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/filter.h> 18 #include <net/netlink.h> 19 #include <linux/file.h> 20 #include <linux/vmalloc.h> 21 22 /* bpf_check() is a static code analyzer that walks eBPF program 23 * instruction by instruction and updates register/stack state. 24 * All paths of conditional branches are analyzed until 'bpf_exit' insn. 25 * 26 * The first pass is depth-first-search to check that the program is a DAG. 27 * It rejects the following programs: 28 * - larger than BPF_MAXINSNS insns 29 * - if loop is present (detected via back-edge) 30 * - unreachable insns exist (shouldn't be a forest. program = one function) 31 * - out of bounds or malformed jumps 32 * The second pass is all possible path descent from the 1st insn. 33 * Since it's analyzing all pathes through the program, the length of the 34 * analysis is limited to 32k insn, which may be hit even if total number of 35 * insn is less then 4K, but there are too many branches that change stack/regs. 36 * Number of 'branches to be analyzed' is limited to 1k 37 * 38 * On entry to each instruction, each register has a type, and the instruction 39 * changes the types of the registers depending on instruction semantics. 40 * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is 41 * copied to R1. 42 * 43 * All registers are 64-bit. 44 * R0 - return register 45 * R1-R5 argument passing registers 46 * R6-R9 callee saved registers 47 * R10 - frame pointer read-only 48 * 49 * At the start of BPF program the register R1 contains a pointer to bpf_context 50 * and has type PTR_TO_CTX. 51 * 52 * Verifier tracks arithmetic operations on pointers in case: 53 * BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), 54 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20), 55 * 1st insn copies R10 (which has FRAME_PTR) type into R1 56 * and 2nd arithmetic instruction is pattern matched to recognize 57 * that it wants to construct a pointer to some element within stack. 58 * So after 2nd insn, the register R1 has type PTR_TO_STACK 59 * (and -20 constant is saved for further stack bounds checking). 60 * Meaning that this reg is a pointer to stack plus known immediate constant. 61 * 62 * Most of the time the registers have UNKNOWN_VALUE type, which 63 * means the register has some value, but it's not a valid pointer. 64 * (like pointer plus pointer becomes UNKNOWN_VALUE type) 65 * 66 * When verifier sees load or store instructions the type of base register 67 * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, FRAME_PTR. These are three pointer 68 * types recognized by check_mem_access() function. 69 * 70 * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value' 71 * and the range of [ptr, ptr + map's value_size) is accessible. 72 * 73 * registers used to pass values to function calls are checked against 74 * function argument constraints. 75 * 76 * ARG_PTR_TO_MAP_KEY is one of such argument constraints. 77 * It means that the register type passed to this function must be 78 * PTR_TO_STACK and it will be used inside the function as 79 * 'pointer to map element key' 80 * 81 * For example the argument constraints for bpf_map_lookup_elem(): 82 * .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, 83 * .arg1_type = ARG_CONST_MAP_PTR, 84 * .arg2_type = ARG_PTR_TO_MAP_KEY, 85 * 86 * ret_type says that this function returns 'pointer to map elem value or null' 87 * function expects 1st argument to be a const pointer to 'struct bpf_map' and 88 * 2nd argument should be a pointer to stack, which will be used inside 89 * the helper function as a pointer to map element key. 90 * 91 * On the kernel side the helper function looks like: 92 * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) 93 * { 94 * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1; 95 * void *key = (void *) (unsigned long) r2; 96 * void *value; 97 * 98 * here kernel can access 'key' and 'map' pointers safely, knowing that 99 * [key, key + map->key_size) bytes are valid and were initialized on 100 * the stack of eBPF program. 101 * } 102 * 103 * Corresponding eBPF program may look like: 104 * BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR 105 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK 106 * BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP 107 * BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), 108 * here verifier looks at prototype of map_lookup_elem() and sees: 109 * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok, 110 * Now verifier knows that this map has key of R1->map_ptr->key_size bytes 111 * 112 * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far, 113 * Now verifier checks that [R2, R2 + map's key_size) are within stack limits 114 * and were initialized prior to this call. 115 * If it's ok, then verifier allows this BPF_CALL insn and looks at 116 * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets 117 * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function 118 * returns ether pointer to map value or NULL. 119 * 120 * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off' 121 * insn, the register holding that pointer in the true branch changes state to 122 * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false 123 * branch. See check_cond_jmp_op(). 124 * 125 * After the call R0 is set to return type of the function and registers R1-R5 126 * are set to NOT_INIT to indicate that they are no longer readable. 127 */ 128 129 struct reg_state { 130 enum bpf_reg_type type; 131 union { 132 /* valid when type == CONST_IMM | PTR_TO_STACK | UNKNOWN_VALUE */ 133 s64 imm; 134 135 /* valid when type == PTR_TO_PACKET* */ 136 struct { 137 u32 id; 138 u16 off; 139 u16 range; 140 }; 141 142 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE | 143 * PTR_TO_MAP_VALUE_OR_NULL 144 */ 145 struct bpf_map *map_ptr; 146 }; 147 }; 148 149 enum bpf_stack_slot_type { 150 STACK_INVALID, /* nothing was stored in this stack slot */ 151 STACK_SPILL, /* register spilled into stack */ 152 STACK_MISC /* BPF program wrote some data into this slot */ 153 }; 154 155 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */ 156 157 /* state of the program: 158 * type of all registers and stack info 159 */ 160 struct verifier_state { 161 struct reg_state regs[MAX_BPF_REG]; 162 u8 stack_slot_type[MAX_BPF_STACK]; 163 struct reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE]; 164 }; 165 166 /* linked list of verifier states used to prune search */ 167 struct verifier_state_list { 168 struct verifier_state state; 169 struct verifier_state_list *next; 170 }; 171 172 /* verifier_state + insn_idx are pushed to stack when branch is encountered */ 173 struct verifier_stack_elem { 174 /* verifer state is 'st' 175 * before processing instruction 'insn_idx' 176 * and after processing instruction 'prev_insn_idx' 177 */ 178 struct verifier_state st; 179 int insn_idx; 180 int prev_insn_idx; 181 struct verifier_stack_elem *next; 182 }; 183 184 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */ 185 186 /* single container for all structs 187 * one verifier_env per bpf_check() call 188 */ 189 struct verifier_env { 190 struct bpf_prog *prog; /* eBPF program being verified */ 191 struct verifier_stack_elem *head; /* stack of verifier states to be processed */ 192 int stack_size; /* number of states to be processed */ 193 struct verifier_state cur_state; /* current verifier state */ 194 struct verifier_state_list **explored_states; /* search pruning optimization */ 195 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */ 196 u32 used_map_cnt; /* number of used maps */ 197 u32 id_gen; /* used to generate unique reg IDs */ 198 bool allow_ptr_leaks; 199 }; 200 201 #define BPF_COMPLEXITY_LIMIT_INSNS 65536 202 #define BPF_COMPLEXITY_LIMIT_STACK 1024 203 204 struct bpf_call_arg_meta { 205 struct bpf_map *map_ptr; 206 bool raw_mode; 207 int regno; 208 int access_size; 209 }; 210 211 /* verbose verifier prints what it's seeing 212 * bpf_check() is called under lock, so no race to access these global vars 213 */ 214 static u32 log_level, log_size, log_len; 215 static char *log_buf; 216 217 static DEFINE_MUTEX(bpf_verifier_lock); 218 219 /* log_level controls verbosity level of eBPF verifier. 220 * verbose() is used to dump the verification trace to the log, so the user 221 * can figure out what's wrong with the program 222 */ 223 static __printf(1, 2) void verbose(const char *fmt, ...) 224 { 225 va_list args; 226 227 if (log_level == 0 || log_len >= log_size - 1) 228 return; 229 230 va_start(args, fmt); 231 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args); 232 va_end(args); 233 } 234 235 /* string representation of 'enum bpf_reg_type' */ 236 static const char * const reg_type_str[] = { 237 [NOT_INIT] = "?", 238 [UNKNOWN_VALUE] = "inv", 239 [PTR_TO_CTX] = "ctx", 240 [CONST_PTR_TO_MAP] = "map_ptr", 241 [PTR_TO_MAP_VALUE] = "map_value", 242 [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null", 243 [FRAME_PTR] = "fp", 244 [PTR_TO_STACK] = "fp", 245 [CONST_IMM] = "imm", 246 [PTR_TO_PACKET] = "pkt", 247 [PTR_TO_PACKET_END] = "pkt_end", 248 }; 249 250 static void print_verifier_state(struct verifier_state *state) 251 { 252 struct reg_state *reg; 253 enum bpf_reg_type t; 254 int i; 255 256 for (i = 0; i < MAX_BPF_REG; i++) { 257 reg = &state->regs[i]; 258 t = reg->type; 259 if (t == NOT_INIT) 260 continue; 261 verbose(" R%d=%s", i, reg_type_str[t]); 262 if (t == CONST_IMM || t == PTR_TO_STACK) 263 verbose("%lld", reg->imm); 264 else if (t == PTR_TO_PACKET) 265 verbose("(id=%d,off=%d,r=%d)", 266 reg->id, reg->off, reg->range); 267 else if (t == UNKNOWN_VALUE && reg->imm) 268 verbose("%lld", reg->imm); 269 else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE || 270 t == PTR_TO_MAP_VALUE_OR_NULL) 271 verbose("(ks=%d,vs=%d)", 272 reg->map_ptr->key_size, 273 reg->map_ptr->value_size); 274 } 275 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 276 if (state->stack_slot_type[i] == STACK_SPILL) 277 verbose(" fp%d=%s", -MAX_BPF_STACK + i, 278 reg_type_str[state->spilled_regs[i / BPF_REG_SIZE].type]); 279 } 280 verbose("\n"); 281 } 282 283 static const char *const bpf_class_string[] = { 284 [BPF_LD] = "ld", 285 [BPF_LDX] = "ldx", 286 [BPF_ST] = "st", 287 [BPF_STX] = "stx", 288 [BPF_ALU] = "alu", 289 [BPF_JMP] = "jmp", 290 [BPF_RET] = "BUG", 291 [BPF_ALU64] = "alu64", 292 }; 293 294 static const char *const bpf_alu_string[16] = { 295 [BPF_ADD >> 4] = "+=", 296 [BPF_SUB >> 4] = "-=", 297 [BPF_MUL >> 4] = "*=", 298 [BPF_DIV >> 4] = "/=", 299 [BPF_OR >> 4] = "|=", 300 [BPF_AND >> 4] = "&=", 301 [BPF_LSH >> 4] = "<<=", 302 [BPF_RSH >> 4] = ">>=", 303 [BPF_NEG >> 4] = "neg", 304 [BPF_MOD >> 4] = "%=", 305 [BPF_XOR >> 4] = "^=", 306 [BPF_MOV >> 4] = "=", 307 [BPF_ARSH >> 4] = "s>>=", 308 [BPF_END >> 4] = "endian", 309 }; 310 311 static const char *const bpf_ldst_string[] = { 312 [BPF_W >> 3] = "u32", 313 [BPF_H >> 3] = "u16", 314 [BPF_B >> 3] = "u8", 315 [BPF_DW >> 3] = "u64", 316 }; 317 318 static const char *const bpf_jmp_string[16] = { 319 [BPF_JA >> 4] = "jmp", 320 [BPF_JEQ >> 4] = "==", 321 [BPF_JGT >> 4] = ">", 322 [BPF_JGE >> 4] = ">=", 323 [BPF_JSET >> 4] = "&", 324 [BPF_JNE >> 4] = "!