf)) { 3051 verbose("bpf verifier is misconfigured\n"); 3052 return -EINVAL; 3053 } else if (cnt) { 3054 new_prog = bpf_patch_insn_single(env->prog, 0, 3055 insn_buf, cnt); 3056 if (!new_prog) 3057 return -ENOMEM; 3058 env->prog = new_prog; 3059 delta += cnt - 1; 3060 } 3061 } 3062 3063 if (!ops->convert_ctx_access) 3064 return 0; 3065 3066 insn = env->prog->insnsi + delta; 3067 3068 for (i = 0; i < insn_cnt; i++, insn++) { 3069 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W) || 3070 insn->code == (BPF_LDX | BPF_MEM | BPF_DW)) 3071 type = BPF_READ; 3072 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W) || 3073 insn->code == (BPF_STX | BPF_MEM | BPF_DW)) 3074 type = BPF_WRITE; 3075 else 3076 continue; 3077 3078 if (env->insn_aux_data[i].ptr_type != PTR_TO_CTX) 3079 continue; 3080 3081 cnt = ops->convert_ctx_access(type, insn->dst_reg, insn->src_reg, 3082 insn->off, insn_buf, env->prog); 3083 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) { 3084 verbose("bpf verifier is misconfigured\n"); 3085 return -EINVAL; 3086 } 3087 3088 new_prog = bpf_patch_insn_single(env->prog, i + delta, insn_buf, 3089 cnt); 3090 if (!new_prog) 3091 return -ENOMEM; 3092 3093 delta += cnt - 1; 3094 3095 /* keep walking new program and skip insns we just inserted */ 3096 env->prog = new_prog; 3097 insn = new_prog->insnsi + i + delta; 3098 } 3099 3100 return 0; 3101 } 3102 3103 static void free_states(struct bpf_verifier_env *env) 3104 { 3105 struct bpf_verifier_state_list *sl, *sln; 3106 int i; 3107 3108 if (!env->explored_states) 3109 return; 3110 3111 for (i = 0; i < env->prog->len; i++) { 3112 sl = env->explored_states[i]; 3113 3114 if (sl) 3115 while (sl != STATE_LIST_MARK) { 3116 sln = sl->next; 3117 kfree(sl); 3118 sl = sln; 3119 } 3120 } 3121 3122 kfree(env->explored_states); 3123 } 3124 3125 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) 3126 { 3127 char __user *log_ubuf = NULL; 3128 struct bpf_verifier_env *env; 3129 int ret = -EINVAL; 3130 3131 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS) 3132 return -E2BIG; 3133 3134 /* 'struct bpf_verifier_env' can be global, but since it's not small, 3135 * allocate/free it every time bpf_check() is called 3136 */ 3137 env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL); 3138 if (!env) 3139 return -ENOMEM; 3140 3141 env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) * 3142 (*prog)->len); 3143 ret = -ENOMEM; 3144 if (!env->insn_aux_data) 3145 goto err_free_env; 3146 env->prog = *prog; 3147 3148 /* grab the mutex to protect few globals used by verifier */ 3149 mutex_lock(&bpf_verifier_lock); 3150 3151 if (attr->log_level || attr->log_buf || attr->log_size) { 3152 /* user requested verbose verifier output 3153 * and supplied buffer to store the verification trace 3154 */ 3155 log_level = attr->log_level; 3156 log_ubuf = (char __user *) (unsigned long) attr->log_buf; 3157 log_size = attr->log_size; 3158 log_len = 0; 3159 3160 ret = -EINVAL; 3161 /* log_* values have to be sane */ 3162 if (log_size < 128 || log_size > UINT_MAX >> 8 || 3163 log_level == 0 || log_ubuf == NULL) 3164 goto err_unlock; 3165 3166 ret = -ENOMEM; 3167 log_buf = vmalloc(log_size); 3168 if (!log_buf) 3169 goto err_unlock; 3170 } else { 3171 log_level = 0; 3172 } 3173 3174 ret = replace_map_fd_with_map_ptr(env); 3175 if (ret < 0) 3176 goto skip_full_check; 3177 