1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com 2 * 3 * This program is free software; you can redistribute it and/or 4 * modify it under the terms of version 2 of the GNU General Public 5 * License as published by the Free Software Foundation. 6 * 7 * This program is distributed in the hope that it will be useful, but 8 * WITHOUT ANY WARRANTY; without even the implied warranty of 9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 10 * General Public License for more details. 11 */ 12 #include <linux/kernel.h> 13 #include <linux/types.h> 14 #include <linux/slab.h> 15 #include <linux/bpf.h> 16 #include <linux/filter.h> 17 #include <net/netlink.h> 18 #include <linux/file.h> 19 #include <linux/vmalloc.h> 20 21 /* bpf_check() is a static code analyzer that walks eBPF program 22 * instruction by instruction and updates register/stack state. 23 * All paths of conditional branches are analyzed until 'bpf_exit' insn. 24 * 25 * The first pass is depth-first-search to check that the program is a DAG. 26 * It rejects the following programs: 27 * - larger than BPF_MAXINSNS insns 28 * - if loop is present (detected via back-edge) 29 * - unreachable insns exist (shouldn't be a forest. program = one function) 30 * - out of bounds or malformed jumps 31 * The second pass is all possible path descent from the 1st insn. 32 * Since it's analyzing all pathes through the program, the length of the 33 * analysis is limited to 32k insn, which may be hit even if total number of 34 * insn is less then 4K, but there are too many branches that change stack/regs. 35 * Number of 'branches to be analyzed' is limited to 1k 36 * 37 * On entry to each instruction, each register has a type, and the instruction 38 * changes the types of the registers depending on instruction semantics. 39 * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is 40 * copied to R1. 41 * 42 * All registers are 64-bit. 43 * R0 - return register 44 * R1-R5 argument passing registers 45 * R6-R9 callee saved registers 46 * R10 - frame pointer read-only 47 * 48 * At the start of BPF program the register R1 contains a pointer to bpf_context 49 * and has type PTR_TO_CTX. 50 * 51 * Verifier tracks arithmetic operations on pointers in case: 52 * BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), 53 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20), 54 * 1st insn copies R10 (which has FRAME_PTR) type into R1 55 * and 2nd arithmetic instruction is pattern matched to recognize 56 * that it wants to construct a pointer to some element within stack. 57 * So after 2nd insn, the register R1 has type PTR_TO_STACK 58 * (and -20 constant is saved for further stack bounds checking). 59 * Meaning that this reg is a pointer to stack plus known immediate constant. 60 * 61 * Most of the time the registers have UNKNOWN_VALUE type, which 62 * means the register has some value, but it's not a valid pointer. 63 * (like pointer plus pointer becomes UNKNOWN_VALUE type) 64 * 65 * When verifier sees load or store instructions the type of base register 66 * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, FRAME_PTR. These are three pointer 67 * types recognized by check_mem_access() function. 68 * 69 * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value' 70 * and the range of [ptr, ptr + map's value_size) is accessible. 71 * 72 * registers used to pass values to function calls are checked against 73 * function argument constraints. 74 * 75 * ARG_PTR_TO_MAP_KEY is one of such argument constraints. 76 * It means that the register type passed to this function must be 77 * PTR_TO_STACK and it will be used inside the function as 78 * 'pointer to map element key' 79 * 80 * For example the argument constraints for bpf_map_lookup_elem(): 81 * .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, 82 * .arg1_type = ARG_CONST_MAP_PTR, 83 * .arg2_type = ARG_PTR_TO_MAP_KEY, 84 * 85 * ret_type says that this function returns 'pointer to map elem value or null' 86 * function expects 1st argument to be a const pointer to 'struct bpf_map' and 87 * 2nd argument should be a pointer to stack, which will be used inside 88 * the helper function as a pointer to map element key. 89 * 90 * On the kernel side the helper function looks like: 91 * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) 92 * { 93 * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1; 94 * void *key = (void *) (unsigned long) r2; 95 * void *value; 96 * 97 * here kernel can access 'key' and 'map' pointers safely, knowing that 98 * [key, key + map->key_size) bytes are valid and were initialized on 99 * the stack of eBPF program. 100 * } 101 * 102 * Corresponding eBPF program may look like: 103 * BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR 104 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK 105 * BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP 106 * BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), 107 * here verifier looks at prototype of map_lookup_elem() and sees: 108 * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok, 109 * Now verifier knows that this map has key of R1->map_ptr->key_size bytes 110 * 111 * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far, 112 * Now verifier checks that [R2, R2 + map's key_size) are within stack limits 113 * and were initialized prior to this call. 114 * If it's ok, then verifier allows this BPF_CALL insn and looks at 115 * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets 116 * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function 117 * returns ether pointer to map value or NULL. 118 * 119 * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off' 120 * insn, the register holding that pointer in the true branch changes state to 121 * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false 122 * branch. See check_cond_jmp_op(). 123 * 124 * After the call R0 is set to return type of the function and registers R1-R5 125 * are set to NOT_INIT to indicate that they are no longer readable. 126 */ 127 128 /* types of values stored in eBPF registers */ 129 enum bpf_reg_type { 130 NOT_INIT = 0, /* nothing was written into register */ 131 UNKNOWN_VALUE, /* reg doesn't contain a valid pointer */ 132 PTR_TO_CTX, /* reg points to bpf_context */ 133 CONST_PTR_TO_MAP, /* reg points to struct bpf_map */ 134 PTR_TO_MAP_VALUE, /* reg points to map element value */ 135 PTR_TO_MAP_VALUE_OR_NULL,/* points to map elem value or NULL */ 136 FRAME_PTR, /* reg == frame_pointer */ 137 PTR_TO_STACK, /* reg == frame_pointer + imm */ 138 CONST_IMM, /* constant integer value */ 139 }; 140 141 struct reg_state { 142 enum bpf_reg_type type; 143 union { 144 /* valid when type == CONST_IMM | PTR_TO_STACK */ 145 int imm; 146 147 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE | 148 * PTR_TO_MAP_VALUE_OR_NULL 149 */ 150 struct bpf_map *map_ptr; 151 }; 152 }; 153 154 enum bpf_stack_slot_type { 155 STACK_INVALID, /* nothing was stored in this stack slot */ 156 STACK_SPILL, /* register spilled into stack */ 157 STACK_MISC /* BPF program wrote some data into this slot */ 158 }; 159 160 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */ 161 162 /* state of the program: 163 * type of all registers and stack info 164 */ 165 struct verifier_state { 166 struct reg_state regs[MAX_BPF_REG]; 167 u8 stack_slot_type[MAX_BPF_STACK]; 168 struct reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE]; 169 }; 170 171 /* linked list of verifier states used to prune search */ 172 struct verifier_state_list { 173 struct verifier_state state; 174 struct verifier_state_list *next; 175 }; 176 177 /* verifier_state + insn_idx are pushed to stack when branch is encountered */ 178 struct verifier_stack_elem { 179 /* verifer state is 'st' 180 * before processing instruction 'insn_idx' 181 * and after processing instruction 'prev_insn_idx' 182 */ 183 struct verifier_state st; 184 int insn_idx; 185 int prev_insn_idx; 186 struct verifier_stack_elem *next; 187 }; 188 189 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */ 190 191 /* single container for all structs 192 * one verifier_env per bpf_check() call 193 */ 194 struct verifier_env { 195 struct bpf_prog *prog; /* eBPF program being verified */ 196 struct verifier_stack_elem *head; /* stack of verifier states to be processed */ 197 int stack_size; /* number of states to be processed */ 198 struct verifier_state cur_state; /* current verifier state */ 199 struct verifier_state_list **explored_states; /* search pruning optimization */ 200 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */ 201 u32 used_map_cnt; /* number of used maps */ 202 bool allow_ptr_leaks; 203 }; 204 205 /* verbose verifier prints what it's seeing 206 * bpf_check() is called under lock, so no race to access these global vars 207 */ 208 static u32 log_level, log_size, log_len; 209 static char *log_buf; 210 211 static DEFINE_MUTEX(bpf_verifier_lock); 212 213 /* log_level controls verbosity level of eBPF verifier. 