=", 325 [BPF_JSGT >> 4] = "s>", 326 [BPF_JSGE >> 4] = "s>=", 327 [BPF_CALL >> 4] = "call", 328 [BPF_EXIT >> 4] = "exit", 329 }; 330 331 static void print_bpf_insn(struct bpf_insn *insn) 332 { 333 u8 class = BPF_CLASS(insn->code); 334 335 if (class == BPF_ALU || class == BPF_ALU64) { 336 if (BPF_SRC(insn->code) == BPF_X) 337 verbose("(%02x) %sr%d %s %sr%d\n", 338 insn->code, class == BPF_ALU ? "(u32) " : "", 339 insn->dst_reg, 340 bpf_alu_string[BPF_OP(insn->code) >> 4], 341 class == BPF_ALU ? "(u32) " : "", 342 insn->src_reg); 343 else 344 verbose("(%02x) %sr%d %s %s%d\n", 345 insn->code, class == BPF_ALU ? "(u32) " : "", 346 insn->dst_reg, 347 bpf_alu_string[BPF_OP(insn->code) >> 4], 348 class == BPF_ALU ? "(u32) " : "", 349 insn->imm); 350 } else if (class == BPF_STX) { 351 if (BPF_MODE(insn->code) == BPF_MEM) 352 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n", 353 insn->code, 354 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 355 insn->dst_reg, 356 insn->off, insn->src_reg); 357 else if (BPF_MODE(insn->code) == BPF_XADD) 358 verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n", 359 insn->code, 360 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 361 insn->dst_reg, insn->off, 362 insn->src_reg); 363 else 364 verbose("BUG_%02x\n", insn->code); 365 } else if (class == BPF_ST) { 366 if (BPF_MODE(insn->code) != BPF_MEM) { 367 verbose("BUG_st_%02x\n", insn->code); 368 return; 369 } 370 verbose("(%02x) *(%s *)(r%d %+d) = %d\n", 371 insn->code, 372 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 373 insn->dst_reg, 374 insn->off, insn->imm); 375 } else if (class == BPF_LDX) { 376 if (BPF_MODE(insn->code) != BPF_MEM) { 377 verbose("BUG_ldx_%02x\n", insn->code); 378 return; 379 } 380 verbose("(%02x) r%d = *(%s *)(r%d %+d)\n", 381 insn->code, insn->dst_reg, 382 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 383 insn->src_reg, insn->off); 384 } else if (class == BPF_LD) { 385 if (BPF_MODE(insn->code) == BPF_ABS) { 386 verbose("(%02x) r0 = *(%s *)skb[%d]\n", 387 insn->code, 388 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 389 insn->imm); 390 } else if (BPF_MODE(insn->code) == BPF_IND) { 391 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n", 392 insn->code, 393 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 394 insn->src_reg, insn->imm); 395 } else if (BPF_MODE(insn->code) == BPF_IMM) { 396 verbose("(%02x) r%d = 0x%x\n", 397 insn->code, insn->dst_reg, insn->imm); 398 } else { 399 verbose("BUG_ld_%02x\n", insn->code); 400 return; 401 } 402 } else if (class == BPF_JMP) { 403 u8 opcode = BPF_OP(insn->code); 404 405 if (opcode == BPF_CALL) { 406 verbose("(%02x) call %d\n", insn->code, insn->imm); 407 } else if (insn->code == (BPF_JMP | BPF_JA)) { 408 verbose("(%02x) goto pc%+d\n", 409 insn->code, insn->off); 410 } else if (insn->code == (BPF_JMP | BPF_EXIT)) { 411 verbose("(%02x) exit\n", insn->code); 412 } else if (BPF_SRC(insn->code) == BPF_X) { 413 verbose("(%02x) if r%d %s r%d goto pc%+d\n", 414 insn->code, insn->dst_reg, 415 bpf_jmp_string[BPF_OP(insn->code) >> 4], 416 insn->src_reg, insn->off); 417 } else { 418 verbose("(%02x) if r%d %s 0x%x goto pc%+d\n", 419 insn->code, insn->dst_reg, 420 bpf_jmp_string[BPF_OP(insn->code) >> 4], 421 insn->imm, insn->off); 422 } 423 } else { 424 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]); 425 } 426 } 427 428 static int pop_stack(struct verifier_env *env, int *prev_insn_idx) 429 { 430 struct verifier_stack_elem *elem; 431 int insn_idx; 432 433 if (env->head == NULL) 434 return -1; 435 436 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state)); 437 insn_idx = env->head->insn_idx; 438 if (prev_insn_idx) 439 *prev_insn_idx = env->head->prev_insn_idx; 440 elem = env->head->next; 441 kfree(env->head); 442 env->head = elem; 443 env->stack_size--; 444 return insn_idx; 445 } 446 447 static struct verifier_state *push_stack(struct verifier_env *env, int insn_idx, 448 int prev_insn_idx) 449 { 450 struct verifier_stack_elem *elem; 451 452 elem = kmalloc(sizeof(struct verifier_stack_elem), GFP_KERNEL); 453 if (!elem) 454 goto err; 455 456 memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state)); 457 elem->insn_idx = insn_idx; 458 elem->prev_insn_idx = prev_insn_idx; 459 elem->next = env->head; 460 env->head = elem; 461 env->stack_size++; 462 if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) { 463 verbose("BPF program is too complex\n"); 464 goto err; 465 } 466 return &elem->st; 467 err: 468 /* pop all elements and return */ 469 while (pop_stack(env, NULL) >= 0); 470 return NULL; 471 } 472 473 #define CALLER_SAVED_REGS 6 474 static const int caller_saved[CALLER_SAVED_REGS] = { 475 BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5 476 }; 477 478 static void init_reg_state(struct reg_state *regs) 479 { 480 int i; 481 482 for (i = 0; i < MAX_BPF_REG; i++) { 483 regs[i].type = NOT_INIT; 484 regs[i].imm = 0; 485 } 486 487 /* frame pointer */ 488 regs[BPF_REG_FP].type = FRAME_PTR; 489 490 /* 1st arg to a function */ 491 regs[BPF_REG_1].type = PTR_TO_CTX; 492 } 493 494 static void mark_reg_unknown_value(struct reg_state *regs, u32 regno) 495 { 496 BUG_ON(regno >= MAX_BPF_REG); 497 regs[regno].type = UNKNOWN_VALUE; 498 regs[regno].imm = 0; 499 } 500 501 enum reg_arg_type { 502 SRC_OP, /* register is used as source operand */ 503 DST_OP, /* register is used as destination operand */ 504 DST_OP_NO_MARK /* same as above, check only, don't mark */ 505 }; 506 507 static int check_reg_arg(struct reg_state *regs, u32 regno, 508 enum reg_arg_type t) 509 { 510 if (regno >= MAX_BPF_REG) { 511 verbose("R%d is invalid\n", regno); 512 return -EINVAL; 513 } 514 515 if (t == SRC_OP) { 516 /* check whether register used as source operand can be read */ 517 if (regs[regno].type == NOT_INIT) { 518 verbose("R%d !read_ok\n", regno); 519 return -EACCES; 520 } 521 } else { 522 /* check whether register used as dest operand can be written to */ 523 if (regno == BPF_REG_FP) { 524 verbose("frame pointer is read only\n"); 525 return -EACCES; 526 } 527 if (t == DST_OP) 528 mark_reg_unknown_value(regs, regno); 529 } 530 return 0; 531 } 532 533 static int bpf_size_to_bytes(int bpf_size) 534 { 535 if (bpf_size == BPF_W) 536 return 4; 537 else if (bpf_size == BPF_H) 538 return 2; 539 else if (bpf_size == BPF_B) 540 return 1; 541 else if (bpf_size == BPF_DW) 542 return 8; 543 else 544 return -EINVAL; 545 } 546 547 static bool is_spillable_regtype(enum bpf_reg_type type) 548 { 549 switch (type) { 550 case PTR_TO_MAP_VALUE: 551 case PTR_TO_MAP_VALUE_OR_NULL: 552 case PTR_TO_STACK: 553 case PTR_TO_CTX: 554 case PTR_TO_PACKET: 555 case PTR_TO_PACKET_END: 556 case FRAME_PTR: 557 case CONST_PTR_TO_MAP: 558 return true; 559 default: 560 return false; 561 } 562 } 563 564 /* check_stack_read/write functions track spill/fill of registers, 565 * stack boundary and alignment are checked in check_mem_access() 566 */ 567 static int check_stack_write(struct verifier_state *state, int off, int size, 568 int value_regno) 569 { 570 int i; 571 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0, 572 * so it's aligned access and [off, off + size) are within stack limits 573 */ 574 575 if (value_regno >= 0 && 576 is_spillable_regtype(state->regs[value_regno].type)) { 577 578 /* register containing pointer is being spilled into stack */ 579 if (size != BPF_REG_SIZE) { 580 verbose("invalid size of register spill\n"); 581 return -EACCES; 582 } 583 584 /* save register state */ 585 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = 586 state->regs[value_regno]; 587 588 for (i = 0; i < BPF_REG_SIZE; i++) 589 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL; 590 } else { 591 /* regular write of data into stack */ 592 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = 593 (struct reg_state) {}; 594 595 for (i = 0; i < size; i++) 596 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC; 597 } 598 return 0; 599 } 600 601 static int check_stack_read(struct verifier_state *state, int off, int size, 602 int value_regno) 603 { 604 u8 *slot_type; 605 int i; 606 607 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off]; 608 609 if (slot_type[0] == STACK_SPILL) { 610 if (size != BPF_REG_SIZE) { 611 verbose("invalid size of register spill\n"); 612 return -EACCES; 613 } 614 for (i = 1; i < BPF_REG_SIZE; i++) { 615 if (slot_type[i] != STACK_SPILL) { 616 verbose("corrupted spill memory\n"); 617 return -EACCES; 618 } 619 } 620 621 if (value_regno >= 0) 622 /* restore register state from stack */ 623 state->regs[value_regno] = 624 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE]; 625 return 0; 626 } else { 627 for (i = 0; i < size; i++) { 628 if (slot_type[i] != STACK_MISC) { 629 verbose("invalid read from stack off %d+%d size %d\n", 630 off, i, size); 631 return -EACCES; 632 } 633 } 634 if (value_regno >= 0) 635 /* have read misc data from the stack */ 636 mark_reg_unknown_value(state->regs, value_regno); 637 return 0; 638 } 639 } 640 641 /* check read/write into map element returned by bpf_map_lookup_elem() */ 642 static int check_map_access(struct verifier_env *env, u32 regno, int off, 643 int size) 644 { 645 struct bpf_map *map = env->cur_state.regs[regno].map_ptr; 646 647 if (off < 0 || off + size > map->value_size) { 648 verbose("invalid access to map value, value_size=%d off=%d size=%d\n", 649 map->value_size, off, size); 650 return -EACCES; 651 } 652 return 0; 653 } 654 655 #define MAX_PACKET_OFF 0xffff 656 657 static bool may_write_pkt_data(enum bpf_prog_type type) 658 { 659 switch (type) { 660 case BPF_PROG_TYPE_XDP: 661 return true; 662 default: 663 return false; 664 } 665 } 666 667 static int check_packet_access(struct verifier_env *env, u32 regno, int off, 668 int size) 669 { 670 struct reg_state *regs = env->cur_state.regs; 671 struct reg_state *reg = ®s[regno]; 672 673 off += reg->off; 674 if (off < 0 || off + size > reg->range) { 675 verbose("invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n", 676 off, size, regno, reg->id, reg->off, reg->range); 677 return -EACCES; 678 } 679 return 0; 680 } 681 682 /* check access to 'struct