3178 env->explored_states = kcalloc(env->prog->len, 3179 sizeof(struct bpf_verifier_state_list *), 3180 GFP_USER); 3181 ret = -ENOMEM; 3182 if (!env->explored_states) 3183 goto skip_full_check; 3184 3185 ret = check_cfg(env); 3186 if (ret < 0) 3187 goto skip_full_check; 3188 3189 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); 3190 3191 ret = do_check(env); 3192 3193 skip_full_check: 3194 while (pop_stack(env, NULL) >= 0); 3195 free_states(env); 3196 3197 if (ret == 0) 3198 /* program is valid, convert *(u32*)(ctx + off) accesses */ 3199 ret = convert_ctx_accesses(env); 3200 3201 if (log_level && log_len >= log_size - 1) { 3202 BUG_ON(log_len >= log_size); 3203 /* verifier log exceeded user supplied buffer */ 3204 ret = -ENOSPC; 3205 /* fall through to return what was recorded */ 3206 } 3207 3208 /* copy verifier log back to user space including trailing zero */ 3209 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) { 3210 ret = -EFAULT; 3211 goto free_log_buf; 3212 } 3213 3214 if (ret == 0 && env->used_map_cnt) { 3215 /* if program passed verifier, update used_maps in bpf_prog_info */ 3216 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt, 3217 sizeof(env->used_maps[0]), 3218 GFP_KERNEL); 3219 3220 if (!env->prog->aux->used_maps) { 3221 ret = -ENOMEM; 3222 goto free_log_buf; 3223 } 3224 3225 memcpy(env->prog->aux->used_maps, env->used_maps, 3226 sizeof(env->used_maps[0]) * env->used_map_cnt); 3227 env->prog->aux->used_map_cnt = env->used_map_cnt; 3228 3229 /* program is valid. Convert pseudo bpf_ld_imm64 into generic 3230 * bpf_ld_imm64 instructions 3231 */ 3232 convert_pseudo_ld_imm64(env); 3233 } 3234 3235 free_log_buf: 3236 if (log_level) 3237 vfree(log_buf); 3238 if (!env->prog->aux->used_maps) 3239 /* if we didn't copy map pointers into bpf_prog_info, release 3240 * them now. Otherwise free_bpf_prog_info() will release them. 3241 */ 3242 release_maps(env); 3243 *prog = env->prog; 3244 err_unlock: 3245 mutex_unlock(&bpf_verifier_lock); 3246 vfree(env->insn_aux_data); 3247 err_free_env: 3248 kfree(env); 3249 return ret; 3250 } 3251 3252 int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops, 3253 void *priv) 3254 { 3255 struct bpf_verifier_env *env; 3256 int ret; 3257 3258 env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL); 3259 if (!env) 3260 return -ENOMEM; 3261 3262 env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) * 3263 prog->len); 3264 ret = -ENOMEM; 3265 if (!env->insn_aux_data) 3266 goto err_free_env; 3267 env->prog = prog; 3268 env->analyzer_ops = ops; 3269 env->analyzer_priv = priv; 3270 3271 /* grab the mutex to protect few globals used by verifier */ 3272 mutex_lock(&bpf_verifier_lock); 3273 3274 log_level = 0; 3275 3276 env->explored_states = kcalloc(env->prog->len, 3277 sizeof(struct bpf_verifier_state_list *), 3278 GFP_KERNEL); 3279 ret = -ENOMEM; 3280 if (!env->explored_states) 3281 goto skip_full_check; 3282 3283 ret = check_cfg(env); 3284 if (ret < 0) 3285 goto skip_full_check; 3286 3287 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); 3288 3289 ret = do_check(env); 3290 3291 skip_full_check: 3292 while (pop_stack(env, NULL) >= 0); 3293 free_states(env); 3294 3295 mutex_unlock(&bpf_verifier_lock); 3296 vfree(env->insn_aux_data); 3297 err_free_env: 3298 kfree(env); 3299 return ret; 3300 } 3301 EXPORT_SYMBOL_GPL(bpf_analyzer); 3302