214 * verbose() is used to dump the verification trace to the log, so the user 215 * can figure out what's wrong with the program 216 */ 217 static __printf(1, 2) void verbose(const char *fmt, ...) 218 { 219 va_list args; 220 221 if (log_level == 0 || log_len >= log_size - 1) 222 return; 223 224 va_start(args, fmt); 225 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args); 226 va_end(args); 227 } 228 229 /* string representation of 'enum bpf_reg_type' */ 230 static const char * const reg_type_str[] = { 231 [NOT_INIT] = "?", 232 [UNKNOWN_VALUE] = "inv", 233 [PTR_TO_CTX] = "ctx", 234 [CONST_PTR_TO_MAP] = "map_ptr", 235 [PTR_TO_MAP_VALUE] = "map_value", 236 [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null", 237 [FRAME_PTR] = "fp", 238 [PTR_TO_STACK] = "fp", 239 [CONST_IMM] = "imm", 240 }; 241 242 static const struct { 243 int map_type; 244 int func_id; 245 } func_limit[] = { 246 {BPF_MAP_TYPE_PROG_ARRAY, BPF_FUNC_tail_call}, 247 {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_read}, 248 {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_output}, 249 }; 250 251 static void print_verifier_state(struct verifier_env *env) 252 { 253 enum bpf_reg_type t; 254 int i; 255 256 for (i = 0; i < MAX_BPF_REG; i++) { 257 t = env->cur_state.regs[i].type; 258 if (t == NOT_INIT) 259 continue; 260 verbose(" R%d=%s", i, reg_type_str[t]); 261 if (t == CONST_IMM || t == PTR_TO_STACK) 262 verbose("%d", env->cur_state.regs[i].imm); 263 else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE || 264 t == PTR_TO_MAP_VALUE_OR_NULL) 265 verbose("(ks=%d,vs=%d)", 266 env->cur_state.regs[i].map_ptr->key_size, 267 env->cur_state.regs[i].map_ptr->value_size); 268 } 269 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 270 if (env->cur_state.stack_slot_type[i] == STACK_SPILL) 271 verbose(" fp%d=%s", -MAX_BPF_STACK + i, 272 reg_type_str[env->cur_state.spilled_regs[i / BPF_REG_SIZE].type]); 273 } 274 verbose("\n"); 275 } 276 277 static const char *const bpf_class_string[] = { 278 [BPF_LD] = "ld", 279 [BPF_LDX] = "ldx", 280 [BPF_ST] = "st", 281 [BPF_STX] = "stx", 282 [BPF_ALU] = "alu", 283 [BPF_JMP] = "jmp", 284 [BPF_RET] = "BUG", 285 [BPF_ALU64] = "alu64", 286 }; 287 288 static const char *const bpf_alu_string[16] = { 289 [BPF_ADD >> 4] = "+=", 290 [BPF_SUB >> 4] = "-=", 291 [BPF_MUL >> 4] = "*=", 292 [BPF_DIV >> 4] = "/=", 293 [BPF_OR >> 4] = "|=", 294 [BPF_AND >> 4] = "&=", 295 [BPF_LSH >> 4] = "<<=", 296 [BPF_RSH >> 4] = ">>=", 297 [BPF_NEG >> 4] = "neg", 298 [BPF_MOD >> 4] = "%=", 299 [BPF_XOR >> 4] = "^=", 300 [BPF_MOV >> 4] = "=", 301 [BPF_ARSH >> 4] = "s>>=", 302 [BPF_END >> 4] = "endian", 303 }; 304 305 static const char *const bpf_ldst_string[] = { 306 [BPF_W >> 3] = "u32", 307 [BPF_H >> 3] = "u16", 308 [BPF_B >> 3] = "u8", 309 [BPF_DW >> 3] = "u64", 310 }; 311 312 static const char *const bpf_jmp_string[16] = { 313 [BPF_JA >> 4] = "jmp", 314 [BPF_JEQ >> 4] = "==", 315 [BPF_JGT >> 4] = ">", 316 [BPF_JGE >> 4] = ">=", 317 [BPF_JSET >> 4] = "&", 318 [BPF_JNE >> 4] = "!=", 319 [BPF_JSGT >> 4] = "s>", 320 [BPF_JSGE >> 4] = "s>=", 321 [BPF_CALL >> 4] = "call", 322 [BPF_EXIT >> 4] = "exit", 323 }; 324 325 static void print_bpf_insn(struct bpf_insn *insn) 326 { 327 u8 class = BPF_CLASS(insn->code); 328 329 if (class == BPF_ALU || class == BPF_ALU64) { 330 if (BPF_SRC(insn->code) == BPF_X) 331 verbose("(%02x) %sr%d %s %sr%d\n", 332 insn->code, class == BPF_ALU ? "(u32) " : "", 333 insn->dst_reg, 334 bpf_alu_string[BPF_OP(insn->code) >> 4], 335 class == BPF_ALU ? "(u32) " : "", 336 insn->src_reg); 337 else 338 verbose("(%02x) %sr%d %s %s%d\n", 339 insn->code, class == BPF_ALU ? "(u32) " : "", 340 insn->dst_reg, 341 bpf_alu_string[BPF_OP(insn->code) >> 4], 342 class == BPF_ALU ? "(u32) " : "", 343 insn->imm); 344 } else if (class == BPF_STX) { 345 if (BPF_MODE(insn->code) == BPF_MEM) 346 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n", 347 insn->code, 348 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 349 insn->dst_reg, 350 insn->off, insn->src_reg); 351 else if (BPF_MODE(insn->code) == BPF_XADD) 352 verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n", 353 insn->code, 354 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 355 insn->dst_reg, insn->off, 356 insn->src_reg); 357 else 358 verbose("BUG_%02x\n", insn->code); 359 } else if (class == BPF_ST) { 360 if (BPF_MODE(insn->code) != BPF_MEM) { 361 verbose("BUG_st_%02x\n", insn->code); 362 return; 363 } 364 verbose("(%02x) *(%s *)(r%d %+d) = %d\n", 365 insn->code, 366 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 367 insn->dst_reg, 368 insn->off, insn->imm); 369 } else if (class == BPF_LDX) { 370 if (BPF_MODE(insn->code) != BPF_MEM) { 371 verbose("BUG_ldx_%02x\n", insn->code); 372 return; 373 } 374 verbose("(%02x) r%d = *(%s *)(r%d %+d)\n", 375 insn->code, insn->dst_reg, 376 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 377 insn->src_reg, insn->off); 378 } else if (class == BPF_LD) { 379 if (BPF_MODE(insn->code) == BPF_ABS) { 380 verbose("(%02x) r0 = *(%s *)skb[%d]\n", 381 insn->code, 382 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 383 insn->imm); 384 } else if (BPF_MODE(insn->code) == BPF_IND) { 385 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n", 386 insn->code, 387 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 388 insn->src_reg, insn->imm); 389 } else if (BPF_MODE(insn->code) == BPF_IMM) { 390 verbose("(%02x) r%d = 0x%x\n", 391 insn->code, insn->dst_reg, insn->imm); 392 } else { 393 verbose("BUG_ld_%02x\n", insn->code); 394 return; 395 } 396 } else if (class == BPF_JMP) { 397 u8 opcode = BPF_OP(insn->code); 398 399 if (opcode == BPF_CALL) { 400 verbose("(%02x) call %d\n", insn->code, insn->imm); 401 } else if (insn->code == (BPF_JMP | BPF_JA)) { 402 verbose("(%02x) goto pc%+d\n", 403 insn->code, insn->off); 404 } else if (insn->code == (BPF_JMP | BPF_EXIT)) { 405 verbose("(%02x) exit\n", insn->code); 406 } else if (BPF_SRC(insn->code) == BPF_X) { 407 verbose("(%02x) if r%d %s r%d goto pc%+d\n", 408 insn->code, insn->dst_reg, 409 bpf_jmp_string[BPF_OP(insn->code) >> 4], 410 insn->src_reg, insn->off); 411 } else { 412 verbose("(%02x) if r%d %s 0x%x goto pc%+d\n", 413 insn->code, insn->dst_reg, 414 bpf_jmp_string[BPF_OP(insn->code) >> 4], 415 insn->imm, insn->off); 416 } 417 } else { 418 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]); 419 } 420 } 421 422 static int pop_stack(struct verifier_env *env, int *prev_insn_idx) 423 { 424 struct verifier_stack_elem *elem; 425 int insn_idx; 426 427 if (env->head == NULL) 428 return -1; 429 430 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state)); 431 insn_idx = env->head->insn_idx; 432 if (prev_insn_idx) 433 *prev_insn_idx = env->head->prev_insn_idx; 434 elem = env->head->next; 435 kfree(env->head); 436 env->head = elem; 437 env->stack_size--; 438 return insn_idx; 439 } 440 441 static struct verifier_state *push_stack(struct verifier_env *env, int insn_idx, 442 int prev_insn_idx) 443 { 444 struct verifier_stack_elem *elem; 445 446 elem = kmalloc(sizeof(struct verifier_stack_elem), GFP_KERNEL); 447 if (!elem) 448 goto err; 449 450 memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state)); 451 elem->insn_idx = insn_idx; 452 elem->prev_insn_idx = prev_insn_idx; 453 elem->next = env->head; 454 env->head = elem; 455 env->stack_size++; 456 if (env->stack_size > 1024) { 457 verbose("BPF program is too complex\n"); 458 goto err; 459 } 460 return &elem->st; 461 err: 462 /* pop all elements and return */ 463 while (pop_stack(env, NULL) >= 0); 464 return NULL; 465 } 466 467 #define CALLER_SAVED_REGS 6 468 static const int caller_saved[CALLER_SAVED_REGS] = { 469 BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5 470 }; 471 472 static void init_reg_state(struct reg_state *regs) 473 { 474 int i; 475 476 for (i = 0; i < MAX_BPF_REG; i++) { 477 regs[i].type = NOT_INIT; 478 regs[i].imm = 0; 479 regs[i].map_ptr = NULL; 480 } 481 482 /* frame pointer */ 483 regs[BPF_REG_FP].type = FRAME_PTR; 484 485 /* 1st arg to a function */ 486 regs[BPF_REG_1].type = PTR_TO_CTX; 487 } 488 489 static void mark_reg_unknown_value(struct reg_state *regs, u32 regno) 490 { 491 BUG_ON(regno >= MAX_BPF_REG); 492 regs[regno].type = UNKNOWN_VALUE; 493 regs[regno].imm = 0; 494 