bpf_context' fields */ 683 static int check_ctx_access(struct verifier_env *env, int off, int size, 684 enum bpf_access_type t, enum bpf_reg_type *reg_type) 685 { 686 if (env->prog->aux->ops->is_valid_access && 687 env->prog->aux->ops->is_valid_access(off, size, t, reg_type)) { 688 /* remember the offset of last byte accessed in ctx */ 689 if (env->prog->aux->max_ctx_offset < off + size) 690 env->prog->aux->max_ctx_offset = off + size; 691 return 0; 692 } 693 694 verbose("invalid bpf_context access off=%d size=%d\n", off, size); 695 return -EACCES; 696 } 697 698 static bool is_pointer_value(struct verifier_env *env, int regno) 699 { 700 if (env->allow_ptr_leaks) 701 return false; 702 703 switch (env->cur_state.regs[regno].type) { 704 case UNKNOWN_VALUE: 705 case CONST_IMM: 706 return false; 707 default: 708 return true; 709 } 710 } 711 712 static int check_ptr_alignment(struct verifier_env *env, struct reg_state *reg, 713 int off, int size) 714 { 715 if (reg->type != PTR_TO_PACKET) { 716 if (off % size != 0) { 717 verbose("misaligned access off %d size %d\n", off, size); 718 return -EACCES; 719 } else { 720 return 0; 721 } 722 } 723 724 switch (env->prog->type) { 725 case BPF_PROG_TYPE_SCHED_CLS: 726 case BPF_PROG_TYPE_SCHED_ACT: 727 case BPF_PROG_TYPE_XDP: 728 break; 729 default: 730 verbose("verifier is misconfigured\n"); 731 return -EACCES; 732 } 733 734 if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) 735 /* misaligned access to packet is ok on x86,arm,arm64 */ 736 return 0; 737 738 if (reg->id && size != 1) { 739 verbose("Unknown packet alignment. Only byte-sized access allowed\n"); 740 return -EACCES; 741 } 742 743 /* skb->data is NET_IP_ALIGN-ed */ 744 if ((NET_IP_ALIGN + reg->off + off) % size != 0) { 745 verbose("misaligned packet access off %d+%d+%d size %d\n", 746 NET_IP_ALIGN, reg->off, off, size); 747 return -EACCES; 748 } 749 return 0; 750 } 751 752 /* check whether memory at (regno + off) is accessible for t = (read | write) 753 * if t==write, value_regno is a register which value is stored into memory 754 * if t==read, value_regno is a register which will receive the value from memory 755 * if t==write && value_regno==-1, some unknown value is stored into memory 756 * if t==read && value_regno==-1, don't care what we read from memory 757 */ 758 static int check_mem_access(struct verifier_env *env, u32 regno, int off, 759 int bpf_size, enum bpf_access_type t, 760 int value_regno) 761 { 762 struct verifier_state *state = &env->cur_state; 763 struct reg_state *reg = &state->regs[regno]; 764 int size, err = 0; 765 766 if (reg->type == PTR_TO_STACK) 767 off += reg->imm; 768 769 size = bpf_size_to_bytes(bpf_size); 770 if (size < 0) 771 return size; 772 773 err = check_ptr_alignment(env, reg, off, size); 774 if (err) 775 return err; 776 777 if (reg->type == PTR_TO_MAP_VALUE) { 778 if (t == BPF_WRITE && value_regno >= 0 && 779 is_pointer_value(env, value_regno)) { 780 verbose("R%d leaks addr into map\n", value_regno); 781 return -EACCES; 782 } 783 err = check_map_access(env, regno, off, size); 784 if (!err && t == BPF_READ && value_regno >= 0) 785 mark_reg_unknown_value(state->regs, value_regno); 786 787 } else if (reg->type == PTR_TO_CTX) { 788 enum bpf_reg_type reg_type = UNKNOWN_VALUE; 789 790 if (t == BPF_WRITE && value_regno >= 0 && 791 is_pointer_value(env, value_regno)) { 792 verbose("R%d leaks addr into ctx\n", value_regno); 793 return -EACCES; 794 } 795 err = check_ctx_access(env, off, size, t, ®_type); 796 if (!err && t == BPF_READ && value_regno >= 0) { 797 mark_reg_unknown_value(state->regs, value_regno); 798 if (env->allow_ptr_leaks) 799 /* note that reg.[id|off|range] == 0 */ 800 state->regs[value_regno].type = reg_type; 801 } 802 803 } else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) { 804 if (off >= 0 || off < -MAX_BPF_STACK) { 805 verbose("invalid stack off=%d size=%d\n", off, size); 806 return -EACCES; 807 } 808 if (t == BPF_WRITE) { 809 if (!env->allow_ptr_leaks && 810 state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL && 811 size != BPF_REG_SIZE) { 812 verbose("attempt to corrupt spilled pointer on stack\n"); 813 return -EACCES; 814 } 815 err = check_stack_write(state, off, size, value_regno); 816 } else { 817 err = check_stack_read(state, off, size, value_regno); 818 } 819 } else if (state->regs[regno].type == PTR_TO_PACKET) { 820 if (t == BPF_WRITE && !may_write_pkt_data(env->prog->type)) { 821 verbose("cannot write into packet\n"); 822 return -EACCES; 823 } 824 if (t == BPF_WRITE && value_regno >= 0 && 825 is_pointer_value(env, value_regno)) { 826 verbose("R%d leaks addr into packet\n", value_regno); 827 return -EACCES; 828 } 829 err = check_packet_access(env, regno, off, size); 830 if (!err && t == BPF_READ && value_regno >= 0) 831 mark_reg_unknown_value(state->regs, value_regno); 832 } else { 833 verbose("R%d invalid mem access '%s'\n", 834 regno, reg_type_str[reg->type]); 835 return -EACCES; 836 } 837 838 if (!err && size <= 2 && value_regno >= 0 && env->allow_ptr_leaks && 839 state->regs[value_regno].type == UNKNOWN_VALUE) { 840 /* 1 or 2 byte load zero-extends, determine the number of 841 * zero upper bits. Not doing it fo 4 byte load, since 842 * such values cannot be added to ptr_to_packet anyway. 843 */ 844 state->regs[value_regno].imm = 64 - size * 8; 845 } 846 return err; 847 } 848 849 static int check_xadd(struct verifier_env *env, struct bpf_insn *insn) 850 { 851 struct reg_state *regs = env->cur_state.regs; 852 int err; 853 854 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) || 855 insn->imm != 0) { 856 verbose("BPF_XADD uses reserved fields\n"); 857 return -EINVAL; 858 } 859 860 /* check src1 operand */ 861 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 862 if (err) 863 return err; 864 865 /* check src2 operand */ 866 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 867 if (err) 868 return err; 869 870 /* check whether atomic_add can read the memory */ 871 err = check_mem_access(env, insn->dst_reg, insn->off, 872 BPF_SIZE(insn->code), BPF_READ, -1); 873 if (err) 874 return err; 875 876 /* check whether atomic_add can write into the same memory */ 877 return check_mem_access(env, insn->dst_reg, insn->off, 878 BPF_SIZE(insn->code), BPF_WRITE, -1); 879 } 880 881 /* when register 'regno' is passed into function that will read 'access_size' 882 * bytes from that pointer, make sure that it's within stack boundary 883 * and all elements of stack are initialized 884 */ 885 static int check_stack_boundary(struct verifier_env *env, int regno, 886 int access_size, bool zero_size_allowed, 887 struct bpf_call_arg_meta *meta) 888 { 889 struct verifier_state *state = &env->cur_state; 890 struct reg_state *regs = state->regs; 891 int off, i; 892 893 if (regs[regno].type != PTR_TO_STACK) { 894 if (zero_size_allowed && access_size == 0 && 895 regs[regno].type == CONST_IMM && 896 regs[regno].imm == 0) 897 return 0; 898 899 verbose("R%d type=%s expected=%s\n", regno, 900 reg_type_str[regs[regno].type], 901 reg_type_str[PTR_TO_STACK]); 902 return -EACCES; 903 } 904 905 off = regs[regno].imm; 906 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 || 907 access_size <= 0) { 908 verbose("invalid stack type R%d off=%d access_size=%d\n", 909 regno, off, access_size); 910 return -EACCES; 911 } 912 913 if (meta && meta->raw_mode) { 914 meta->access_size = access_size; 915 meta->regno = regno; 916 return 0; 917 } 918 919 for (i = 0; i < access_size; i++) { 920 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) { 921 verbose("invalid indirect read from stack off %d+%d size %d\n", 922 off, i, access_size); 923 return -EACCES; 924 } 925 } 926 return 0; 927 } 928 929 static int check_func_arg(struct verifier_env *env, u32 regno, 930 enum bpf_arg_type arg_type, 931 struct bpf_call_arg_meta *meta) 932 { 933 struct reg_state *reg = env->cur_state.regs + regno; 934 enum bpf_reg_type expected_type; 935 int err = 0; 936 937 if (arg_type == ARG_DONTCARE) 938 return 0; 939 940 if (reg->type == NOT_INIT) { 941 verbose("R%d !read_ok\n", regno); 942 return -EACCES; 943 } 944 945 if (arg_type == ARG_ANYTHING) { 946 if (is_pointer_value(env, regno)) { 947 verbose("R%d leaks addr into helper function\n", regno); 948 return -EACCES; 949 } 950 return 0; 951 } 952 953 if (arg_type == ARG_PTR_TO_MAP_KEY || 954 arg_type == ARG_PTR_TO_MAP_VALUE) { 955 expected_type = PTR_TO_STACK; 956 } else if (arg_type == ARG_CONST_STACK_SIZE || 957 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) { 958 expected_type = CONST_IMM; 959 } else if (arg_type == ARG_CONST_MAP_PTR) { 960 expected_type = CONST_PTR_TO_MAP; 961 } else if (arg_type == ARG_PTR_TO_CTX) { 962 expected_type = PTR_TO_CTX; 963 } else if (arg_type == ARG_PTR_TO_STACK || 964 arg_type == ARG_PTR_TO_RAW_STACK) { 965 expected_type = PTR_TO_STACK; 966 /* One exception here. In case function allows for NULL to be 967 * passed in as argument, it's a CONST_IMM type. Final test 968 * happens during stack boundary checking. 969 */ 970 if (reg->type == CONST_IMM && reg->imm == 0) 971 expected_type = CONST_IMM; 972 meta->raw_mode = arg_type == ARG_PTR_TO_RAW_STACK; 973 } else { 974 verbose("unsupported arg_type %d\n", arg_type); 975 return -EFAULT; 976 } 977 978 if (reg->type != expected_type) { 979 verbose("R%d type=%s expected=%s\n", regno, 980 reg_type_str[reg->type], reg_type_str[expected_type]); 981 return -EACCES; 982 } 983 984 if (arg_type == ARG_CONST_MAP_PTR) { 985 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */ 986 meta->map_ptr = reg->map_ptr; 987 } else if (arg_type == ARG_PTR_TO_MAP_KEY) { 988 /* bpf_map_xxx(..., map_ptr, ..., key) call: 989 * check that [key, key + map->key_size) are within 990 * stack limits and initialized 991 */ 992 if (!meta->map_ptr) { 993 /* in function declaration map_ptr must come before 994 * map_key, so that it's verified and known before 995 * we have to check map_key here. Otherwise it means 996 * that kernel subsystem misconfigured verifier 997 */ 998 verbose("invalid map_ptr to access map->key\n"); 999 return -EACCES; 1000 } 1001 err = check_stack_boundary(env, regno, meta->map_ptr->key_size, 1002 false, NULL); 1003 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) { 1004 /* bpf_map_xxx(..., map_ptr, ..., value) call: 1005 * check [value, value + map->value_size) validity 1006 */ 1007 if (!meta->map_ptr) { 1008 /* kernel subsystem misconfigured verifier */ 1009 verbose("invalid map_ptr to access map->value\n"); 1010 return -EACCES; 1011 } 1012 err = check_stack_boundary(env, regno, 1013 meta->map_ptr->value_size, 1014 false, NULL); 1015 } else if (arg_type == ARG_CONST_STACK_SIZE || 1016 