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 */ 129enum 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 141struct 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 154enum 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 */ 165struct 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 */ 172struct 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 */ 178struct 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 */ 194struct 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 */ 207static u32 log_level, log_size, log_len; 208static char *log_buf; 209 210static 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 */ 216static 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' */ 229static 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 241static 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 267static 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 278static 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 295static 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 302static 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 315static 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 412static 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 431static 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; 451err: 452 /* pop all elements and return */ 453 while (pop_stack(env, NULL) >= 0); 454 return NULL; 455} 456 457#define CALLER_SAVED_REGS 6 458static 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 462static 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 479static 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 487enum 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 493static 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 519static 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 */ 536static 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 572static 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() */ 613static 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 */ 627static 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 */ 644static 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 687static 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 */ 723static 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 751static 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 836static 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 */ 914static 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 if ((opcode == BPF_LSH || opcode == BPF_RSH || 1023 opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) { 1024 int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32; 1025 1026 if (insn->imm < 0 || insn->imm >= size) { 1027 verbose("invalid shift %d\n", insn->imm); 1028 return -EINVAL; 1029 } 1030 } 1031 1032 /* pattern match 'bpf_add Rx, imm' instruction */ 1033 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 && 1034 regs[insn->dst_reg].type == FRAME_PTR && 1035 BPF_SRC(insn->code) == BPF_K) 1036 stack_relative = true; 1037 1038 /* check dest operand */ 1039 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1040 if (err) 1041 return err; 1042 1043 if (stack_relative) { 1044 regs[insn->dst_reg].type = PTR_TO_STACK; 1045 regs[insn->dst_reg].imm = insn->imm; 1046 } 1047 } 1048 1049 return 0; 1050} 1051 1052static int check_cond_jmp_op(struct verifier_env *env, 1053 struct bpf_insn *insn, int *insn_idx) 1054{ 1055 struct reg_state *regs = env->cur_state.regs; 1056 struct verifier_state *other_branch; 1057 u8 opcode = BPF_OP(insn->code); 1058 int err; 1059 1060 if (opcode > BPF_EXIT) { 1061 verbose("invalid BPF_JMP opcode %x\n", opcode); 1062 return -EINVAL; 1063 } 1064 1065 if (BPF_SRC(insn->code) == BPF_X) { 1066 if (insn->imm != 0) { 1067 verbose("BPF_JMP uses reserved fields\n"); 1068 return -EINVAL; 1069 } 1070 1071 /* check src1 operand */ 1072 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1073 