regs[regno].map_ptr = NULL; 495 } 496 497 enum reg_arg_type { 498 SRC_OP, /* register is used as source operand */ 499 DST_OP, /* register is used as destination operand */ 500 DST_OP_NO_MARK /* same as above, check only, don't mark */ 501 }; 502 503 static int check_reg_arg(struct reg_state *regs, u32 regno, 504 enum reg_arg_type t) 505 { 506 if (regno >= MAX_BPF_REG) { 507 verbose("R%d is invalid\n", regno); 508 return -EINVAL; 509 } 510 511 if (t == SRC_OP) { 512 /* check whether register used as source operand can be read */ 513 if (regs[regno].type == NOT_INIT) { 514 verbose("R%d !read_ok\n", regno); 515 return -EACCES; 516 } 517 } else { 518 /* check whether register used as dest operand can be written to */ 519 if (regno == BPF_REG_FP) { 520 verbose("frame pointer is read only\n"); 521 return -EACCES; 522 } 523 if (t == DST_OP) 524 mark_reg_unknown_value(regs, regno); 525 } 526 return 0; 527 } 528 529 static int bpf_size_to_bytes(int bpf_size) 530 { 531 if (bpf_size == BPF_W) 532 return 4; 533 else if (bpf_size == BPF_H) 534 return 2; 535 else if (bpf_size == BPF_B) 536 return 1; 537 else if (bpf_size == BPF_DW) 538 return 8; 539 else 540 return -EINVAL; 541 } 542 543 static bool is_spillable_regtype(enum bpf_reg_type type) 544 { 545 switch (type) { 546 case PTR_TO_MAP_VALUE: 547 case PTR_TO_MAP_VALUE_OR_NULL: 548 case PTR_TO_STACK: 549 case PTR_TO_CTX: 550 case FRAME_PTR: 551 case CONST_PTR_TO_MAP: 552 return true; 553 default: 554 return false; 555 } 556 } 557 558 /* check_stack_read/write functions track spill/fill of registers, 559 * stack boundary and alignment are checked in check_mem_access() 560 */ 561 static int check_stack_write(struct verifier_state *state, int off, int size, 562 int value_regno) 563 { 564 int i; 565 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0, 566 * so it's aligned access and [off, off + size) are within stack limits 567 */ 568 569 if (value_regno >= 0 && 570 is_spillable_regtype(state->regs[value_regno].type)) { 571 572 /* register containing pointer is being spilled into stack */ 573 if (size != BPF_REG_SIZE) { 574 verbose("invalid size of register spill\n"); 575 return -EACCES; 576 } 577 578 /* save register state */ 579 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = 580 state->regs[value_regno]; 581 582 for (i = 0; i < BPF_REG_SIZE; i++) 583 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL; 584 } else { 585 /* regular write of data into stack */ 586 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = 587 (struct reg_state) {}; 588 589 for (i = 0; i < size; i++) 590 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC; 591 } 592 return 0; 593 } 594 595 static int check_stack_read(struct verifier_state *state, int off, int size, 596 int value_regno) 597 { 598 u8 *slot_type; 599 int i; 600 601 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off]; 602 603 if (slot_type[0] == STACK_SPILL) { 604 if (size != BPF_REG_SIZE) { 605 verbose("invalid size of register spill\n"); 606 return -EACCES; 607 } 608 for (i = 1; i < BPF_REG_SIZE; i++) { 609 if (slot_type[i] != STACK_SPILL) { 610 verbose("corrupted spill memory\n"); 611 return -EACCES; 612 } 613 } 614 615 if (value_regno >= 0) 616 /* restore register state from stack */ 617 state->regs[value_regno] = 618 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE]; 619 return 0; 620 } else { 621 for (i = 0; i < size; i++) { 622 if (slot_type[i] != STACK_MISC) { 623 verbose("invalid read from stack off %d+%d size %d\n", 624 off, i, size); 625 return -EACCES; 626 } 627 } 628 if (value_regno >= 0) 629 /* have read misc data from the stack */ 630 mark_reg_unknown_value(state->regs, value_regno); 631 return 0; 632 } 633 } 634 635 /* check read/write into map element returned by bpf_map_lookup_elem() */ 636 static int check_map_access(struct verifier_env *env, u32 regno, int off, 637 int size) 638 { 639 struct bpf_map *map = env->cur_state.regs[regno].map_ptr; 640 641 if (off < 0 || off + size > map->value_size) { 642 verbose("invalid access to map value, value_size=%d off=%d size=%d\n", 643 map->value_size, off, size); 644 return -EACCES; 645 } 646 return 0; 647 } 648 649 /* check access to 'struct bpf_context' fields */ 650 static int check_ctx_access(struct verifier_env *env, int off, int size, 651 enum bpf_access_type t) 652 { 653 if (env->prog->aux->ops->is_valid_access && 654 env->prog->aux->ops->is_valid_access(off, size, t)) 655 return 0; 656 657 verbose("invalid bpf_context access off=%d size=%d\n", off, size); 658 return -EACCES; 659 } 660 661 static bool is_pointer_value(struct verifier_env *env, int regno) 662 { 663 if (env->allow_ptr_leaks) 664 return false; 665 666 switch (env->cur_state.regs[regno].type) { 667 case UNKNOWN_VALUE: 668 case CONST_IMM: 669 return false; 670 default: 671 return true; 672 } 673 } 674 675 /* check whether memory at (regno + off) is accessible for t = (read | write) 676 * if t==write, value_regno is a register which value is stored into memory 677 * if t==read, value_regno is a register which will receive the value from memory 678 * if t==write && value_regno==-1, some unknown value is stored into memory 679 * if t==read && value_regno==-1, don't care what we read from memory 680 */ 681 static int check_mem_access(struct verifier_env *env, u32 regno, int off, 682 int bpf_size, enum bpf_access_type t, 683 int value_regno) 684 { 685 struct verifier_state *state = &env->cur_state; 686 int size, err = 0; 687 688 if (state->regs[regno].type == PTR_TO_STACK) 689 off += state->regs[regno].imm; 690 691 size = bpf_size_to_bytes(bpf_size); 692 if (size < 0) 693 return size; 694 695 if (off % size != 0) { 696 verbose("misaligned access off %d size %d\n", off, size); 697 return -EACCES; 698 } 699 700 if (state->regs[regno].type == PTR_TO_MAP_VALUE) { 701 if (t == BPF_WRITE && value_regno >= 0 && 702 is_pointer_value(env, value_regno)) { 703 verbose("R%d leaks addr into map\n", value_regno); 704 return -EACCES; 705 } 706 err = check_map_access(env, regno, off, size); 707 if (!err && t == BPF_READ && value_regno >= 0) 708 mark_reg_unknown_value(state->regs, value_regno); 709 710 } else if (state->regs[regno].type == PTR_TO_CTX) { 711 if (t == BPF_WRITE && value_regno >= 0 && 712 is_pointer_value(env, value_regno)) { 713 verbose("R%d leaks addr into ctx\n", value_regno); 714 return -EACCES; 715 } 716 err = check_ctx_access(env, off, size, t); 717 if (!err && t == BPF_READ && value_regno >= 0) 718 mark_reg_unknown_value(state->regs, value_regno); 719 720 } else if (state->regs[regno].type == FRAME_PTR || 721 state->regs[regno].type == PTR_TO_STACK) { 722 if (off >= 0 || off < -MAX_BPF_STACK) { 723 verbose("invalid stack off=%d size=%d\n", off, size); 724 return -EACCES; 725 } 726 if (t == BPF_WRITE) { 727 if (!env->allow_ptr_leaks && 728 state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL && 729 size != BPF_REG_SIZE) { 730 verbose("attempt to corrupt spilled pointer on stack\n"); 731 return -EACCES; 732 } 733 err = check_stack_write(state, off, size, value_regno); 734 } else { 735 err = check_stack_read(state, off, size, value_regno); 736 } 737 } else { 738 verbose("R%d invalid mem access '%s'\n", 739 regno, reg_type_str[state->regs[regno].type]); 740 return -EACCES; 741 } 742 return err; 743 } 744 745 static int check_xadd(struct verifier_env *env, struct bpf_insn *insn) 746 { 747 struct reg_state *regs = env->cur_state.regs; 748 int err; 749 750 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) || 751 insn->imm != 0) { 752 verbose("BPF_XADD uses reserved fields\n"); 753 return -EINVAL; 754 } 755 756 /* check src1 operand */ 757 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 758 if (err) 759 return err; 760 761 /* check src2 operand */ 762 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 763 if (err) 764 return err; 765 766 /* check whether atomic_add can read the memory */ 767 err = check_mem_access(env, insn->dst_reg, insn->off, 768 BPF_SIZE(insn->code), BPF_READ, -1); 769 if (err) 770 return err; 771 772 /* check whether atomic_add can write into the same memory */ 773 return check_mem_access(env, insn->dst_reg, insn->off, 774 BPF_SIZE(insn->code), BPF_WRITE, -1); 775 } 776 777 /* when register 'regno' is passed into function that will read 'access_size' 778 * bytes from that pointer, make sure that it's within stack boundary 779 * and all elements of stack are initialized 780 */ 781 static int check_stack_boundary(struct verifier_env *env, 782 int regno, int access_size) 783 { 784 struct verifier_state *state = &env->cur_state; 785 struct reg_state *regs = state->regs; 786 int off, i; 787 788 if (regs[regno].type != PTR_TO_STACK) 789 return -EACCES; 790 791 off = regs[regno].imm; 792 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 || 793 access_size <= 0) { 794 verbose("invalid stack type R%d off=%d access_size=%d\n", 795 regno, off, access_size); 796 return -EACCES; 797 } 798 799 for (i = 0; i < access_size; i++) { 800 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) { 801 verbose("invalid indirect read from stack off %d+%d size %d\n", 802 off, i, access_size); 803 return -EACCES; 804 } 805 } 806 return 0; 807 } 808 809 static int check_func_arg(struct verifier_env *env, u32 regno, 810 enum bpf_arg_type arg_type, struct bpf_map **mapp) 811 { 812 struct reg_state *reg = env->cur_state.regs + regno; 813 enum bpf_reg_type expected_type; 814 int err = 0; 815 816 if (arg_type == ARG_DONTCARE) 817 return 0; 818 819 if (reg->type == NOT_INIT) { 820 verbose("R%d !read_ok\n", regno); 821 return -EACCES; 822 } 823 824 if (arg_type == ARG_ANYTHING) { 825 if (is_pointer_value(env, regno)) { 826 verbose("R%d leaks addr into helper function\n", regno); 827 return -EACCES; 828 } 829 return 0; 830 } 831 832 if (arg_type == ARG_PTR_TO_STACK || arg_type == ARG_PTR_TO_MAP_KEY || 833 arg_type == ARG_PTR_TO_MAP_VALUE) { 834 expected_type = PTR_TO_STACK; 835 } else if (arg_type == ARG_CONST_STACK_SIZE) { 836 expected_type = CONST_IMM; 837 } else if (arg_type == ARG_CONST_MAP_PTR) { 838 expected_type = CONST_PTR_TO_MAP; 839 } else if (arg_type == ARG_PTR_TO_CTX) { 840 expected_type = PTR_TO_CTX; 841 } else { 842 verbose("unsupported arg_type %d\n", arg_type); 843 return -EFAULT; 844 } 845 846 if (reg->type != expected_type) { 847 verbose("R%d type=%s expected=%s\n", regno, 848 reg_type_str[reg->type], reg_type_str[expected_type]); 849 return -EACCES; 850 } 851 852 if (arg_type == ARG_CONST_MAP_PTR) { 853 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */ 854 *mapp = reg->map_ptr; 855 856 } else if (arg_type == ARG_PTR_TO_MAP_KEY) { 857 /* bpf_map_xxx(..., map_ptr, ..., key) call: 858 * check that [key, key + map->key_size) are within 859 * stack limits and initialized 860 */ 861 if (!*mapp) { 862 /* in function declaration map_ptr must come before 863 * map_key, so that it's verified and known before 864 * we have to check map_key here. Otherwise it means 865 * that kernel subsystem misconfigured verifier 866 */ 867 verbose("invalid map_ptr to access map->key\n"); 868 return -EACCES; 869 } 870 err = check_stack_boundary(env, regno, (*mapp)->key_size); 871 872 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) { 873 /* bpf_map_xxx(..., map_ptr, ..., value) call: 874 * check [value, value + map->value_size) validity 875 */ 876 if (!*mapp) { 877 /* kernel subsystem misconfigured verifier */ 878 verbose("invalid map_ptr to access map->value\n"); 879 return -EACCES; 880 } 881 err = check_stack_boundary(env, regno, (*mapp)->value_size); 882 883 } else if (arg_type == ARG_CONST_STACK_SIZE) { 884 /* bpf_xxx(..., buf, len) call will access 'len' bytes 885 * from stack pointer 'buf'. Check it 886 * note: regno == len, regno - 1 == buf 887 */ 888 if (regno == 0) { 889 /* kernel subsystem misconfigured verifier */ 890 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n"); 891 return -EACCES; 892 } 893 err = check_stack_boundary(env, regno - 1, reg->imm); 894 } 895 896 return err; 897 } 898 899 static int check_map_func_compatibility(struct bpf_map *map, int func_id) 900 { 901 bool bool_map, bool_func; 902 int i; 903 904 if (!map) 905 return 0; 906 907 for (i = 0; i < ARRAY_SIZE(func_limit); i++) { 908 bool_map = (map->map_type == func_limit[i].map_type); 909 bool_func = (func_id == func_limit[i].func_id); 910 /* only when map & func pair match it can continue. 911 * don't allow any other map type to be passed into 912 * the special func; 913 */ 914 if (bool_func && bool_map != bool_func) 915 return -EINVAL; 916 } 917 918 return 0; 919 } 920 921 static int check_call(struct verifier_env *env, int func_id) 922 { 923 struct verifier_state *state = &env->cur_state; 924 const struct bpf_func_proto *fn = NULL; 925 struct reg_state *regs = state->regs; 926 struct bpf_map *map = NULL; 927 struct reg_state *reg; 928 int i, err; 929 930 /* find function prototype */ 931 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) { 932 verbose("invalid func %d\n", func_id); 933 return -EINVAL; 934 } 935 936 if (env->prog->aux->ops->get_func_proto) 937 fn = env->prog->aux->ops->get_func_proto(func_id); 938 939 if (!fn) { 940 verbose("unknown func %d\n", func_id); 941 return -EINVAL; 942 } 943 944 /* eBPF programs must be GPL compatible to use GPL-ed functions */ 945 if (!env->prog->gpl_compatible && fn->gpl_only) { 946 verbose("cannot call GPL only function from proprietary program\n"); 947 return -EINVAL; 948 } 949 950 /* check args */ 951 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &map); 952 if (err) 953 return err; 954 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &map); 955 if (err) 956 return err; 957 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &map); 958 if (err) 959 return err; 960 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &map); 961 if (err) 962 return err; 963 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &map); 964 if (err) 965 return err; 966 967 /* reset caller saved regs */ 968 for (i = 0; i < CALLER_SAVED_REGS; i++) { 969 reg = regs + caller_saved[i]; 970 reg->type = NOT_INIT; 971 reg->imm = 0; 972 } 973 974 /* update return register */ 975 if (fn->ret_type == RET_INTEGER) { 976 regs[BPF_REG_0].type = UNKNOWN_VALUE; 977 } else if (fn->ret_type == RET_VOID) { 978 regs[BPF_REG_0].type = NOT_INIT; 979 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) { 980 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL; 981 /* remember map_ptr, so that check_map_access() 982 * can check 'value_size' boundary of memory access 983 * to map element returned from bpf_map_lookup_elem() 984 */ 985 if (map == NULL) { 986 verbose("kernel subsystem misconfigured verifier\n"); 987 return -EINVAL; 988 } 989 regs[BPF_REG_0].map_ptr = map; 990 } else { 991 verbose("unknown return type %d of func %d\n", 992 fn->ret_type, func_id); 993 return -EINVAL; 994 } 995 996 err = check_map_func_compatibility(map, func_id); 997 if (err) 998 return err; 999 1000 return 0; 1001 } 1002 1003 /* check validity of 32-bit and 64-bit arithmetic operations */ 1004 static int check_alu_op(struct verifier_env *env, struct bpf_insn *insn) 1005 { 1006 struct reg_state *regs = env->cur_state.regs; 1007 u8 opcode = BPF_OP(insn->code); 1008 int err; 1009 1010 if (opcode == BPF_END || opcode == BPF_NEG) { 1011 if (opcode == BPF_NEG) { 1012 if (BPF_SRC(insn->code) != 0 || 1013 insn->src_reg != BPF_REG_0 || 1014 insn->off != 0 || insn->imm != 0) { 1015 verbose("BPF_NEG uses reserved fields\n"); 1016 return -EINVAL; 1017 } 1018 } else { 1019 if (insn->src_reg != BPF_REG_0 || insn->off != 0 || 1020 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) { 1021 verbose("BPF_END uses reserved fields\n"); 1022 return -EINVAL; 1023 } 1024 } 1025 1026 /* check src operand */ 1027 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1028 if (err) 1029 return err; 1030 1031 if (is_pointer_value(env, insn->dst_reg)) { 1032 verbose("R%d pointer arithmetic prohibited\n", 1033 insn->dst_reg); 1034 return -EACCES; 1035 } 1036 1037 /* check dest operand */ 1038 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1039 if (err) 1040 return err; 1041 1042 } else if (opcode == BPF_MOV) { 1043 1044 if (BPF_SRC(insn->code) == BPF_X) { 1045 if (insn->imm != 0 || insn->off != 0) { 1046 verbose("BPF_MOV uses reserved fields\n"); 1047 return -EINVAL; 1048 } 1049 1050 /* check src operand */ 1051 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1052 if (err) 1053 return err; 1054 } else { 1055 if (insn->src_reg != BPF_REG_0 || insn->off != 0) { 1056 verbose("BPF_MOV uses reserved fields\n"); 1057 return -EINVAL; 1058 } 1059 } 1060 1061 /* check dest operand */ 1062 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1063 if (err) 1064 return err; 1065 1066 if (BPF_SRC(insn->code) == BPF_X) { 1067 if (BPF_CLASS(insn->code) == BPF_ALU64) { 1068 /* case: R1 = R2 1069 * copy register state to dest reg 1070 */ 1071 regs[insn->dst_reg] = regs[insn->src_reg]; 1072 } else { 1073 if (is_pointer_value(env, insn->src_reg)) { 1074 verbose("R%d partial copy of pointer\n", 1075 insn->src_reg); 1076 return -EACCES; 1077 } 1078 regs[insn->dst_reg].type = UNKNOWN_VALUE; 1079 regs[insn->dst_reg].map_ptr = NULL; 1080 } 1081 } else { 1082 /* case: R = imm 1083 * remember the value we stored into this reg 1084 */ 