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) { 1017 bool zero_size_allowed = (arg_type == ARG_CONST_STACK_SIZE_OR_ZERO); 1018 1019 /* bpf_xxx(..., buf, len) call will access 'len' bytes 1020 * from stack pointer 'buf'. Check it 1021 * note: regno == len, regno - 1 == buf 1022 */ 1023 if (regno == 0) { 1024 /* kernel subsystem misconfigured verifier */ 1025 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n"); 1026 return -EACCES; 1027 } 1028 err = check_stack_boundary(env, regno - 1, reg->imm, 1029 zero_size_allowed, meta); 1030 } 1031 1032 return err; 1033 } 1034 1035 static int check_map_func_compatibility(struct bpf_map *map, int func_id) 1036 { 1037 if (!map) 1038 return 0; 1039 1040 /* We need a two way check, first is from map perspective ... */ 1041 switch (map->map_type) { 1042 case BPF_MAP_TYPE_PROG_ARRAY: 1043 if (func_id != BPF_FUNC_tail_call) 1044 goto error; 1045 break; 1046 case BPF_MAP_TYPE_PERF_EVENT_ARRAY: 1047 if (func_id != BPF_FUNC_perf_event_read && 1048 func_id != BPF_FUNC_perf_event_output) 1049 goto error; 1050 break; 1051 case BPF_MAP_TYPE_STACK_TRACE: 1052 if (func_id != BPF_FUNC_get_stackid) 1053 goto error; 1054 break; 1055 case BPF_MAP_TYPE_CGROUP_ARRAY: 1056 if (func_id != BPF_FUNC_skb_under_cgroup) 1057 goto error; 1058 break; 1059 default: 1060 break; 1061 } 1062 1063 /* ... and second from the function itself. */ 1064 switch (func_id) { 1065 case BPF_FUNC_tail_call: 1066 if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY) 1067 goto error; 1068 break; 1069 case BPF_FUNC_perf_event_read: 1070 case BPF_FUNC_perf_event_output: 1071 if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY) 1072 goto error; 1073 break; 1074 case BPF_FUNC_get_stackid: 1075 if (map->map_type != BPF_MAP_TYPE_STACK_TRACE) 1076 goto error; 1077 break; 1078 case BPF_FUNC_skb_under_cgroup: 1079 if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY) 1080 goto error; 1081 break; 1082 default: 1083 break; 1084 } 1085 1086 return 0; 1087 error: 1088 verbose("cannot pass map_type %d into func %d\n", 1089 map->map_type, func_id); 1090 return -EINVAL; 1091 } 1092 1093 static int check_raw_mode(const struct bpf_func_proto *fn) 1094 { 1095 int count = 0; 1096 1097 if (fn->arg1_type == ARG_PTR_TO_RAW_STACK) 1098 count++; 1099 if (fn->arg2_type == ARG_PTR_TO_RAW_STACK) 1100 count++; 1101 if (fn->arg3_type == ARG_PTR_TO_RAW_STACK) 1102 count++; 1103 if (fn->arg4_type == ARG_PTR_TO_RAW_STACK) 1104 count++; 1105 if (fn->arg5_type == ARG_PTR_TO_RAW_STACK) 1106 count++; 1107 1108 return count > 1 ? -EINVAL : 0; 1109 } 1110 1111 static void clear_all_pkt_pointers(struct verifier_env *env) 1112 { 1113 struct verifier_state *state = &env->cur_state; 1114 struct reg_state *regs = state->regs, *reg; 1115 int i; 1116 1117 for (i = 0; i < MAX_BPF_REG; i++) 1118 if (regs[i].type == PTR_TO_PACKET || 1119 regs[i].type == PTR_TO_PACKET_END) 1120 mark_reg_unknown_value(regs, i); 1121 1122 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 1123 if (state->stack_slot_type[i] != STACK_SPILL) 1124 continue; 1125 reg = &state->spilled_regs[i / BPF_REG_SIZE]; 1126 if (reg->type != PTR_TO_PACKET && 1127 reg->type != PTR_TO_PACKET_END) 1128 continue; 1129 reg->type = UNKNOWN_VALUE; 1130 reg->imm = 0; 1131 } 1132 } 1133 1134 static int check_call(struct verifier_env *env, int func_id) 1135 { 1136 struct verifier_state *state = &env->cur_state; 1137 const struct bpf_func_proto *fn = NULL; 1138 struct reg_state *regs = state->regs; 1139 struct reg_state *reg; 1140 struct bpf_call_arg_meta meta; 1141 bool changes_data; 1142 int i, err; 1143 1144 /* find function prototype */ 1145 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) { 1146 verbose("invalid func %d\n", func_id); 1147 return -EINVAL; 1148 } 1149 1150 if (env->prog->aux->ops->get_func_proto) 1151 fn = env->prog->aux->ops->get_func_proto(func_id); 1152 1153 if (!fn) { 1154 verbose("unknown func %d\n", func_id); 1155 return -EINVAL; 1156 } 1157 1158 /* eBPF programs must be GPL compatible to use GPL-ed functions */ 1159 if (!env->prog->gpl_compatible && fn->gpl_only) { 1160 verbose("cannot call GPL only function from proprietary program\n"); 1161 return -EINVAL; 1162 } 1163 1164 changes_data = bpf_helper_changes_skb_data(fn->func); 1165 1166 memset(&meta, 0, sizeof(meta)); 1167 1168 /* We only support one arg being in raw mode at the moment, which 1169 * is sufficient for the helper functions we have right now. 1170 */ 1171 err = check_raw_mode(fn); 1172 if (err) { 1173 verbose("kernel subsystem misconfigured func %d\n", func_id); 1174 return err; 1175 } 1176 1177 /* check args */ 1178 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta); 1179 if (err) 1180 return err; 1181 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta); 1182 if (err) 1183 return err; 1184 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta); 1185 if (err) 1186 return err; 1187 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta); 1188 if (err) 1189 return err; 1190 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta); 1191 if (err) 1192 return err; 1193 1194 /* Mark slots with STACK_MISC in case of raw mode, stack offset 1195 * is inferred from register state. 1196 */ 1197 for (i = 0; i < meta.access_size; i++) { 1198 err = check_mem_access(env, meta.regno, i, BPF_B, BPF_WRITE, -1); 1199 if (err) 1200 return err; 1201 } 1202 1203 /* reset caller saved regs */ 1204 for (i = 0; i < CALLER_SAVED_REGS; i++) { 1205 reg = regs + caller_saved[i]; 1206 reg->type = NOT_INIT; 1207 reg->imm = 0; 1208 } 1209 1210 /* update return register */ 1211 if (fn->ret_type == RET_INTEGER) { 1212 regs[BPF_REG_0].type = UNKNOWN_VALUE; 1213 } else if (fn->ret_type == RET_VOID) { 1214 regs[BPF_REG_0].type = NOT_INIT; 1215 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) { 1216 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL; 1217 /* remember map_ptr, so that check_map_access() 1218 * can check 'value_size' boundary of memory access 1219 * to map element returned from bpf_map_lookup_elem() 1220 */ 1221 if (meta.map_ptr == NULL) { 1222 verbose("kernel subsystem misconfigured verifier\n"); 1223 return -EINVAL; 1224 } 1225 regs[BPF_REG_0].map_ptr = meta.map_ptr; 1226 } else { 1227 verbose("unknown return type %d of func %d\n", 1228 fn->ret_type, func_id); 1229 return -EINVAL; 1230 } 1231 1232 err = check_map_func_compatibility(meta.map_ptr, func_id); 1233 if (err) 1234 return err; 1235 1236 if (changes_data) 1237 clear_all_pkt_pointers(env); 1238 return 0; 1239 } 1240 1241 static int check_packet_ptr_add(struct verifier_env *env, struct bpf_insn *insn) 1242 { 1243 struct reg_state *regs = env->cur_state.regs; 1244 struct reg_state *dst_reg = ®s[insn->dst_reg]; 1245 struct reg_state *src_reg = ®s[insn->src_reg]; 1246 struct reg_state tmp_reg; 1247 s32 imm; 1248 1249 if (BPF_SRC(insn->code) == BPF_K) { 1250 /* pkt_ptr += imm */ 1251 imm = insn->imm; 1252 1253 add_imm: 1254 if (imm <= 0) { 1255 verbose("addition of negative constant to packet pointer is not allowed\n"); 1256 return -EACCES; 1257 } 1258 if (imm >= MAX_PACKET_OFF || 1259 imm + dst_reg->off >= MAX_PACKET_OFF) { 1260 verbose("constant %d is too large to add to packet pointer\n", 1261 imm); 1262 return -EACCES; 1263 } 1264 /* a constant was added to pkt_ptr. 1265 * Remember it while keeping the same 'id' 1266 */ 1267 dst_reg->off += imm; 1268 } else { 1269 if (src_reg->type == PTR_TO_PACKET) { 1270 /* R6=pkt(id=0,off=0,r=62) R7=imm22; r7 += r6 */ 1271 tmp_reg = *dst_reg; /* save r7 state */ 1272 *dst_reg = *src_reg; /* copy pkt_ptr state r6 into r7 */ 1273 src_reg = &tmp_reg; /* pretend it's src_reg state */ 1274 /* if the checks below reject it, the copy won't matter, 1275 * since we're rejecting the whole program. If all ok, 1276 * then imm22 state will be added to r7 1277 * and r7 will be pkt(id=0,off=22,r=62) while 1278 * r6 will stay as pkt(id=0,off=0,r=62) 1279 */ 1280 } 1281 1282 if (src_reg->type == CONST_IMM) { 1283 /* pkt_ptr += reg where reg is known constant */ 1284 imm = src_reg->imm; 1285 goto add_imm; 1286 } 1287 /* disallow pkt_ptr += reg 1288 * if reg is not uknown_value with guaranteed zero upper bits 1289 * otherwise pkt_ptr may overflow and addition will become 1290 * subtraction which is not allowed 1291 */ 1292 if (src_reg->type != UNKNOWN_VALUE) { 1293 verbose("cannot add '%s' to ptr_to_packet\n", 1294 reg_type_str[src_reg->type]); 1295 return -EACCES; 1296 } 1297 if (src_reg->imm < 48) { 1298 verbose("cannot add integer value with %lld upper zero bits to ptr_to_packet\n", 1299 src_reg->imm); 1300 return -EACCES; 1301 } 1302 /* dst_reg stays as pkt_ptr type and since some positive 1303 * integer value was added to the pointer, increment its 'id' 1304 */ 1305 dst_reg->id = ++env->id_gen; 1306 1307 /* something was added to pkt_ptr, set range and off to zero */ 1308 dst_reg->off = 0; 1309 dst_reg->range = 0; 1310 } 1311 return 0; 1312 } 1313 1314 static int evaluate_reg_alu(struct verifier_env *env, struct bpf_insn *insn) 1315 { 1316 struct reg_state *regs = env->cur_state.regs; 1317 struct reg_state *dst_reg = ®s[insn->dst_reg]; 1318 u8 opcode = BPF_OP(insn->code); 1319 s64 imm_log2; 1320 1321 /* for type == UNKNOWN_VALUE: 1322 * imm > 0 -> number of zero upper bits 1323 * imm == 0 -> don't track which is the same as all bits can be non-zero 1324 */ 1325 1326 if (BPF_SRC(insn->code) == BPF_X) { 1327 struct reg_state *src_reg = ®s[insn->src_reg]; 1328 1329 if (src_reg->type == UNKNOWN_VALUE && src_reg->imm > 0 && 1330 dst_reg->imm && opcode == BPF_ADD) { 1331 /* dreg += sreg 1332 * where both have zero upper bits. Adding them 1333 * can only result making one more bit non-zero 1334 * in the larger value. 1335 * Ex. 0xffff (imm=48) + 1 (imm=63) = 0x10000 (imm=47) 1336 * 0xffff (imm=48) + 0xffff = 0x1fffe (imm=47) 1337 */ 1338 dst_reg->imm = min(dst_reg->imm, src_reg->imm); 1339 dst_reg->imm--; 1340 return 0; 1341 } 1342 if (src_reg->type == CONST_IMM && src_reg->imm > 0 && 1343 dst_reg->imm && opcode == BPF_ADD) { 1344 /* dreg += sreg 1345 * where dreg has zero upper bits and sreg is const. 1346 * Adding them can only result making one more bit 1347 * non-zero in the larger value. 