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