1085 regs[insn->dst_reg].type = CONST_IMM; 1086 regs[insn->dst_reg].imm = insn->imm; 1087 } 1088 1089 } else if (opcode > BPF_END) { 1090 verbose("invalid BPF_ALU opcode %x\n", opcode); 1091 return -EINVAL; 1092 1093 } else { /* all other ALU ops: and, sub, xor, add, ... */ 1094 1095 bool stack_relative = false; 1096 1097 if (BPF_SRC(insn->code) == BPF_X) { 1098 if (insn->imm != 0 || insn->off != 0) { 1099 verbose("BPF_ALU uses reserved fields\n"); 1100 return -EINVAL; 1101 } 1102 /* check src1 operand */ 1103 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1104 if (err) 1105 return err; 1106 } else { 1107 if (insn->src_reg != BPF_REG_0 || insn->off != 0) { 1108 verbose("BPF_ALU uses reserved fields\n"); 1109 return -EINVAL; 1110 } 1111 } 1112 1113 /* check src2 operand */ 1114 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1115 if (err) 1116 return err; 1117 1118 if ((opcode == BPF_MOD || opcode == BPF_DIV) && 1119 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) { 1120 verbose("div by zero\n"); 1121 return -EINVAL; 1122 } 1123 1124 /* pattern match 'bpf_add Rx, imm' instruction */ 1125 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 && 1126 regs[insn->dst_reg].type == FRAME_PTR && 1127 BPF_SRC(insn->code) == BPF_K) { 1128 stack_relative = true; 1129 } else if (is_pointer_value(env, insn->dst_reg)) { 1130 verbose("R%d pointer arithmetic prohibited\n", 1131 insn->dst_reg); 1132 return -EACCES; 1133 } else if (BPF_SRC(insn->code) == BPF_X && 1134 is_pointer_value(env, insn->src_reg)) { 1135 verbose("R%d pointer arithmetic prohibited\n", 1136 insn->src_reg); 1137 return -EACCES; 1138 } 1139 1140 /* check dest operand */ 1141 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1142 if (err) 1143 return err; 1144 1145 if (stack_relative) { 1146 regs[insn->dst_reg].type = PTR_TO_STACK; 1147 regs[insn->dst_reg].imm = insn->imm; 1148 } 1149 } 1150 1151 return 0; 1152 } 1153 1154 static int check_cond_jmp_op(struct verifier_env *env, 1155 struct bpf_insn *insn, int *insn_idx) 1156 { 1157 struct reg_state *regs = env->cur_state.regs; 1158 struct verifier_state *other_branch; 1159 u8 opcode = BPF_OP(insn->code); 1160 int err; 1161 1162 if (opcode > BPF_EXIT) { 1163 verbose("invalid BPF_JMP opcode %x\n", opcode); 1164 return -EINVAL; 1165 } 1166 1167 if (BPF_SRC(insn->code) == BPF_X) { 1168 if (insn->imm != 0) { 1169 verbose("BPF_JMP uses reserved fields\n"); 1170 return -EINVAL; 1171 } 1172 1173 /* check src1 operand */ 1174 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1175 if (err) 1176 return err; 1177 1178 if (is_pointer_value(env, insn->src_reg)) { 1179 verbose("R%d pointer comparison prohibited\n", 1180 insn->src_reg); 1181 return -EACCES; 1182 } 1183 } else { 1184 if (insn->src_reg != BPF_REG_0) { 1185 verbose("BPF_JMP uses reserved fields\n"); 1186 return -EINVAL; 1187 } 1188 } 1189 1190 /* check src2 operand */ 1191 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1192 if (err) 1193 return err; 1194 1195 /* detect if R == 0 where R was initialized to zero earlier */ 1196 if (BPF_SRC(insn->code) == BPF_K && 1197 (opcode == BPF_JEQ || opcode == BPF_JNE) && 1198 regs[insn->dst_reg].type == CONST_IMM && 1199 regs[insn->dst_reg].imm == insn->imm) { 1200 if (opcode == BPF_JEQ) { 1201 /* if (imm == imm) goto pc+off; 1202 * only follow the goto, ignore fall-through 1203 */ 1204 *insn_idx += insn->off; 1205 return 0; 1206 } else { 1207 /* if (imm != imm) goto pc+off; 1208 * only follow fall-through branch, since 1209 * that's where the program will go 1210 */ 1211 return 0; 1212 } 1213 } 1214 1215 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx); 1216 if (!other_branch) 1217 return -EFAULT; 1218 1219 /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */ 1220 if (BPF_SRC(insn->code) == BPF_K && 1221 insn->imm == 0 && (opcode == BPF_JEQ || 1222 opcode == BPF_JNE) && 1223 regs[insn->dst_reg].type == PTR_TO_MAP_VALUE_OR_NULL) { 1224 if (opcode == BPF_JEQ) { 1225 /* next fallthrough insn can access memory via 1226 * this register 1227 */ 1228 regs[insn->dst_reg].type = PTR_TO_MAP_VALUE; 1229 /* branch targer cannot access it, since reg == 0 */ 1230 other_branch->regs[insn->dst_reg].type = CONST_IMM; 1231 other_branch->regs[insn->dst_reg].imm = 0; 1232 } else { 1233 other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE; 1234 regs[insn->dst_reg].type = CONST_IMM; 1235 regs[insn->dst_reg].imm = 0; 1236 } 1237 } else if (is_pointer_value(env, insn->dst_reg)) { 1238 verbose("R%d pointer comparison prohibited\n", insn->dst_reg); 1239 return -EACCES; 1240 } else if (BPF_SRC(insn->code) == BPF_K && 1241 (opcode == BPF_JEQ || opcode == BPF_JNE)) { 1242 1243 if (opcode == BPF_JEQ) { 1244 /* detect if (R == imm) goto 1245 * and in the target state recognize that R = imm 1246 */ 1247 other_branch->regs[insn->dst_reg].type = CONST_IMM; 1248 other_branch->regs[insn->dst_reg].imm = insn->imm; 1249 } else { 1250 /* detect if (R != imm) goto 1251 * and in the fall-through state recognize that R = imm 1252 */ 1253 regs[insn->dst_reg].type = CONST_IMM; 1254 regs[insn->dst_reg].imm = insn->imm; 1255 } 1256 } 1257 if (log_level) 1258 print_verifier_state(env); 1259 return 0; 1260 } 1261 1262 /* return the map pointer stored inside BPF_LD_IMM64 instruction */ 1263 static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn) 1264 { 1265 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32; 1266 1267 return (struct bpf_map *) (unsigned long) imm64; 1268 } 1269 1270 /* verify BPF_LD_IMM64 instruction */ 1271 static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn) 1272 { 1273 struct reg_state *regs = env->cur_state.regs; 1274 int err; 1275 1276 if (BPF_SIZE(insn->code) != BPF_DW) { 1277 verbose("invalid BPF_LD_IMM insn\n"); 1278 return -EINVAL; 1279 } 1280 if (insn->off != 0) { 1281 verbose("BPF_LD_IMM64 uses reserved fields\n"); 1282 return -EINVAL; 1283 } 1284 1285 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1286 if (err) 1287 return err; 1288 1289 if (insn->src_reg == 0) 1290 /* generic move 64-bit immediate into a register */ 1291 return 0; 1292 1293 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */ 1294 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD); 1295 1296 regs[insn->dst_reg].type = CONST_PTR_TO_MAP; 1297 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn); 1298 return 0; 1299 } 1300 1301 static bool may_access_skb(enum bpf_prog_type type) 1302 { 1303 switch (type) { 1304 case BPF_PROG_TYPE_SOCKET_FILTER: 1305 case BPF_PROG_TYPE_SCHED_CLS: 1306 case BPF_PROG_TYPE_SCHED_ACT: 1307 return true; 1308 default: 1309 return false; 1310 } 1311 } 1312 1313 /* verify safety of LD_ABS|LD_IND instructions: 1314 * - they can only appear in the programs where ctx == skb 1315 * - since they are wrappers of function calls, they scratch R1-R5 registers, 1316 * preserve R6-R9, and store return value into R0 1317 * 1318 * Implicit input: 1319 * ctx == skb == R6 == CTX 1320 * 1321 * Explicit input: 1322 * SRC == any register 1323 * IMM == 32-bit immediate 1324 * 1325 * Output: 1326 * R0 - 8/16/32-bit skb data converted to cpu endianness 1327 */ 1328 static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn) 1329 { 1330 struct reg_state *regs = env->cur_state.regs; 1331 u8 mode = BPF_MODE(insn->code); 1332 struct reg_state *reg; 1333 int i, err; 1334 1335 if (!may_access_skb(env->prog->type)) { 1336 verbose("BPF_LD_ABS|IND instructions not allowed for this program type\n"); 1337 return -EINVAL; 1338 } 1339 1340 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 || 1341 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) { 1342 verbose("BPF_LD_ABS uses reserved fields\n"); 1343 return -EINVAL; 1344 } 1345 1346 /* check whether implicit source operand (register R6) is readable */ 1347 err = check_reg_arg(regs, BPF_REG_6, SRC_OP); 1348 if (err) 1349 return err; 1350 1351 if (regs[BPF_REG_6].type != PTR_TO_CTX) { 1352 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n"); 1353 return -EINVAL; 1354 } 1355 1356 if (mode == BPF_IND) { 1357 /* check explicit source operand */ 1358 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1359 if (err) 1360 return err; 1361 } 1362 1363 /* reset caller saved regs to unreadable */ 1364 for (i = 0; i < CALLER_SAVED_REGS; i++) { 1365 reg = regs + caller_saved[i]; 1366 reg->type = NOT_INIT; 1367 reg->imm = 0; 1368 } 1369 1370 /* mark destination R0 register as readable, since it contains 1371 * the value fetched from the packet 1372 */ 1373 regs[BPF_REG_0].type = UNKNOWN_VALUE; 1374 return 0; 1375 } 1376 1377 /* non-recursive DFS pseudo code 1378 * 1 procedure DFS-iterative(G,v): 