1348 */ 1349 imm_log2 = __ilog2_u64((long long)src_reg->imm); 1350 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2); 1351 dst_reg->imm--; 1352 return 0; 1353 } 1354 /* all other cases non supported yet, just mark dst_reg */ 1355 dst_reg->imm = 0; 1356 return 0; 1357 } 1358 1359 /* sign extend 32-bit imm into 64-bit to make sure that 1360 * negative values occupy bit 63. Note ilog2() would have 1361 * been incorrect, since sizeof(insn->imm) == 4 1362 */ 1363 imm_log2 = __ilog2_u64((long long)insn->imm); 1364 1365 if (dst_reg->imm && opcode == BPF_LSH) { 1366 /* reg <<= imm 1367 * if reg was a result of 2 byte load, then its imm == 48 1368 * which means that upper 48 bits are zero and shifting this reg 1369 * left by 4 would mean that upper 44 bits are still zero 1370 */ 1371 dst_reg->imm -= insn->imm; 1372 } else if (dst_reg->imm && opcode == BPF_MUL) { 1373 /* reg *= imm 1374 * if multiplying by 14 subtract 4 1375 * This is conservative calculation of upper zero bits. 1376 * It's not trying to special case insn->imm == 1 or 0 cases 1377 */ 1378 dst_reg->imm -= imm_log2 + 1; 1379 } else if (opcode == BPF_AND) { 1380 /* reg &= imm */ 1381 dst_reg->imm = 63 - imm_log2; 1382 } else if (dst_reg->imm && opcode == BPF_ADD) { 1383 /* reg += imm */ 1384 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2); 1385 dst_reg->imm--; 1386 } else if (opcode == BPF_RSH) { 1387 /* reg >>= imm 1388 * which means that after right shift, upper bits will be zero 1389 * note that verifier already checked that 1390 * 0 <= imm < 64 for shift insn 1391 */ 1392 dst_reg->imm += insn->imm; 1393 if (unlikely(dst_reg->imm > 64)) 1394 /* some dumb code did: 1395 * r2 = *(u32 *)mem; 1396 * r2 >>= 32; 1397 * and all bits are zero now */ 1398 dst_reg->imm = 64; 1399 } else { 1400 /* all other alu ops, means that we don't know what will 1401 * happen to the value, mark it with unknown number of zero bits 1402 */ 1403 dst_reg->imm = 0; 1404 } 1405 1406 if (dst_reg->imm < 0) { 1407 /* all 64 bits of the register can contain non-zero bits 1408 * and such value cannot be added to ptr_to_packet, since it 1409 * may overflow, mark it as unknown to avoid further eval 1410 */ 1411 dst_reg->imm = 0; 1412 } 1413 return 0; 1414 } 1415 1416 static int evaluate_reg_imm_alu(struct verifier_env *env, struct bpf_insn *insn) 1417 { 1418 struct reg_state *regs = env->cur_state.regs; 1419 struct reg_state *dst_reg = ®s[insn->dst_reg]; 1420 struct reg_state *src_reg = ®s[insn->src_reg]; 1421 u8 opcode = BPF_OP(insn->code); 1422 1423 /* dst_reg->type == CONST_IMM here, simulate execution of 'add' insn. 1424 * Don't care about overflow or negative values, just add them 1425 */ 1426 if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_K) 1427 dst_reg->imm += insn->imm; 1428 else if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_X && 1429 src_reg->type == CONST_IMM) 1430 dst_reg->imm += src_reg->imm; 1431 else 1432 mark_reg_unknown_value(regs, insn->dst_reg); 1433 return 0; 1434 } 1435 1436 /* check validity of 32-bit and 64-bit arithmetic operations */ 1437 static int check_alu_op(struct verifier_env *env, struct bpf_insn *insn) 1438 { 1439 struct reg_state *regs = env->cur_state.regs, *dst_reg; 1440 u8 opcode = BPF_OP(insn->code); 1441 int err; 1442 1443 if (opcode == BPF_END || opcode == BPF_NEG) { 1444 if (opcode == BPF_NEG) { 1445 if (BPF_SRC(insn->code) != 0 || 1446 insn->src_reg != BPF_REG_0 || 1447 insn->off != 0 || insn->imm != 0) { 1448 verbose("BPF_NEG uses reserved fields\n"); 1449 return -EINVAL; 1450 } 1451 } else { 1452 if (insn->src_reg != BPF_REG_0 || insn->off != 0 || 1453 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) { 1454 verbose("BPF_END uses reserved fields\n"); 1455 return -EINVAL; 1456 } 1457 } 1458 1459 /* check src operand */ 1460 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1461 if (err) 1462 return err; 1463 1464 if (is_pointer_value(env, insn->dst_reg)) { 1465 verbose("R%d pointer arithmetic prohibited\n", 1466 insn->dst_reg); 1467 return -EACCES; 1468 } 1469 1470 /* check dest operand */ 1471 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1472 if (err) 1473 return err; 1474 1475 } else if (opcode == BPF_MOV) { 1476 1477 if (BPF_SRC(insn->code) == BPF_X) { 1478 if (insn->imm != 0 || insn->off != 0) { 1479 verbose("BPF_MOV uses reserved fields\n"); 1480 return -EINVAL; 1481 } 1482 1483 /* check src operand */ 1484 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1485 if (err) 1486 return err; 1487 } else { 1488 if (insn->src_reg != BPF_REG_0 || insn->off != 0) { 1489 verbose("BPF_MOV uses reserved fields\n"); 1490 return -EINVAL; 1491 } 1492 } 1493 1494 /* check dest operand */ 1495 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1496 if (err) 1497 return err; 1498 1499 if (BPF_SRC(insn->code) == BPF_X) { 1500 if (BPF_CLASS(insn->code) == BPF_ALU64) { 1501 /* case: R1 = R2 1502 * copy register state to dest reg 1503 */ 1504 regs[insn->dst_reg] = regs[insn->src_reg]; 1505 } else { 1506 if (is_pointer_value(env, insn->src_reg)) { 1507 verbose("R%d partial copy of pointer\n", 1508 insn->src_reg); 1509 return -EACCES; 1510 } 1511 regs[insn->dst_reg].type = UNKNOWN_VALUE; 1512 regs[insn->dst_reg].map_ptr = NULL; 1513 } 1514 } else { 1515 /* case: R = imm 1516 * remember the value we stored into this reg 1517 */ 1518 regs[insn->dst_reg].type = CONST_IMM; 1519 regs[insn->dst_reg].imm = insn->imm; 1520 } 1521 1522 } else if (opcode > BPF_END) { 1523 verbose("invalid BPF_ALU opcode %x\n", opcode); 1524 return -EINVAL; 1525 1526 } else { /* all other ALU ops: and, sub, xor, add, ... */ 1527 1528 if (BPF_SRC(insn->code) == BPF_X) { 1529 if (insn->imm != 0 || insn->off != 0) { 1530 verbose("BPF_ALU uses reserved fields\n"); 1531 return -EINVAL; 1532 } 1533 /* check src1 operand */ 1534 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1535 if (err) 1536 return err; 1537 } else { 1538 if (insn->src_reg != BPF_REG_0 || insn->off != 0) { 1539 verbose("BPF_ALU uses reserved fields\n"); 1540 return -EINVAL; 1541 } 1542 } 1543 1544 /* check src2 operand */ 1545 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1546 if (err) 1547 return err; 1548 1549 if ((opcode == BPF_MOD || opcode == BPF_DIV) && 1550 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) { 1551 verbose("div by zero\n"); 1552 return -EINVAL; 1553 } 1554 1555 if ((opcode == BPF_LSH || opcode == BPF_RSH || 1556 opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) { 1557 int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32; 1558 1559 if (insn->imm < 0 || insn->imm >= size) { 1560 verbose("invalid shift %d\n", insn->imm); 1561 return -EINVAL; 1562 } 1563 } 1564 1565 /* check dest operand */ 1566 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); 1567 if (err) 1568 return err; 1569 1570 dst_reg = ®s[insn->dst_reg]; 1571 1572 /* pattern match 'bpf_add Rx, imm' instruction */ 1573 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 && 1574 dst_reg->type == FRAME_PTR && BPF_SRC(insn->code) == BPF_K) { 1575 dst_reg->type = PTR_TO_STACK; 1576 dst_reg->imm = insn->imm; 1577 return 0; 1578 } else if (opcode == BPF_ADD && 1579 BPF_CLASS(insn->code) == BPF_ALU64 && 1580 (dst_reg->type == PTR_TO_PACKET || 1581 (BPF_SRC(insn->code) == BPF_X && 1582 regs[insn->src_reg].type == PTR_TO_PACKET))) { 1583 /* ptr_to_packet += K|X */ 1584 return check_packet_ptr_add(env, insn); 1585 } else if (BPF_CLASS(insn->code) == BPF_ALU64 && 1586 dst_reg->type == UNKNOWN_VALUE && 1587 env->allow_ptr_leaks) { 1588 /* unknown += K|X */ 1589 return evaluate_reg_alu(env, insn); 1590 } else if (BPF_CLASS(insn->code) == BPF_ALU64 && 1591 dst_reg->type == CONST_IMM && 1592 env->allow_ptr_leaks) { 1593 /* reg_imm += K|X */ 1594 return evaluate_reg_imm_alu(env, insn); 1595 } else if (is_pointer_value(env, insn->dst_reg)) { 1596 verbose("R%d pointer arithmetic prohibited\n", 1597 insn->dst_reg); 1598 return -EACCES; 1599 } else if (BPF_SRC(insn->code) == BPF_X && 1600 is_pointer_value(env, insn->src_reg)) { 1601 verbose("R%d pointer arithmetic prohibited\n", 1602 insn->src_reg); 1603 return -EACCES; 1604 } 1605 1606 /* mark dest operand */ 1607 mark_reg_unknown_value(regs, insn->dst_reg); 1608 } 1609 1610 return 0; 1611 } 1612 1613 static void find_good_pkt_pointers(struct verifier_env *env, 1614 struct reg_state *dst_reg) 1615 { 1616 struct verifier_state *state = &env->cur_state; 1617 struct reg_state *regs = state->regs, *reg; 1618 int i; 1619 /* r2 = r3; 1620 * r2 += 8 1621 * if (r2 > pkt_end) goto somewhere 1622 * r2 == dst_reg, pkt_end == src_reg, 1623 * r2=pkt(id=n,off=8,r=0) 1624 * r3=pkt(id=n,off=0,r=0) 1625 * find register r3 and mark its range as r3=pkt(id=n,off=0,r=8) 1626 * so that range of bytes [r3, r3 + 8) is safe to access 1627 */ 1628 for (i = 0; i < MAX_BPF_REG; i++) 1629 if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id) 1630 regs[i].range = dst_reg->off; 1631 1632 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 1633 if (state->stack_slot_type[i] != STACK_SPILL) 1634 continue; 1635 reg = &state->spilled_regs[i / BPF_REG_SIZE]; 1636 if (reg->type == PTR_TO_PACKET && reg->id == dst_reg->id) 1637 reg->range = dst_reg->off; 1638 } 1639 } 1640 1641 static int check_cond_jmp_op(struct verifier_env *env, 1642 struct bpf_insn *insn, int *insn_idx) 1643 { 1644 struct reg_state *regs = env->cur_state.regs, *dst_reg; 1645 struct verifier_state *other_branch; 1646 u8 opcode = BPF_OP(insn->code); 1647 int err; 1648 1649 if (opcode > BPF_EXIT) { 1650 verbose("invalid BPF_JMP opcode %x\n", opcode); 1651 return -EINVAL; 1652 } 1653 1654 if (BPF_SRC(insn->code) == BPF_X) { 1655 if (insn->imm != 0) { 1656 verbose("BPF_JMP uses reserved fields\n"); 1657 return -EINVAL; 1658 } 1659 1660 /* check src1 operand */ 1661 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1662 if (err) 1663 return err; 1664 1665 if (is_pointer_value(env, insn->src_reg)) { 1666 verbose("R%d pointer comparison prohibited\n", 1667 insn->src_reg); 1668 return -EACCES; 1669 } 1670 } else { 1671 if (insn->src_reg != BPF_REG_0) { 1672 verbose("BPF_JMP uses reserved fields\n"); 1673 return -EINVAL; 1674 } 1675 } 1676 1677 /* check src2 operand */ 1678 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1679 if (err) 1680 return err; 1681 1682 dst_reg = ®s[insn->dst_reg]; 1683 1684 /* detect if R == 0 where R was initialized to zero earlier */ 1685 if (BPF_SRC(insn->code) == BPF_K && 1686 (opcode == BPF_JEQ || opcode == BPF_JNE) && 1687 dst_reg->type == CONST_IMM && dst_reg->imm == insn->imm) { 1688 if (opcode == BPF_JEQ) { 1689 /* if (imm == imm) goto pc+off; 1690 * only follow the goto, ignore fall-through 1691 */ 1692 *insn_idx += insn->off; 1693 return 0; 1694 } else { 1695 /* if (imm != imm) goto pc+off; 1696 * only follow fall-through branch, since 1697 * that's where the program will go 1698 */ 1699 return 0; 1700 } 1701 } 1702 1703 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx); 1704 if (!other_branch) 1705 return -EFAULT; 1706 1707 /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */ 1708 if (BPF_SRC(insn->code) == BPF_K && 1709 insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) && 1710 dst_reg->type == PTR_TO_MAP_VALUE_OR_NULL) { 1711 if (opcode == BPF_JEQ) { 1712 /* next fallthrough insn can access memory via 1713 * this register 1714 */ 1715 regs[insn->dst_reg].type = PTR_TO_MAP_VALUE; 1716 /* branch targer cannot access it, since reg == 0 */ 1717 mark_reg_unknown_value(other_branch->regs, 1718 insn->dst_reg); 1719 } else { 1720 other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE; 1721 mark_reg_unknown_value(regs, insn->dst_reg); 1722 } 1723 } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT && 1724 dst_reg->type == PTR_TO_PACKET && 1725 regs[insn->src_reg].type == PTR_TO_PACKET_END) { 1726 find_good_pkt_pointers(env, dst_reg); 1727 } else if (is_pointer_value(env, insn->dst_reg)) { 1728 verbose("R%d pointer comparison prohibited\n", insn->dst_reg); 1729 return -EACCES; 1730 } 1731 if (log_level) 1732 print_verifier_state(&env->cur_state); 1733 return 0; 1734 } 1735 1736 /* return the map pointer stored inside BPF_LD_IMM64 instruction */ 1737 static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn) 1738 { 1739 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32; 1740 1741 return (struct bpf_map *) (unsigned long) imm64; 1742 } 1743 1744 /* verify BPF_LD_IMM64 instruction */ 1745 static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn) 1746 { 1747 struct reg_state *regs = env->cur_state.regs; 1748 int err; 1749 1750 if (BPF_SIZE(insn->code) != BPF_DW) { 1751 verbose("invalid BPF_LD_IMM insn\n"); 1752 return -EINVAL; 1753 } 1754 if (insn->off != 0) { 1755 verbose("BPF_LD_IMM64 uses reserved fields\n"); 1756 return -EINVAL; 1757 } 1758 1759 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1760 if (err) 1761 return err; 1762 1763 if (insn->src_reg == 0) 1764 /* generic move 64-bit immediate into a register */ 1765 return 0; 1766 1767 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */ 1768 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD); 1769 1770 regs[insn->dst_reg].type = CONST_PTR_TO_MAP; 1771 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn); 1772 return 0; 1773 } 1774 1775 static bool may_access_skb(enum bpf_prog_type type) 1776 { 1777 switch (type) { 1778 case BPF_PROG_TYPE_SOCKET_FILTER: 1779 case BPF_PROG_TYPE_SCHED_CLS: 1780 case BPF_PROG_TYPE_SCHED_ACT: 1781 return true; 1782 default: 1783 return false; 1784 } 1785 } 1786 1787 /* verify safety of LD_ABS|LD_IND instructions: 1788 * - they can only appear in the programs where ctx == skb 1789 * - since they are wrappers of function calls, they scratch R1-R5 registers, 1790 * preserve R6-R9, and store return value into R0 1791 * 1792 * Implicit input: 1793 * ctx == skb == R6 == CTX 1794 * 1795 * Explicit input: 1796 * SRC == any register 1797 * IMM == 32-bit immediate 1798 * 1799 * Output: 1800 * R0 - 8/16/32-bit skb data converted to cpu endianness 1801 */ 1802 static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn) 1803 { 1804 struct reg_state *regs = env->cur_state.regs; 1805 u8 mode = BPF_MODE(insn->code); 1806 struct reg_state *reg; 1807 int i, err; 1808 1809 if (!may_access_skb(env->prog->type)) { 1810 verbose("BPF_LD_[ABS|IND] instructions not allowed for this program type\n"); 1811 return -EINVAL; 1812 } 1813 1814 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 || 1815 BPF_SIZE(insn->code) == BPF_DW || 1816 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) { 1817 verbose("BPF_LD_[ABS|IND] uses reserved fields\n"); 1818 return -EINVAL; 1819 } 1820 1821 /* check whether implicit source operand (register R6) is readable */ 1822 err = check_reg_arg(regs, BPF_REG_6, SRC_OP); 1823 if (err) 1824 return err; 1825 1826 if (regs[BPF_REG_6].type != PTR_TO_CTX) { 1827 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n"); 1828 return -EINVAL; 1829 } 1830 1831 if (mode == BPF_IND) { 1832 /* check explicit source operand */ 1833 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1834 if (err) 1835 return err; 1836 } 1837 1838 /* reset caller saved regs to unreadable */ 1839 for (i = 0; i < CALLER_SAVED_REGS; i++) { 1840 reg = regs + caller_saved[i]; 1841 reg->type = NOT_INIT; 1842 reg->imm = 0; 1843 } 1844 1845 /* mark destination R0 register as readable, since it contains 1846 * the value fetched from the packet 1847 */ 1848 regs[BPF_REG_0].type = UNKNOWN_VALUE; 1849 return 0; 1850 } 1851 1852 /* non-recursive DFS pseudo code 1853 * 1 procedure DFS-iterative(G,v): 1854 * 2 label v as discovered 1855 * 3 let S be a stack 1856 * 4 S.push(v) 1857 * 5 while S is not empty 1858 * 6 t <- S.pop() 1859 * 7 if t is what we're looking for: 1860 * 8 return t 1861 * 9 for all edges e in G.adjacentEdges(t) do 1862 * 10 if edge e is already labelled 1863 * 11 continue with the next edge 1864 * 12 w <- G.adjacentVertex(t,e) 1865 * 13 if vertex w is not discovered and not explored 1866 * 14 label e as tree-edge 1867 * 15 label w as discovered 1868 * 16 S.push(w) 1869 * 17 continue at 5 1870 * 18 else if vertex w is discovered 1871 * 19 label e as back-edge 1872 * 20 else 1873 * 21 // vertex w is explored 1874 * 22 label e as forward- or cross-edge 1875 * 23 label t as explored 1876 * 24 S.pop() 1877 * 1878 * convention: 1879 * 0x10 - discovered 1880 * 0x11 - discovered and fall-through edge labelled 1881 * 0x12 - discovered and fall-through and branch edges labelled 1882 * 0x20 - explored 1883 */ 1884 1885 enum { 1886 DISCOVERED = 0x10, 1887 EXPLORED = 0x20, 1888 FALLTHROUGH = 1, 1889 BRANCH = 2, 1890 }; 1891 1892 #define STATE_LIST_MARK ((struct verifier_state_list *) -1L) 1893 1894 static int *insn_stack; /* stack of insns to process */ 1895 static int cur_stack; /* current stack index */ 1896 static int *insn_state; 1897 1898 /* t, w, e - match pseudo-code above: 1899 * t - index of current instruction 1900 * w - next instruction 1901 * e - edge 1902 */ 1903 static int push_insn(int t, int w, int e, struct verifier_env *env) 1904 { 1905 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH)) 1906 return 0; 1907 1908 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH)) 1909 return 0; 1910 1911 if (w < 0 || w >= env->prog->len) { 1912 verbose("jump out of range from insn %d to %d\n", t, w); 1913 return -EINVAL; 1914 } 1915 1916 if (e == BRANCH) 1917 /* mark branch target for state pruning */ 1918 env->explored_states[w] = STATE_LIST_MARK; 1919 1920 if (insn_state[w] == 0) { 1921 /* tree-edge */ 1922 insn_state[t] = DISCOVERED | e; 1923 insn_state[w] = DISCOVERED; 1924 if (cur_stack >= env->prog->len) 1925 return -E2BIG; 1926 insn_stack[cur_stack++] = w; 1927 return 1; 1928 } else if ((insn_state[w] & 0xF0) == DISCOVERED) { 1929 verbose("back-edge from insn %d to %d\n", t, w); 1930 return -EINVAL; 1931 } else if (insn_state[w] == EXPLORED) { 1932 /* forward- or cross-edge */ 1933 insn_state[t] = DISCOVERED | e; 1934 } else { 1935 verbose("insn state internal bug\n"); 1936 return -EFAULT; 1937 } 1938 return 0; 1939 } 1940 1941 /* non-recursive depth-first-search to detect loops in BPF program 1942 * loop == back-edge in directed graph 1943 */ 1944 static int check_cfg(struct verifier_env *env) 1945 { 1946 struct bpf_insn *insns = env->prog->insnsi; 1947 int insn_cnt = env->prog->len; 1948 int ret = 0; 1949 int i, t; 1950 1951 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 1952 if (!insn_state) 1953 return -ENOMEM; 1954 1955 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 1956 if (!insn_stack) { 1957 kfree(insn_state); 1958 return -ENOMEM; 1959 } 1960 1961 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */ 1962 insn_stack[0] = 0; /* 0 is the first instruction */ 1963 cur_stack = 1; 1964 1965 peek_stack: 1966 if (cur_stack == 0) 1967 goto check_state; 1968 t = insn_stack[cur_stack - 1]; 1969 1970 if (BPF_CLASS(insns[t].code) == BPF_JMP) { 1971 u8 opcode = BPF_OP(insns[t].code); 1972 1973 if (opcode == BPF_EXIT) { 1974 goto mark_explored; 1975 } else if (opcode == BPF_CALL) { 1976 ret = push_insn(t, t + 1, FALLTHROUGH, env); 1977 if (ret == 1) 1978 goto peek_stack; 1979 else if (ret < 0) 1980 goto err_free; 1981 if (t + 1 < insn_cnt) 1982 env->explored_states[t + 1] = STATE_LIST_MARK; 1983 } else if (opcode == BPF_JA) { 1984 if (BPF_SRC(insns[t].code) != BPF_K) { 1985 ret = -EINVAL; 1986 goto err_free; 1987 } 1988 /* unconditional jump with single edge */ 1989 ret = push_insn(t, t + insns[t].off + 1, 1990 FALLTHROUGH, env); 1991 if (ret == 1) 1992 goto peek_stack; 1993 else if (ret < 0) 1994 goto err_free; 1995 /* tell verifier to check for equivalent states 1996 * after every call and jump 1997 */ 1998 if (t + 1 < insn_cnt) 1999 env->explored_states[t + 1] = STATE_LIST_MARK; 2000 } else { 2001 /* conditional jump with two edges */ 2002 ret = push_insn(t, t + 1, FALLTHROUGH, env); 2003 if (ret == 1) 2004 goto peek_stack; 2005 else if (ret < 0) 2006 goto err_free; 2007 2008 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env); 2009 if (ret == 1) 2010 goto peek_stack; 2011 else if (ret < 0) 2012 goto err_free; 2013 } 2014 } else { 2015 /* all other non-branch instructions with single 2016 * fall-through edge 2017 */ 2018 ret = push_insn(t, t + 1, FALLTHROUGH, env); 2019 if (ret == 1) 2020 goto peek_stack; 2021 else if (ret < 0) 2022 goto err_free; 2023 } 2024 2025 mark_explored: 2026 insn_state[t] = EXPLORED; 2027 if (cur_stack-- <= 0) { 2028 verbose("pop stack internal bug\n"); 2029 ret = -EFAULT; 2030 goto err_free; 2031 } 2032 goto peek_stack; 2033 2034 check_state: 2035 for (i = 0; i < insn_cnt; i++) { 2036 if (insn_state[i] != EXPLORED) { 2037 verbose("unreachable insn %d\n", i); 2038 ret = -EINVAL; 2039 goto err_free; 2040 } 2041 } 2042 ret = 0; /* cfg looks good */ 2043 2044 err_free: 2045 kfree(insn_state); 2046 kfree(insn_stack); 2047 return ret; 2048 } 2049 2050 /* the following conditions reduce the number of explored insns 2051 * from ~140k to ~80k for ultra large programs that use a lot of ptr_to_packet 2052 */ 2053 static bool compare_ptrs_to_packet(struct reg_state *old, struct reg_state *cur) 2054 { 2055 if (old->id != cur->id) 2056 return false; 2057 2058 /* old ptr_to_packet is more conservative, since it allows smaller 2059 * range. Ex: 2060 * old(off=0,r=10) is equal to cur(off=0,r=20), because 2061 * old(off=0,r=10) means that with range=10 the verifier proceeded 2062 * further and found no issues with the program. Now we're in the same 2063 * spot with cur(off=0,r=20), so we're safe too, since anything further 2064 * will only be looking at most 10 bytes after this pointer. 