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