1379 * 2 label v as discovered 1380 * 3 let S be a stack 1381 * 4 S.push(v) 1382 * 5 while S is not empty 1383 * 6 t <- S.pop() 1384 * 7 if t is what we're looking for: 1385 * 8 return t 1386 * 9 for all edges e in G.adjacentEdges(t) do 1387 * 10 if edge e is already labelled 1388 * 11 continue with the next edge 1389 * 12 w <- G.adjacentVertex(t,e) 1390 * 13 if vertex w is not discovered and not explored 1391 * 14 label e as tree-edge 1392 * 15 label w as discovered 1393 * 16 S.push(w) 1394 * 17 continue at 5 1395 * 18 else if vertex w is discovered 1396 * 19 label e as back-edge 1397 * 20 else 1398 * 21 // vertex w is explored 1399 * 22 label e as forward- or cross-edge 1400 * 23 label t as explored 1401 * 24 S.pop() 1402 * 1403 * convention: 1404 * 0x10 - discovered 1405 * 0x11 - discovered and fall-through edge labelled 1406 * 0x12 - discovered and fall-through and branch edges labelled 1407 * 0x20 - explored 1408 */ 1409 1410 enum { 1411 DISCOVERED = 0x10, 1412 EXPLORED = 0x20, 1413 FALLTHROUGH = 1, 1414 BRANCH = 2, 1415 }; 1416 1417 #define STATE_LIST_MARK ((struct verifier_state_list *) -1L) 1418 1419 static int *insn_stack; /* stack of insns to process */ 1420 static int cur_stack; /* current stack index */ 1421 static int *insn_state; 1422 1423 /* t, w, e - match pseudo-code above: 1424 * t - index of current instruction 1425 * w - next instruction 1426 * e - edge 1427 */ 1428 static int push_insn(int t, int w, int e, struct verifier_env *env) 1429 { 1430 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH)) 1431 return 0; 1432 1433 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH)) 1434 return 0; 1435 1436 if (w < 0 || w >= env->prog->len) { 1437 verbose("jump out of range from insn %d to %d\n", t, w); 1438 return -EINVAL; 1439 } 1440 1441 if (e == BRANCH) 1442 /* mark branch target for state pruning */ 1443 env->explored_states[w] = STATE_LIST_MARK; 1444 1445 if (insn_state[w] == 0) { 1446 /* tree-edge */ 1447 insn_state[t] = DISCOVERED | e; 1448 insn_state[w] = DISCOVERED; 1449 if (cur_stack >= env->prog->len) 1450 return -E2BIG; 1451 insn_stack[cur_stack++] = w; 1452 return 1; 1453 } else if ((insn_state[w] & 0xF0) == DISCOVERED) { 1454 verbose("back-edge from insn %d to %d\n", t, w); 1455 return -EINVAL; 1456 } else if (insn_state[w] == EXPLORED) { 1457 /* forward- or cross-edge */ 1458 insn_state[t] = DISCOVERED | e; 1459 } else { 1460 verbose("insn state internal bug\n"); 1461 return -EFAULT; 1462 } 1463 return 0; 1464 } 1465 1466 /* non-recursive depth-first-search to detect loops in BPF program 1467 * loop == back-edge in directed graph 1468 */ 1469 static int check_cfg(struct verifier_env *env) 1470 { 1471 struct bpf_insn *insns = env->prog->insnsi; 1472 int insn_cnt = env->prog->len; 1473 int ret = 0; 1474 int i, t; 1475 1476 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 1477 if (!insn_state) 1478 return -ENOMEM; 1479 1480 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 1481 if (!insn_stack) { 1482 kfree(insn_state); 1483 return -ENOMEM; 1484 } 1485 1486 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */ 1487 insn_stack[0] = 0; /* 0 is the first instruction */ 1488 cur_stack = 1; 1489 1490 peek_stack: 1491 if (cur_stack == 0) 1492 goto check_state; 1493 t = insn_stack[cur_stack - 1]; 1494 1495 if (BPF_CLASS(insns[t].code) == BPF_JMP) { 1496 u8 opcode = BPF_OP(insns[t].code); 1497 1498 if (opcode == BPF_EXIT) { 1499 goto mark_explored; 1500 } else if (opcode == BPF_CALL) { 1501 ret = push_insn(t, t + 1, FALLTHROUGH, env); 1502 if (ret == 1) 1503 goto peek_stack; 1504 else if (ret < 0) 1505 goto err_free; 1506 } else if (opcode == BPF_JA) { 1507 if (BPF_SRC(insns[t].code) != BPF_K) { 1508 ret = -EINVAL; 1509 goto err_free; 1510 } 1511 /* unconditional jump with single edge */ 1512 ret = push_insn(t, t + insns[t].off + 1, 1513 FALLTHROUGH, env); 1514 if (ret == 1) 1515 goto peek_stack; 1516 else if (ret < 0) 1517 goto err_free; 1518 /* tell verifier to check for equivalent states 1519 * after every call and jump 1520 */ 1521 if (t + 1 < insn_cnt) 1522 env->explored_states[t + 1] = STATE_LIST_MARK; 1523 } else { 1524 /* conditional jump with two edges */ 1525 ret = push_insn(t, t + 1, FALLTHROUGH, env); 1526 if (ret == 1) 1527 goto peek_stack; 1528 else if (ret < 0) 1529 goto err_free; 1530 1531 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env); 1532 if (ret == 1) 1533 goto peek_stack; 1534 else if (ret < 0) 1535 goto err_free; 1536 } 1537 } else { 1538 /* all other non-branch instructions with single 1539 * fall-through edge 1540 */ 1541 ret = push_insn(t, t + 1, FALLTHROUGH, env); 1542 if (ret == 1) 1543 goto peek_stack; 1544 else if (ret < 0) 1545 goto err_free; 1546 } 1547 1548 mark_explored: 1549 insn_state[t] = EXPLORED; 1550 if (cur_stack-- <= 0) { 1551 verbose("pop stack internal bug\n"); 1552 ret = -EFAULT; 1553 goto err_free; 1554 } 1555 goto peek_stack; 1556 1557 check_state: 1558 for (i = 0; i < insn_cnt; i++) { 1559 if (insn_state[i] != EXPLORED) { 1560 verbose("unreachable insn %d\n", i); 1561 ret = -EINVAL; 1562 goto err_free; 1563 } 1564 } 1565 ret = 0; /* cfg looks good */ 1566 1567 err_free: 1568 kfree(insn_state); 1569 kfree(insn_stack); 1570 return ret; 1571 } 1572 1573 /* compare two verifier states 1574 * 1575 * all states stored in state_list are known to be valid, since 1576 * verifier reached 'bpf_exit' instruction through them 1577 * 1578 * this function is called when verifier exploring different branches of 1579 * execution popped from the state stack. If it sees an old state that has 1580 * more strict register state and more strict stack state then this execution 1581 * branch doesn't need to be explored further, since verifier already 1582 * concluded that more strict state leads to valid finish. 1583 * 1584 * Therefore two states are equivalent if register state is more conservative 1585 * and explored stack state is more conservative than the current one. 1586 * Example: 1587 * explored current 1588 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC) 1589 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC) 1590 * 1591 * In other words if current stack state (one being explored) has more 1592 * valid slots than old one that already passed validation, it means 1593 * the verifier can stop exploring and conclude that current state is valid too 1594 * 1595 * Similarly with registers. If explored state has register type as invalid 1596 * whereas register type in current state is meaningful, it means that 1597 * the current state will reach 'bpf_exit' instruction safely 1598 */ 1599 static bool states_equal(struct verifier_state *old, struct verifier_state *cur) 1600 { 1601 int i; 1602 1603 for (i = 0; i < MAX_BPF_REG; i++) { 1604 if (memcmp(&old->regs[i], &cur->regs[i], 1605 sizeof(old->regs[0])) != 0) { 1606 if (old->regs[i].type == NOT_INIT || 1607 (old->regs[i].type == UNKNOWN_VALUE && 1608 cur->regs[i].type != NOT_INIT)) 1609 continue; 1610 return false; 1611 } 1612 } 1613 1614 for (i = 0; i < MAX_BPF_STACK; i++) { 1615 if (old->stack_slot_type[i] == STACK_INVALID) 1616 continue; 1617 if (old->stack_slot_type[i] != cur->stack_slot_type[i]) 1618 /* Ex: old explored (safe) state has STACK_SPILL in 1619 * this stack slot, but current has has STACK_MISC -> 1620 * this verifier states are not equivalent, 1621 * return false to continue verification of this path 1622 */ 1623 return false; 1624 if (i % BPF_REG_SIZE) 1625 continue; 1626 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE], 1627 &cur->spilled_regs[i / BPF_REG_SIZE], 1628 sizeof(old->spilled_regs[0]))) 1629 /* when explored and current stack slot types are 1630 * the same, check that stored pointers types 1631 * are the same as well. 1632 * Ex: explored safe path could have stored 1633 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8} 1634 * but current path has stored: 1635 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16} 1636 * such verifier states are not equivalent. 