2065 */ 2066 if (old->off == cur->off && old->range < cur->range) 2067 return true; 2068 2069 /* old(off=20,r=10) is equal to cur(off=22,re=22 or 5 or 0) 2070 * since both cannot be used for packet access and safe(old) 2071 * pointer has smaller off that could be used for further 2072 * 'if (ptr > data_end)' check 2073 * Ex: 2074 * old(off=20,r=10) and cur(off=22,r=22) and cur(off=22,r=0) mean 2075 * that we cannot access the packet. 2076 * The safe range is: 2077 * [ptr, ptr + range - off) 2078 * so whenever off >=range, it means no safe bytes from this pointer. 2079 * When comparing old->off <= cur->off, it means that older code 2080 * went with smaller offset and that offset was later 2081 * used to figure out the safe range after 'if (ptr > data_end)' check 2082 * Say, 'old' state was explored like: 2083 * ... R3(off=0, r=0) 2084 * R4 = R3 + 20 2085 * ... now R4(off=20,r=0) <-- here 2086 * if (R4 > data_end) 2087 * ... R4(off=20,r=20), R3(off=0,r=20) and R3 can be used to access. 2088 * ... the code further went all the way to bpf_exit. 2089 * Now the 'cur' state at the mark 'here' has R4(off=30,r=0). 2090 * old_R4(off=20,r=0) equal to cur_R4(off=30,r=0), since if the verifier 2091 * goes further, such cur_R4 will give larger safe packet range after 2092 * 'if (R4 > data_end)' and all further insn were already good with r=20, 2093 * so they will be good with r=30 and we can prune the search. 2094 */ 2095 if (old->off <= cur->off && 2096 old->off >= old->range && cur->off >= cur->range) 2097 return true; 2098 2099 return false; 2100 } 2101 2102 /* compare two verifier states 2103 * 2104 * all states stored in state_list are known to be valid, since 2105 * verifier reached 'bpf_exit' instruction through them 2106 * 2107 * this function is called when verifier exploring different branches of 2108 * execution popped from the state stack. If it sees an old state that has 2109 * more strict register state and more strict stack state then this execution 2110 * branch doesn't need to be explored further, since verifier already 2111 * concluded that more strict state leads to valid finish. 2112 * 2113 * Therefore two states are equivalent if register state is more conservative 2114 * and explored stack state is more conservative than the current one. 2115 * Example: 2116 * explored current 2117 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC) 2118 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC) 2119 * 2120 * In other words if current stack state (one being explored) has more 2121 * valid slots than old one that already passed validation, it means 2122 * the verifier can stop exploring and conclude that current state is valid too 2123 * 2124 * Similarly with registers. If explored state has register type as invalid 2125 * whereas register type in current state is meaningful, it means that 2126 * the current state will reach 'bpf_exit' instruction safely 2127 */ 2128 static bool states_equal(struct verifier_state *old, struct verifier_state *cur) 2129 { 2130 struct reg_state *rold, *rcur; 2131 int i; 2132 2133 for (i = 0; i < MAX_BPF_REG; i++) { 2134 rold = &old->regs[i]; 2135 rcur = &cur->regs[i]; 2136 2137 if (memcmp(rold, rcur, sizeof(*rold)) == 0) 2138 continue; 2139 2140 if (rold->type == NOT_INIT || 2141 (rold->type == UNKNOWN_VALUE && rcur->type != NOT_INIT)) 2142 continue; 2143 2144 if (rold->type == PTR_TO_PACKET && rcur->type == PTR_TO_PACKET && 2145 compare_ptrs_to_packet(rold, rcur)) 2146 continue; 2147 2148 return false; 2149 } 2150 2151 for (i = 0; i < MAX_BPF_STACK; i++) { 2152 if (old->stack_slot_type[i] == STACK_INVALID) 2153 continue; 2154 if (old->stack_slot_type[i] != cur->stack_slot_type[i]) 2155 /* Ex: old explored (safe) state has STACK_SPILL in 2156 * this stack slot, but current has has STACK_MISC -> 2157 * this verifier states are not equivalent, 2158 * return false to continue verification of this path 2159 */ 2160 return false; 2161 if (i % BPF_REG_SIZE) 2162 continue; 2163 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE], 2164 &cur->spilled_regs[i / BPF_REG_SIZE], 2165 sizeof(old->spilled_regs[0]))) 2166 /* when explored and current stack slot types are 2167 * the same, check that stored pointers types 2168 * are the same as well. 2169 * Ex: explored safe path could have stored 2170 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8} 2171 * but current path has stored: 2172 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16} 2173 * such verifier states are not equivalent. 2174 * return false to continue verification of this path 2175 */ 2176 return false; 2177 else 2178 continue; 2179 } 2180 return true; 2181 } 2182 2183 static int is_state_visited(struct verifier_env *env, int insn_idx) 2184 { 2185 struct verifier_state_list *new_sl; 2186 struct verifier_state_list *sl; 2187 2188 sl = env->explored_states[insn_idx]; 2189 if (!sl) 2190 /* this 'insn_idx' instruction wasn't marked, so we will not 2191 * be doing state search here 2192 */ 2193 return 0; 2194 2195 while (sl != STATE_LIST_MARK) { 2196 if (states_equal(&sl->state, &env->cur_state)) 2197 /* reached equivalent register/stack state, 2198 * prune the search 2199 */ 2200 return 1; 2201 sl = sl->next; 2202 } 2203 2204 /* there were no equivalent states, remember current one. 2205 * technically the current state is not proven to be safe yet, 2206 * but it will either reach bpf_exit (which means it's safe) or 2207 * it will be rejected. Since there are no loops, we won't be 2208 * seeing this 'insn_idx' instruction again on the way to bpf_exit 2209 */ 2210 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER); 2211 if (!new_sl) 2212 return -ENOMEM; 2213 2214 /* add new state to the head of linked list */ 2215 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state)); 2216 new_sl->next = env->explored_states[insn_idx]; 2217 env->explored_states[insn_idx] = new_sl; 2218 return 0; 2219 } 2220 2221 static int do_check(struct verifier_env *env) 2222 { 2223 struct verifier_state *state = &env->cur_state; 2224 struct bpf_insn *insns = env->prog->insnsi; 2225 struct reg_state *regs = state->regs; 2226 int insn_cnt = env->prog->len; 2227 int insn_idx, prev_insn_idx = 0; 2228 int insn_processed = 0; 2229 bool do_print_state = false; 2230 2231 init_reg_state(regs); 2232 insn_idx = 0; 2233 for (;;) { 2234 struct bpf_insn *insn; 2235 u8 class; 2236 int err; 2237 2238 if (insn_idx >= insn_cnt) { 2239 verbose("invalid insn idx %d insn_cnt %d\n", 2240 insn_idx, insn_cnt); 2241 return -EFAULT; 2242 } 2243 2244 insn = &insns[insn_idx]; 2245 class = BPF_CLASS(insn->code); 2246 2247 if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) { 2248 verbose("BPF program is too large. Proccessed %d insn\n", 2249 insn_processed); 2250 return -E2BIG; 2251 } 2252 2253 err = is_state_visited(env, insn_idx); 2254 if (err < 0) 2255 return err; 2256 if (err == 1) { 2257 /* found equivalent state, can prune the search */ 2258 if (log_level) { 2259 if (do_print_state) 2260 verbose("\nfrom %d to %d: safe\n", 2261 prev_insn_idx, insn_idx); 2262 else 2263 verbose("%d: safe\n", insn_idx); 2264 } 2265 goto process_bpf_exit; 2266 } 2267 2268 if (log_level && do_print_state) { 2269 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx); 2270 print_verifier_state(&env->cur_state); 2271 do_print_state = false; 2272 } 2273 2274 if (log_level) { 2275 verbose("%d: ", insn_idx); 2276 print_bpf_insn(insn); 2277 } 2278 2279 if (class == BPF_ALU || class == BPF_ALU64) { 2280 err = check_alu_op(env, insn); 2281 if (err) 2282 return err; 2283 2284 } else if (class == BPF_LDX) { 2285 enum bpf_reg_type src_reg_type; 2286 2287 /* check for reserved fields is already done */ 2288 2289 /* check src operand */ 2290 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2291 if (err) 2292 return err; 2293 2294 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); 2295 if (err) 2296 return err; 2297 2298 src_reg_type = regs[insn->src_reg].type; 2299 2300 /* check that memory (src_reg + off) is readable, 2301 * the state of dst_reg will be updated by this func 2302 */ 2303 err = check_mem_access(env, insn->src_reg, insn->off, 2304 BPF_SIZE(insn->code), BPF_READ, 2305 insn->dst_reg); 2306 if (err) 2307 return err; 2308 2309 if (BPF_SIZE(insn->code) != BPF_W) { 2310 insn_idx++; 2311 continue; 2312 } 2313 2314 if (insn->imm == 0) { 2315 /* saw a valid insn 2316 * dst_reg = *(u32 *)(src_reg + off) 2317 * use reserved 'imm' field to mark this insn 2318 */ 2319 insn->imm = src_reg_type; 2320 2321 } else if (src_reg_type != insn->imm && 2322 (src_reg_type == PTR_TO_CTX || 2323 insn->imm == PTR_TO_CTX)) { 2324 /* ABuser program is trying to use the same insn 2325 * dst_reg = *(u32*) (src_reg + off) 2326 * with different pointer types: 2327 * src_reg == ctx in one branch and 2328 * src_reg == stack|map in some other branch. 2329 * Reject it. 2330 */ 2331 verbose("same insn cannot be used with different pointers\n"); 2332 return -EINVAL; 2333 } 2334 2335 } else if (class == BPF_STX) { 2336 enum bpf_reg_type dst_reg_type; 2337 2338 if (BPF_MODE(insn->code) == BPF_XADD) { 2339 err = check_xadd(env, insn); 2340 if (err) 2341 return err; 2342 insn_idx++; 2343 continue; 2344 } 2345 2346 /* check src1 operand */ 2347 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2348 if (err) 2349 return err; 2350 /* check src2 operand */ 2351 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 2352 if (err) 2353 return err; 2354 2355 dst_reg_type = regs[insn->dst_reg].type; 2356 2357 /* check that memory (dst_reg + off) is writeable */ 2358 err = check_mem_access(env, insn->dst_reg, insn->off, 2359 BPF_SIZE(insn->code), BPF_WRITE, 2360 insn->src_reg); 2361 if (err) 2362 return err; 2363 2364 if (insn->imm == 0) { 2365 insn->imm = dst_reg_type; 2366 } else if (dst_reg_type != insn->imm && 2367 (dst_reg_type == PTR_TO_CTX || 2368 insn->imm == PTR_TO_CTX)) { 2369 verbose("same insn cannot be used with different pointers\n"); 2370 return -EINVAL; 2371 } 2372 2373 } else if (class == BPF_ST) { 2374 if (BPF_MODE(insn->code) != BPF_MEM || 2375 insn->src_reg != BPF_REG_0) { 2376 verbose("BPF_ST uses reserved fields\n"); 2377 return -EINVAL; 2378 } 2379 /* check src operand */ 2380 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 2381 if (err) 2382 return err; 2383 2384 /* check that memory (dst_reg + off) is writeable */ 2385 err = check_mem_access(env, insn->dst_reg, insn->off, 2386 BPF_SIZE(insn->code), BPF_WRITE, 2387 -1); 2388 if (err) 2389 return err; 2390 2391 } else if (class == BPF_JMP) { 2392 u8 opcode = BPF_OP(insn->code); 2393 2394 if (opcode == BPF_CALL) { 2395 if (BPF_SRC(insn->code) != BPF_K || 2396 insn->off != 0 || 2397 insn->src_reg != BPF_REG_0 || 2398 insn->dst_reg != BPF_REG_0) { 2399 verbose("BPF_CALL uses reserved fields\n"); 2400 return -EINVAL; 2401 } 2402 2403 err = check_call(env, insn->imm); 2404 if (err) 2405 return err; 2406 2407 } else if (opcode == BPF_JA) { 2408 if (BPF_SRC(insn->code) != BPF_K || 2409 insn->imm != 0 || 2410 insn->src_reg != BPF_REG_0 || 2411 insn->dst_reg != BPF_REG_0) { 2412 verbose("BPF_JA uses reserved fields\n"); 2413 return -EINVAL; 2414 } 2415 2416 insn_idx += insn->off + 1; 2417 continue; 2418 2419 } else if (opcode == BPF_EXIT) { 2420 if (BPF_SRC(insn->code) != BPF_K || 2421 insn->imm != 0 || 2422 insn->src_reg != BPF_REG_0 || 2423 insn->dst_reg != BPF_REG_0) { 2424 verbose("BPF_EXIT uses reserved fields\n"); 2425 return -EINVAL; 2426 } 2427 2428 /* eBPF calling convetion is such that R0 is used 2429 * to return the value from eBPF program. 