if (err) 1074 return err; 1075 } else { 1076 if (insn->src_reg != BPF_REG_0) { 1077 verbose("BPF_JMP uses reserved fields\n"); 1078 return -EINVAL; 1079 } 1080 } 1081 1082 /* check src2 operand */ 1083 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1084 if (err) 1085 return err; 1086 1087 /* detect if R == 0 where R was initialized to zero earlier */ 1088 if (BPF_SRC(insn->code) == BPF_K && 1089 (opcode == BPF_JEQ || opcode == BPF_JNE) && 1090 regs[insn->dst_reg].type == CONST_IMM && 1091 regs[insn->dst_reg].imm == insn->imm) { 1092 if (opcode == BPF_JEQ) { 1093 /* if (imm == imm) goto pc+off; 1094 * only follow the goto, ignore fall-through 1095 */ 1096 *insn_idx += insn->off; 1097 return 0; 1098 } else { 1099 /* if (imm != imm) goto pc+off; 1100 * only follow fall-through branch, since 1101 * that's where the program will go 1102 */ 1103 return 0; 1104 } 1105 } 1106 1107 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx); 1108 if (!other_branch) 1109 return -EFAULT; 1110 1111 /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */ 1112 if (BPF_SRC(insn->code) == BPF_K && 1113 insn->imm == 0 && (opcode == BPF_JEQ || 1114 opcode == BPF_JNE) && 1115 regs[insn->dst_reg].type == PTR_TO_MAP_VALUE_OR_NULL) { 1116 if (opcode == BPF_JEQ) { 1117 /* next fallthrough insn can access memory via 1118 * this register 1119 */ 1120 regs[insn->dst_reg].type = PTR_TO_MAP_VALUE; 1121 /* branch targer cannot access it, since reg == 0 */ 1122 other_branch->regs[insn->dst_reg].type = CONST_IMM; 1123 other_branch->regs[insn->dst_reg].imm = 0; 1124 } else { 1125 other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE; 1126 regs[insn->dst_reg].type = CONST_IMM; 1127 regs[insn->dst_reg].imm = 0; 1128 } 1129 } else if (BPF_SRC(insn->code) == BPF_K && 1130 (opcode == BPF_JEQ || opcode == BPF_JNE)) { 1131 1132 if (opcode == BPF_JEQ) { 1133 /* detect if (R == imm) goto 1134 * and in the target state recognize that R = imm 1135 */ 1136 other_branch->regs[insn->dst_reg].type = CONST_IMM; 1137 other_branch->regs[insn->dst_reg].imm = insn->imm; 1138 } else { 1139 /* detect if (R != imm) goto 1140 * and in the fall-through state recognize that R = imm 1141 */ 1142 regs[insn->dst_reg].type = CONST_IMM; 1143 regs[insn->dst_reg].imm = insn->imm; 1144 } 1145 } 1146 if (log_level) 1147 print_verifier_state(env); 1148 return 0; 1149} 1150 1151/* return the map pointer stored inside BPF_LD_IMM64 instruction */ 1152static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn) 1153{ 1154 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32; 1155 1156 return (struct bpf_map *) (unsigned long) imm64; 1157} 1158 1159/* verify BPF_LD_IMM64 instruction */ 1160static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn) 1161{ 1162 struct reg_state *regs = env->cur_state.regs; 1163 int err; 1164 1165 if (BPF_SIZE(insn->code) != BPF_DW) { 1166 verbose("invalid BPF_LD_IMM insn\n"); 1167 return -EINVAL; 1168 } 1169 if (insn->off != 0) { 1170 verbose("BPF_LD_IMM64 uses reserved fields\n"); 1171 return -EINVAL; 1172 } 1173 1174 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1175 if (err) 1176 return err; 1177 1178 if (insn->src_reg == 0) 1179 /* generic move 64-bit immediate into a register */ 1180 return 0; 1181 1182 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */ 1183 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD); 1184 1185 regs[insn->dst_reg].type = CONST_PTR_TO_MAP; 1186 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn); 1187 return 0; 1188} 1189 1190static bool may_access_skb(enum bpf_prog_type type) 1191{ 1192 switch (type) { 1193 case BPF_PROG_TYPE_SOCKET_FILTER: 1194 case BPF_PROG_TYPE_SCHED_CLS: 1195 case BPF_PROG_TYPE_SCHED_ACT: 1196 return true; 1197 default: 1198 return false; 1199 } 1200} 1201 1202/* verify safety of LD_ABS|LD_IND instructions: 1203 * - they can only appear in the programs where ctx == skb 1204 * - since they