1637 * return false to continue verification of this path 1638 */ 1639 return false; 1640 else 1641 continue; 1642 } 1643 return true; 1644 } 1645 1646 static int is_state_visited(struct verifier_env *env, int insn_idx) 1647 { 1648 struct verifier_state_list *new_sl; 1649 struct verifier_state_list *sl; 1650 1651 sl = env->explored_states[insn_idx]; 1652 if (!sl) 1653 /* this 'insn_idx' instruction wasn't marked, so we will not 1654 * be doing state search here 1655 */ 1656 return 0; 1657 1658 while (sl != STATE_LIST_MARK) { 1659 if (states_equal(&sl->state, &env->cur_state)) 1660 /* reached equivalent register/stack state, 1661 * prune the search 1662 */ 1663 return 1; 1664 sl = sl->next; 1665 } 1666 1667 /* there were no equivalent states, remember current one. 1668 * technically the current state is not proven to be safe yet, 1669 * but it will either reach bpf_exit (which means it's safe) or 1670 * it will be rejected. Since there are no loops, we won't be 1671 * seeing this 'insn_idx' instruction again on the way to bpf_exit 1672 */ 1673 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER); 1674 if (!new_sl) 1675 return -ENOMEM; 1676 1677 /* add new state to the head of linked list */ 1678 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state)); 1679 new_sl->next = env->explored_states[insn_idx]; 1680 env->explored_states[insn_idx] = new_sl; 1681 return 0; 1682 } 1683 1684 static int do_check(struct verifier_env *env) 1685 { 1686 struct verifier_state *state = &env->cur_state; 1687 struct bpf_insn *insns = env->prog->insnsi; 1688 struct reg_state *regs = state->regs; 1689 int insn_cnt = env->prog->len; 1690 int insn_idx, prev_insn_idx = 0; 1691 int insn_processed = 0; 1692 bool do_print_state = false; 1693 1694 init_reg_state(regs); 1695 insn_idx = 0; 1696 for (;;) { 1697 struct bpf_insn *insn; 1698 u8 class; 1699 int err; 1700 1701 if (insn_idx >= insn_cnt) { 1702 verbose("invalid insn idx %d insn_cnt %d\n", 1703 insn_idx, insn_cnt); 1704 return -EFAULT; 1705 } 1706 1707 insn = &insns[insn_idx]; 1708 class = BPF_CLASS(insn->code); 1709 1710 if (++insn_processed > 32768) { 1711 verbose("BPF program is too large. Proccessed %d insn\n", 1712 insn_processed); 1713 return -E2BIG; 1714 } 1715 1716 err = is_state_visited(env, insn_idx); 1717 if (err < 0) 1718 return err; 1719 if (err == 1) { 1720 /* found equivalent state, can prune the search */ 1721 if (log_level) { 1722 if (do_print_state) 1723 verbose("\nfrom %d to %d: safe\n", 1724 prev_insn_idx, insn_idx); 1725 else 1726 verbose("%d: safe\n", insn_idx); 1727 } 1728 goto process_bpf_exit; 1729 } 1730 1731 if (log_level && do_print_state) { 1732 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx); 1733 print_verifier_state(env); 1734 do_print_state = false; 1735 } 1736 1737 if (log_level) { 1738 verbose("%d: ", insn_idx); 1739 print_bpf_insn(insn); 1740 } 1741 1742 if (class == BPF_ALU || class == BPF_ALU64) { 1743 err = check_alu_op(env, insn); 1744 if (err) 1745 return err; 1746 1747 } else if (class == BPF_LDX) { 1748 enum bpf_reg_type src_reg_type; 1749 1750 /* check for reserved fields is already done */ 1751 1752 /* check src operand */ 1753 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1754 if (err) 1755 return err; 1756 1757 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); 1758 if (err) 1759 return err; 1760 1761 src_reg_type = regs[insn->src_reg].type; 1762 1763 /* check that memory (src_reg + off) is readable, 1764 * the state of dst_reg will be updated by this func 1765 */ 1766 err = check_mem_access(env, insn->src_reg, insn->off, 1767 BPF_SIZE(insn->code), BPF_READ, 1768 insn->dst_reg); 1769 if (err) 1770 return err; 1771 1772 if (BPF_SIZE(insn->code) != BPF_W) { 1773 insn_idx++; 1774 continue; 1775 } 1776 1777 if (insn->imm == 0) { 1778 /* saw a valid insn 1779 * dst_reg = *(u32 *)(src_reg + off) 1780 * use reserved 'imm' field to mark this insn 1781 */ 1782 insn->imm = src_reg_type; 1783 1784 } else if (src_reg_type != insn->imm && 1785 (src_reg_type == PTR_TO_CTX || 1786 insn->imm == PTR_TO_CTX)) { 1787 /* ABuser program is trying to use the same insn 1788 * dst_reg = *(u32*) (src_reg + off) 1789 * with different pointer types: 1790 * src_reg == ctx in one branch and 1791 * src_reg == stack|map in some other branch. 1792 * Reject it. 1793 */ 1794 verbose("same insn cannot be used with different pointers\n"); 1795 return -EINVAL; 1796 } 1797 1798 } else if (class == BPF_STX) { 1799 enum bpf_reg_type dst_reg_type; 1800 1801 if (BPF_MODE(insn->code) == BPF_XADD) { 1802 err = check_xadd(env, insn); 1803 if (err) 1804 return err; 1805 insn_idx++; 1806 continue; 1807 } 1808 1809 /* check src1 operand */ 1810 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1811 if (err) 1812 return err; 1813 /* check src2 operand */ 1814 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1815 if (err) 1816 return err; 1817 1818 dst_reg_type = regs[insn->dst_reg].type; 1819 1820 /* check that memory (dst_reg + off) is writeable */ 1821 err = check_mem_access(env, insn->dst_reg, insn->off, 1822 BPF_SIZE(insn->code), BPF_WRITE, 1823 insn->src_reg); 1824 if (err) 1825 return err; 1826 1827 if (insn->imm == 0) { 1828 insn->imm = dst_reg_type; 1829 } else if (dst_reg_type != insn->imm && 1830 (dst_reg_type == PTR_TO_CTX || 1831 insn->imm == PTR_TO_CTX)) { 1832 verbose("same insn cannot be used with different pointers\n"); 1833 return -EINVAL; 1834 } 1835 1836 } else if (class == BPF_ST) { 1837 if (BPF_MODE(insn->code) != BPF_MEM || 1838 insn->src_reg != BPF_REG_0) { 1839 verbose("BPF_ST uses reserved fields\n"); 1840 return -EINVAL; 1841 } 1842 /* check src operand */ 1843 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1844 if (err) 1845 return err; 1846 1847 /* check that memory (dst_reg + off) is writeable */ 1848 err = check_mem_access(env, insn->dst_reg, insn->off, 1849 BPF_SIZE(insn->code), BPF_WRITE, 1850 -1); 1851 if (err) 1852 return err; 1853 1854 } else if (class == BPF_JMP) { 1855 u8 opcode = BPF_OP(insn->code); 1856 1857 if (opcode == BPF_CALL) { 1858 if (BPF_SRC(insn->code) != BPF_K || 1859 insn->off != 0 || 1860 insn->src_reg != BPF_REG_0 || 1861 insn->dst_reg != BPF_REG_0) { 1862 verbose("BPF_CALL uses reserved fields\n"); 1863 return -EINVAL; 1864 } 1865 1866 err = check_call(env, insn->imm); 1867 if (err) 1868 return err; 1869 1870 } else if (opcode == BPF_JA) { 1871 if (BPF_SRC(insn->code) != BPF_K || 1872 insn->imm != 0 || 1873 insn->src_reg != BPF_REG_0 || 1874 insn->dst_reg != BPF_REG_0) { 1875 verbose("BPF_JA uses reserved fields\n"); 1876 return -EINVAL; 1877 } 1878 1879 insn_idx += insn->off + 1; 1880 continue; 1881 1882 } else if (opcode == BPF_EXIT) { 1883 if (BPF_SRC(insn->code) != BPF_K || 1884 insn->imm != 0 || 1885 insn->src_reg != BPF_REG_0 || 1886 insn->dst_reg != BPF_REG_0) { 1887 verbose("BPF_EXIT uses reserved fields\n"); 1888 return -EINVAL; 1889 } 1890 1891 /* eBPF calling convetion is such that R0 is used 1892 * to return the value from eBPF program. 1893 * Make sure that it's readable at this time 1894 * of bpf_exit, which means that program wrote 1895 * something into it earlier 1896 */ 1897 err = check_reg_arg(regs, BPF_REG_0, SRC_OP); 1898 if (err) 1899 return err; 1900 1901 if (is_pointer_value(env, BPF_REG_0)) { 1902 verbose("R0 leaks addr as return value\n"); 1903 return -EACCES; 1904 } 1905 1906 process_bpf_exit: 1907 insn_idx = pop_stack(env, &prev_insn_idx); 1908 if (insn_idx < 0) { 1909 break; 1910 } else { 1911 do_print_state = true; 1912 continue; 1913 } 1914 } else { 1915 err = check_cond_jmp_op(env, insn, &insn_idx); 1916 if (err) 1917 return err; 1918 } 1919 } else if (class == BPF_LD) { 1920 u8 mode = BPF_MODE(insn->code); 1921 1922 if (mode == BPF_ABS || mode == BPF_IND) { 1923 err = check_ld_abs(env, insn); 1924 if (err) 1925 return err; 1926 1927 } else if (mode == BPF_IMM) { 1928 err = check_ld_imm(env, insn); 1929 if (err) 1930 return err; 1931 1932 insn_idx++; 1933 } else { 1934 verbose("invalid BPF_LD mode\n"); 1935 return -EINVAL; 1936 } 1937 } else { 1938 verbose("unknown insn class %d\n", class); 1939 return -EINVAL; 1940 } 1941 1942 insn_idx++; 1943 } 1944 1945 return 0; 1946 } 1947 1948 /* look for pseudo eBPF instructions that access map FDs and 1949 * replace them with actual map pointers 1950 */ 1951 static int replace_map_fd_with_map_ptr(struct verifier_env *env) 1952 { 1953 struct bpf_insn *insn = env->prog->insnsi; 1954 int insn_cnt = env->prog->len; 1955 int i, j; 1956 1957 for (i = 0; i < insn_cnt; i++, insn++) { 1958 if (BPF_CLASS(insn->code) == BPF_LDX && 1959 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) { 1960 verbose("BPF_LDX uses reserved fields\n"); 1961 return -EINVAL; 1962 } 1963 1964 if (BPF_CLASS(insn->code) == BPF_STX && 1965 ((BPF_MODE(insn->code) != BPF_MEM && 1966 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) { 1967 verbose("BPF_STX uses reserved fields\n"); 1968 return -EINVAL; 1969 } 1970 1971 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) { 1972 struct bpf_map *map; 1973 struct fd f; 1974 1975 if (i == insn_cnt - 1 || insn[1].code != 0 || 1976 insn[1].dst_reg != 0 || insn[1].src_reg != 0 || 1977 insn[1].off != 0) { 1978 verbose("invalid bpf_ld_imm64 insn\n"); 1979 return -EINVAL; 