2430 * Make sure that it's readable at this time 2431 * of bpf_exit, which means that program wrote 2432 * something into it earlier 2433 */ 2434 err = check_reg_arg(regs, BPF_REG_0, SRC_OP); 2435 if (err) 2436 return err; 2437 2438 if (is_pointer_value(env, BPF_REG_0)) { 2439 verbose("R0 leaks addr as return value\n"); 2440 return -EACCES; 2441 } 2442 2443 process_bpf_exit: 2444 insn_idx = pop_stack(env, &prev_insn_idx); 2445 if (insn_idx < 0) { 2446 break; 2447 } else { 2448 do_print_state = true; 2449 continue; 2450 } 2451 } else { 2452 err = check_cond_jmp_op(env, insn, &insn_idx); 2453 if (err) 2454 return err; 2455 } 2456 } else if (class == BPF_LD) { 2457 u8 mode = BPF_MODE(insn->code); 2458 2459 if (mode == BPF_ABS || mode == BPF_IND) { 2460 err = check_ld_abs(env, insn); 2461 if (err) 2462 return err; 2463 2464 } else if (mode == BPF_IMM) { 2465 err = check_ld_imm(env, insn); 2466 if (err) 2467 return err; 2468 2469 insn_idx++; 2470 } else { 2471 verbose("invalid BPF_LD mode\n"); 2472 return -EINVAL; 2473 } 2474 } else { 2475 verbose("unknown insn class %d\n", class); 2476 return -EINVAL; 2477 } 2478 2479 insn_idx++; 2480 } 2481 2482 verbose("processed %d insns\n", insn_processed); 2483 return 0; 2484 } 2485 2486 /* look for pseudo eBPF instructions that access map FDs and 2487 * replace them with actual map pointers 2488 */ 2489 static int replace_map_fd_with_map_ptr(struct verifier_env *env) 2490 { 2491 struct bpf_insn *insn = env->prog->insnsi; 2492 int insn_cnt = env->prog->len; 2493 int i, j; 2494 2495 for (i = 0; i < insn_cnt; i++, insn++) { 2496 if (BPF_CLASS(insn->code) == BPF_LDX && 2497 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) { 2498 verbose("BPF_LDX uses reserved fields\n"); 2499 return -EINVAL; 2500 } 2501 2502 if (BPF_CLASS(insn->code) == BPF_STX && 2503 ((BPF_MODE(insn->code) != BPF_MEM && 2504 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) { 2505 verbose("BPF_STX uses reserved fields\n"); 2506 return -EINVAL; 2507 } 2508 2509 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) { 2510 struct bpf_map *map; 2511 struct fd f; 2512 2513 if (i == insn_cnt - 1 || insn[1].code != 0 || 2514 insn[1].dst_reg != 0 || insn[1].src_reg != 0 || 2515 insn[1].off != 0) { 2516 verbose("invalid bpf_ld_imm64 insn\n"); 2517 return -EINVAL; 2518 } 2519 2520 if (insn->src_reg == 0) 2521 /* valid generic load 64-bit imm */ 2522 goto next_insn; 2523 2524 if (insn->src_reg != BPF_PSEUDO_MAP_FD) { 2525 verbose("unrecognized bpf_ld_imm64 insn\n"); 2526 return -EINVAL; 2527 } 2528 2529 f = fdget(insn->imm); 2530 map = __bpf_map_get(f); 2531 if (IS_ERR(map)) { 2532 verbose("fd %d is not pointing to valid bpf_map\n", 2533 insn->imm); 2534 return PTR_ERR(map); 2535 } 2536 2537 /* store map pointer inside BPF_LD_IMM64 instruction */ 2538 insn[0].imm = (u32) (unsigned long) map; 2539 insn[1].imm = ((u64) (unsigned long) map) >> 32; 2540 2541 /* check whether we recorded this map already */ 2542 for (j = 0; j < env->used_map_cnt; j++) 2543 if (env->used_maps[j] == map) { 2544 fdput(f); 2545 goto next_insn; 2546 } 2547 2548 if (env->used_map_cnt >= MAX_USED_MAPS) { 2549 fdput(f); 2550 return -E2BIG; 2551 } 2552 2553 /* hold the map. If the program is rejected by verifier, 2554 * the map will be released by release_maps() or it 2555 * will be used by the valid program until it's unloaded 2556 * and all maps are released in free_bpf_prog_info() 2557 */ 2558 map = bpf_map_inc(map, false); 2559 if (IS_ERR(map)) { 2560 fdput(f); 2561 return PTR_ERR(map); 2562 } 2563 env->used_maps[env->used_map_cnt++] = map; 2564 2565 fdput(f); 2566 next_insn: 2567 insn++; 2568 i++; 2569 } 2570 } 2571 2572 /* now all pseudo BPF_LD_IMM64 instructions load valid 2573 * 'struct bpf_map *' into a register instead of user map_fd. 2574 * These pointers will be used later by verifier to validate map access. 2575 */ 2576 return 0; 2577 } 2578 2579 /* drop refcnt of maps used by the rejected program */ 2580 static void release_maps(struct verifier_env *env) 2581 { 2582 int i; 2583 2584 for (i = 0; i < env->used_map_cnt; i++) 2585 bpf_map_put(env->used_maps[i]); 2586 } 2587 2588 /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */ 2589 static void convert_pseudo_ld_imm64(struct verifier_env *env) 2590 { 2591 struct bpf_insn *insn = env->prog->insnsi; 2592 int insn_cnt = env->prog->len; 2593 int i; 2594 2595 for (i = 0; i < insn_cnt; i++, insn++) 2596 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW)) 2597 insn->src_reg = 0; 2598 } 2599 2600 /* convert load instructions that access fields of 'struct __sk_buff' 2601 * into sequence of instructions that access fields of 'struct sk_buff' 2602 */ 2603 static int convert_ctx_accesses(struct verifier_env *env) 2604 { 2605 struct bpf_insn *insn = env->prog->insnsi; 2606 int insn_cnt = env->prog->len; 2607 struct bpf_insn insn_buf[16]; 2608 struct bpf_prog *new_prog; 2609 enum bpf_access_type type; 2610 int i; 2611 2612 if (!env->prog->aux->ops->convert_ctx_access) 2613 return 0; 2614 2615 for (i = 0; i < insn_cnt; i++, insn++) { 2616 u32 insn_delta, cnt; 2617 2618 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W)) 2619 type = BPF_READ; 2620 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W)) 2621 type = BPF_WRITE; 2622 else 2623 continue; 2624 2625 if (insn->imm != PTR_TO_CTX) { 2626 /* clear internal mark */ 2627 insn->imm = 0; 2628 continue; 2629 } 2630 2631 cnt = env->prog->aux->ops-> 2632 convert_ctx_access(type, insn->dst_reg, insn->src_reg, 2633 insn->off, insn_buf, env->prog); 2634 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) { 2635 verbose("bpf verifier is misconfigured\n"); 2636 return -EINVAL; 2637 } 2638 2639 new_prog = bpf_patch_insn_single(env->prog, i, insn_buf, cnt); 2640 if (!new_prog) 2641 return -ENOMEM; 2642 2643 insn_delta = cnt - 1; 2644 2645 /* keep walking new program and skip insns we just inserted */ 2646 env->prog = new_prog; 2647 insn = new_prog->insnsi + i + insn_delta; 2648 2649 insn_cnt += insn_delta; 2650 i += insn_delta; 2651 } 2652 2653 return 0; 2654 } 2655 2656 static void free_states(struct verifier_env *env) 2657 { 2658 struct verifier_state_list *sl, *sln; 2659 int i; 2660 2661 if (!env->explored_states) 2662 return; 2663 2664 for (i = 0; i < env->prog->len; i++) { 2665 sl = env->explored_states[i]; 2666 2667 if (sl) 2668 while (sl != STATE_LIST_MARK) { 2669 sln = sl->next; 2670 kfree(sl); 2671 sl = sln; 2672 } 2673 } 2674 2675 kfree(env->explored_states); 2676 } 2677 2678 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) 2679 { 2680 char __user *log_ubuf = NULL; 2681 struct verifier_env *env; 2682 int ret = -EINVAL; 2683 2684 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS) 2685 return -E2BIG; 2686 2687 /* 'struct verifier_env' can be global, but since it's not small, 2688 * allocate/free it every time bpf_check() is called 2689 */ 2690 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL); 2691 if (!env) 2692 return -ENOMEM; 2693 2694 env->prog = *prog; 2695 2696 /* grab the mutex to protect few globals used by verifier */ 2697 mutex_lock(&bpf_verifier_lock); 2698 2699 if (attr->log_level || attr->log_buf || attr->log_size) { 2700 /* user requested verbose verifier output 2701 * and supplied buffer to store the verification trace 2702 */ 2703 log_level = attr->log_level; 2704 log_ubuf = (char __user *) (unsigned long) attr->log_buf; 2705 log_size = attr->log_size; 2706 log_len = 0; 2707 2708 ret = -EINVAL; 2709 /* log_* values have to be sane */ 2710 if (log_size < 128 || log_size > UINT_MAX >> 8 || 2711 log_level == 0 || log_ubuf == NULL) 2712 goto free_env; 2713 2714 ret = -ENOMEM; 2715 log_buf = vmalloc(log_size); 2716 if (!log_buf) 2717 goto free_env; 2718 } else { 2719 log_level = 0; 2720 } 2721 2722 ret = replace_map_fd_with_map_ptr(env); 2723 if (ret < 0) 2724 goto skip_full_check; 2725 2726 env->explored_states = kcalloc(env->prog->len, 2727 sizeof(struct verifier_state_list *), 2728 GFP_USER); 2729 ret = -ENOMEM; 2730 if (!env->explored_states) 2731 goto skip_full_check; 2732 2733 ret = check_cfg(env); 2734 if (ret < 0) 2735 goto skip_full_check; 2736 2737 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); 2738 2739 ret = do_check(env); 2740 2741 skip_full_check: 2742 while (pop_stack(env, NULL) >= 0); 2743 free_states(env); 2744 2745 if (ret == 0) 2746 /* program is valid, convert *(u32*)(ctx + off) accesses */ 2747 ret = convert_ctx_accesses(env); 2748 2749 if (log_level && log_len >= log_size - 1) { 2750 BUG_ON(log_len >= log_size); 2751 /* verifier log exceeded user supplied buffer */ 2752 ret = -ENOSPC; 2753 /* fall through to return what was recorded */ 2754 } 2755 2756 /* copy verifier log back to user space including trailing zero */ 2757 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) { 2758 ret = -EFAULT; 2759 goto free_log_buf; 2760 } 2761 2762 if (ret == 0 && env->used_map_cnt) { 2763 /* if program passed verifier, update used_maps in bpf_prog_info */ 2764 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt, 2765 sizeof(env->used_maps[0]), 2766 GFP_KERNEL); 2767 2768 if (!env->prog->aux->used_maps) { 2769 ret = -ENOMEM; 2770 goto free_log_buf; 2771 } 2772 2773 memcpy(env->prog->aux->used_maps, env->used_maps, 2774 sizeof(env->used_maps[0]) * env->used_map_cnt); 2775 env->prog->aux->used_map_cnt = env->used_map_cnt; 2776 2777 /* program is valid. Convert pseudo bpf_ld_imm64 into generic 2778 * bpf_ld_imm64 instructions 2779 */ 2780 convert_pseudo_ld_imm64(env); 2781 } 2782 2783 free_log_buf: 2784 if (log_level) 2785 vfree(log_buf); 2786 free_env: 2787 if (!env->prog->aux->used_maps) 2788 /* if we didn't copy map pointers into bpf_prog_info, release 2789 * them now. Otherwise free_bpf_prog_info() will release them. 2790 */ 2791 release_maps(env); 2792 *prog = env->prog; 2793 kfree(env); 2794 mutex_unlock(&bpf_verifier_lock); 2795 return ret; 2796 } 2797