are wrappers of function calls, they scratch R1-R5 registers, 1205 * preserve R6-R9, and store return value into R0 1206 * 1207 * Implicit input: 1208 * ctx == skb == R6 == CTX 1209 * 1210 * Explicit input: 1211 * SRC == any register 1212 * IMM == 32-bit immediate 1213 * 1214 * Output: 1215 * R0 - 8/16/32-bit skb data converted to cpu endianness 1216 */ 1217static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn) 1218{ 1219 struct reg_state *regs = env->cur_state.regs; 1220 u8 mode = BPF_MODE(insn->code); 1221 struct reg_state *reg; 1222 int i, err; 1223 1224 if (!may_access_skb(env->prog->type)) { 1225 verbose("BPF_LD_ABS|IND instructions not allowed for this program type\n"); 1226 return -EINVAL; 1227 } 1228 1229 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 || 1230 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) { 1231 verbose("BPF_LD_ABS uses reserved fields\n"); 1232 return -EINVAL; 1233 } 1234 1235 /* check whether implicit source operand (register R6) is readable */ 1236 err = check_reg_arg(regs, BPF_REG_6, SRC_OP); 1237 if (err) 1238 return err; 1239 1240 if (regs[BPF_REG_6].type != PTR_TO_CTX) { 1241 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n"); 1242 return -EINVAL; 1243 } 1244 1245 if (mode == BPF_IND) { 1246 /* check explicit source operand */ 1247 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1248 if (err) 1249 return err; 1250 } 1251 1252 /* reset caller saved regs to unreadable */ 1253 for (i = 0; i < CALLER_SAVED_REGS; i++) { 1254 reg = regs + caller_saved[i]; 1255 reg->type = NOT_INIT; 1256 reg->imm = 0; 1257 } 1258 1259 /* mark destination R0 register as readable, since it contains 1260 * the value fetched from the packet 1261 */ 1262 regs[BPF_REG_0].type = UNKNOWN_VALUE; 1263 return 0; 1264} 1265 1266/* non-recursive DFS pseudo code 1267 * 1 procedure DFS-iterative(G,v): 1268 * 2 label v as discovered 1269 * 3 let S be a stack 1270 * 4 S.push(v) 1271 * 5 while S is not empty 1272 * 6 t <- S.pop() 1273 * 7 if t is what we're looking for: 1274 * 8 return t 1275 * 9 for all edges e in G.adjacentEdges(t) do 1276 * 10 if edge e is already labelled 1277 * 11 continue with the next edge 1278 * 12 w <- G.adjacentVertex(t,e) 1279 * 13 if vertex w is not discovered and not explored 1280 * 14 label e as tree-edge 1281 * 15 label w as discovered 1282 * 16 S.push(w) 1283 * 17 continue at 5 1284 * 18 else if vertex w is discovered 1285 * 19 label e as back-edge 1286 * 20 else 1287 * 21 // vertex w is explored 1288 * 22 label e as forward- or cross-edge 1289 * 23 label t as explored 1290 * 24 S.pop() 1291 * 1292 * convention: 1293 * 0x10 - discovered 1294 * 0x11 - discovered and fall-through edge labelled 1295 * 0x12 - discovered and fall-through and branch edges labelled 1296 * 0x20 - explored 1297 */ 1298 1299enum { 1300 DISCOVERED = 0x10, 1301 EXPLORED = 0x20, 1302 FALLTHROUGH = 1, 1303 BRANCH = 2, 1304}; 1305 1306#define STATE_LIST_MARK ((struct verifier_state_list *) -1L) 1307 1308static int *insn_stack; /* stack of insns to process */ 1309static int cur_stack; /* current stack index */ 1310static int *insn_state; 1311 1312/* t, w, e - match pseudo-code above: 1313 * t - index of current instruction 1314 * w - next instruction 1315 * e - edge 1316 */ 1317static int push_insn(int t, int w, int e, struct verifier_env *env) 1318{ 1319 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH)) 1320 return 0; 1321 1322 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH)) 1323 return 0; 1324 1325 if (w < 0 || w >= env->prog->len) { 1326 verbose("jump out of range from insn %d to %d\n", t, w); 1327 return -EINVAL; 1328 } 1329 1330 if (e == BRANCH) 1331 /* mark branch target for state pruning */ 1332 env->explored_states[w] = STATE_LIST_MARK; 1333 1334 if (insn_state[w] == 0) { 1335 /* tree-edge */ 1336 insn_state[t] = DISCOVERED | e; 1337 insn_state[w] = DISCOVERED; 1338 if (cur_stack >= env->prog->len) 