1980 } 1981 1982 if (insn->src_reg == 0) 1983 /* valid generic load 64-bit imm */ 1984 goto next_insn; 1985 1986 if (insn->src_reg != BPF_PSEUDO_MAP_FD) { 1987 verbose("unrecognized bpf_ld_imm64 insn\n"); 1988 return -EINVAL; 1989 } 1990 1991 f = fdget(insn->imm); 1992 map = __bpf_map_get(f); 1993 if (IS_ERR(map)) { 1994 verbose("fd %d is not pointing to valid bpf_map\n", 1995 insn->imm); 1996 fdput(f); 1997 return PTR_ERR(map); 1998 } 1999 2000 /* store map pointer inside BPF_LD_IMM64 instruction */ 2001 insn[0].imm = (u32) (unsigned long) map; 2002 insn[1].imm = ((u64) (unsigned long) map) >> 32; 2003 2004 /* check whether we recorded this map already */ 2005 for (j = 0; j < env->used_map_cnt; j++) 2006 if (env->used_maps[j] == map) { 2007 fdput(f); 2008 goto next_insn; 2009 } 2010 2011 if (env->used_map_cnt >= MAX_USED_MAPS) { 2012 fdput(f); 2013 return -E2BIG; 2014 } 2015 2016 /* remember this map */ 2017 env->used_maps[env->used_map_cnt++] = map; 2018 2019 /* hold the map. If the program is rejected by verifier, 2020 * the map will be released by release_maps() or it 2021 * will be used by the valid program until it's unloaded 2022 * and all maps are released in free_bpf_prog_info() 2023 */ 2024 atomic_inc(&map->refcnt); 2025 2026 fdput(f); 2027 next_insn: 2028 insn++; 2029 i++; 2030 } 2031 } 2032 2033 /* now all pseudo BPF_LD_IMM64 instructions load valid 2034 * 'struct bpf_map *' into a register instead of user map_fd. 2035 * These pointers will be used later by verifier to validate map access. 2036 */ 2037 return 0; 2038 } 2039 2040 /* drop refcnt of maps used by the rejected program */ 2041 static void release_maps(struct verifier_env *env) 2042 { 2043 int i; 2044 2045 for (i = 0; i < env->used_map_cnt; i++) 2046 bpf_map_put(env->used_maps[i]); 2047 } 2048 2049 /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */ 2050 static void convert_pseudo_ld_imm64(struct verifier_env *env) 2051 { 2052 struct bpf_insn *insn = env->prog->insnsi; 2053 int insn_cnt = env->prog->len; 2054 int i; 2055 2056 for (i = 0; i < insn_cnt; i++, insn++) 2057 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW)) 2058 insn->src_reg = 0; 2059 } 2060 2061 static void adjust_branches(struct bpf_prog *prog, int pos, int delta) 2062 { 2063 struct bpf_insn *insn = prog->insnsi; 2064 int insn_cnt = prog->len; 2065 int i; 2066 2067 for (i = 0; i < insn_cnt; i++, insn++) { 2068 if (BPF_CLASS(insn->code) != BPF_JMP || 2069 BPF_OP(insn->code) == BPF_CALL || 2070 BPF_OP(insn->code) == BPF_EXIT) 2071 continue; 2072 2073 /* adjust offset of jmps if necessary */ 2074 if (i < pos && i + insn->off + 1 > pos) 2075 insn->off += delta; 2076 else if (i > pos && i + insn->off + 1 < pos) 2077 insn->off -= delta; 2078 } 2079 } 2080 2081 /* convert load instructions that access fields of 'struct __sk_buff' 2082 * into sequence of instructions that access fields of 'struct sk_buff' 2083 */ 2084 static int convert_ctx_accesses(struct verifier_env *env) 2085 { 2086 struct bpf_insn *insn = env->prog->insnsi; 2087 int insn_cnt = env->prog->len; 2088 struct bpf_insn insn_buf[16]; 2089 struct bpf_prog *new_prog; 2090 u32 cnt; 2091 int i; 2092 enum bpf_access_type type; 2093 2094 if (!env->prog->aux->ops->convert_ctx_access) 2095 return 0; 2096 2097 for (i = 0; i < insn_cnt; i++, insn++) { 2098 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W)) 2099 type = BPF_READ; 2100 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W)) 2101 type = BPF_WRITE; 2102 else 2103 continue; 2104 2105 if (insn->imm != PTR_TO_CTX) { 2106 /* clear internal mark */ 2107 insn->imm = 0; 2108 continue; 2109 } 2110 2111 cnt = env->prog->aux->ops-> 2112 convert_ctx_access(type, insn->dst_reg, insn->src_reg, 2113 insn->off, insn_buf, env->prog); 2114 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) { 2115 verbose("bpf verifier is misconfigured\n"); 2116 return -EINVAL; 2117 } 2118 2119 if (cnt == 1) { 2120 memcpy(insn, insn_buf, sizeof(*insn)); 2121 continue; 2122 } 2123 2124 /* several new insns need to be inserted. Make room for them */ 2125 insn_cnt += cnt - 1; 2126 new_prog = bpf_prog_realloc(env->prog, 2127 bpf_prog_size(insn_cnt), 2128 GFP_USER); 2129 if (!new_prog) 2130 return -ENOMEM; 2131 2132 new_prog->len = insn_cnt; 2133 2134 memmove(new_prog->insnsi + i + cnt, new_prog->insns + i + 1, 2135 sizeof(*insn) * (insn_cnt - i - cnt)); 2136 2137 /* copy substitute insns in place of load instruction */ 2138 memcpy(new_prog->insnsi + i, insn_buf, sizeof(*insn) * cnt); 2139 2140 /* adjust branches in the whole program */ 2141 adjust_branches(new_prog, i, cnt - 1); 2142 2143 /* keep walking new program and skip insns we just inserted */ 2144 env->prog = new_prog; 2145 insn = new_prog->insnsi + i + cnt - 1; 2146 i += cnt - 1; 2147 } 2148 2149 return 0; 2150 } 2151 2152 static void free_states(struct verifier_env *env) 2153 { 2154 struct verifier_state_list *sl, *sln; 2155 int i; 2156 2157 if (!env->explored_states) 2158 return; 2159 2160 for (i = 0; i < env->prog->len; i++) { 2161 sl = env->explored_states[i]; 2162 2163 if (sl) 2164 while (sl != STATE_LIST_MARK) { 2165 sln = sl->next; 2166 kfree(sl); 2167 sl = sln; 2168 } 2169 } 2170 2171 kfree(env->explored_states); 2172 } 2173 2174 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) 2175 { 2176 char __user *log_ubuf = NULL; 2177 struct verifier_env *env; 2178 int ret = -EINVAL; 2179 2180 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS) 2181 return -E2BIG; 2182 2183 /* 'struct verifier_env' can be global, but since it's not small, 2184 * allocate/free it every time bpf_check() is called 2185 */ 2186 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL); 2187 if (!env) 2188 return -ENOMEM; 2189 2190 env->prog = *prog; 2191 2192 /* grab the mutex to protect few globals used by verifier */ 2193 mutex_lock(&bpf_verifier_lock); 2194 2195 if (attr->log_level || attr->log_buf || attr->log_size) { 2196 /* user requested verbose verifier output 2197 * and supplied buffer to store the verification trace 2198 */ 2199 log_level = attr->log_level; 2200 log_ubuf = (char __user *) (unsigned long) attr->log_buf; 2201 log_size = attr->log_size; 2202 log_len = 0; 2203 2204 ret = -EINVAL; 2205 /* log_* values have to be sane */ 2206 if (log_size < 128 || log_size > UINT_MAX >> 8 || 2207 log_level == 0 || log_ubuf == NULL) 2208 goto free_env; 2209 2210 ret = -ENOMEM; 2211 log_buf = vmalloc(log_size); 2212 if (!log_buf) 2213 goto free_env; 2214 } else { 2215 log_level = 0; 2216 } 2217 2218 ret = replace_map_fd_with_map_ptr(env); 2219 if (ret < 0) 2220 goto skip_full_check; 2221 2222 env->explored_states = kcalloc(env->prog->len, 2223 sizeof(struct verifier_state_list *), 2224 GFP_USER); 2225 ret = -ENOMEM; 2226 if (!env->explored_states) 2227 goto skip_full_check; 2228 2229 ret = check_cfg(env); 2230 if (ret < 0) 2231 goto skip_full_check; 2232 2233 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); 2234 2235 ret = do_check(env); 2236 2237 skip_full_check: 2238 while (pop_stack(env, NULL) >= 0); 2239 free_states(env); 2240 2241 if (ret == 0) 2242 /* program is valid, convert *(u32*)(ctx + off) accesses */ 2243 ret = convert_ctx_accesses(env); 2244 2245 if (log_level && log_len >= log_size - 1) { 2246 BUG_ON(log_len >= log_size); 2247 /* verifier log exceeded user supplied buffer */ 2248 ret = -ENOSPC; 2249 /* fall through to return what was recorded */ 2250 } 2251 2252 /* copy verifier log back to user space including trailing zero */ 2253 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) { 2254 ret = -EFAULT; 2255 goto free_log_buf; 2256 } 2257 2258 if (ret == 0 && env->used_map_cnt) { 2259 /* if program passed verifier, update used_maps in bpf_prog_info */ 2260 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt, 2261 sizeof(env->used_maps[0]), 2262 GFP_KERNEL); 2263 2264 if (!env->prog->aux->used_maps) { 2265 ret = -ENOMEM; 2266 goto free_log_buf; 2267 } 2268 2269 memcpy(env->prog->aux->used_maps, env->used_maps, 2270 sizeof(env->used_maps[0]) * env->used_map_cnt); 2271 env->prog->aux->used_map_cnt = env->used_map_cnt; 2272 2273 /* program is valid. Convert pseudo bpf_ld_imm64 into generic 2274 * bpf_ld_imm64 instructions 2275 */ 2276 convert_pseudo_ld_imm64(env); 2277 } 2278 2279 free_log_buf: 2280 if (log_level) 2281 vfree(log_buf); 2282 free_env: 2283 if (!env->prog->aux->used_maps) 2284 /* if we didn't copy map pointers into bpf_prog_info, release 2285 * them now. Otherwise free_bpf_prog_info() will release them. 2286 */ 2287 release_maps(env); 2288 *prog = env->prog; 2289 kfree(env); 2290 mutex_unlock(&bpf_verifier_lock); 2291 return ret; 2292 } 2293