1339 return -E2BIG; 1340 insn_stack[cur_stack++] = w; 1341 return 1; 1342 } else if ((insn_state[w] & 0xF0) == DISCOVERED) { 1343 verbose("back-edge from insn %d to %d\n", t, w); 1344 return -EINVAL; 1345 } else if (insn_state[w] == EXPLORED) { 1346 /* forward- or cross-edge */ 1347 insn_state[t] = DISCOVERED | e; 1348 } else { 1349 verbose("insn state internal bug\n"); 1350 return -EFAULT; 1351 } 1352 return 0; 1353} 1354 1355/* non-recursive depth-first-search to detect loops in BPF program 1356 * loop == back-edge in directed graph 1357 */ 1358static int check_cfg(struct verifier_env *env) 1359{ 1360 struct bpf_insn *insns = env->prog->insnsi; 1361 int insn_cnt = env->prog->len; 1362 int ret = 0; 1363 int i, t; 1364 1365 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 1366 if (!insn_state) 1367 return -ENOMEM; 1368 1369 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 1370 if (!insn_stack) { 1371 kfree(insn_state); 1372 return -ENOMEM; 1373 } 1374 1375 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */ 1376 insn_stack[0] = 0; /* 0 is the first instruction */ 1377 cur_stack = 1; 1378 1379peek_stack: 1380 if (cur_stack == 0) 1381 goto check_state; 1382 t = insn_stack[cur_stack - 1]; 1383 1384 if (BPF_CLASS(insns[t].code) == BPF_JMP) { 1385 u8 opcode = BPF_OP(insns[t].code); 1386 1387 if (opcode == BPF_EXIT) { 1388 goto mark_explored; 1389 } else if (opcode == BPF_CALL) { 1390 ret = push_insn(t, t + 1, FALLTHROUGH, env); 1391 if (ret == 1) 1392 goto peek_stack; 1393 else if (ret < 0) 1394 goto err_free; 1395 } else if (opcode == BPF_JA) { 1396 if (BPF_SRC(insns[t].code) != BPF_K) { 1397 ret = -EINVAL; 1398 goto err_free; 1399 } 1400 /* unconditional jump with single edge */ 1401 ret = push_insn(t, t + insns[t].off + 1, 1402 FALLTHROUGH, env); 1403 if (ret == 1) 1404 goto peek_stack; 1405 else if (ret < 0) 1406 goto err_free; 1407 /* tell verifier to check for equivalent states 1408 * after every call and jump 1409 */ 1410 if (t + 1 < insn_cnt) 1411 env->explored_states[t + 1] = STATE_LIST_MARK; 1412 } else { 1413 /* conditional jump with two edges */ 1414 ret = push_insn(t, t + 1, FALLTHROUGH, env); 1415 if (ret == 1) 1416 goto peek_stack; 1417 else if (ret < 0) 1418 goto err_free; 1419 1420 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env); 1421 if (ret == 1) 1422 goto peek_stack; 1423 else if (ret < 0) 1424 goto err_free; 1425 } 1426 } else { 1427 /* all other non-branch instructions with single 1428 * fall-through edge 1429 */ 1430 ret = push_insn(t, t + 1, FALLTHROUGH, env); 1431 if (ret == 1) 1432 goto peek_stack; 1433 else if (ret < 0) 1434 goto err_free; 1435 } 1436 1437mark_explored: 1438 insn_state[t] = EXPLORED; 1439 if (cur_stack-- <= 0) { 1440 verbose("pop stack internal bug\n"); 1441 ret = -EFAULT; 1442 goto err_free; 1443 } 1444 goto peek_stack; 1445 1446check_state: 1447 for (i = 0; i < insn_cnt; i++) { 1448 if (insn_state[i] != EXPLORED) { 1449 verbose("unreachable insn %d\n", i); 1450 ret = -EINVAL; 1451 goto err_free; 1452 } 1453 } 1454 ret = 0; /* cfg looks good */ 1455 1456err_free: 1457 kfree(insn_state); 1458 kfree(insn_stack); 1459 return ret; 1460} 1461 1462/* compare two verifier states 1463 * 1464 * all states stored in state_list are known to be valid, since 1465 * verifier reached 'bpf_exit' instruction through them 1466 * 1467 * this function is called when verifier exploring different branches of 1468 * execution popped from the state stack. If it sees an old state that has 1469 * more strict register state and more strict stack state then this execution 1470 * branch doesn't need to be explored further, since verifier already 1471 * concluded that more strict state leads to valid finish. 1472 * 1473 * Therefore two states are equivalent if register state is more conservative 1474 * and explored stack state is more conservative than the current one. 1475 * Example: 1476 * explored current 1477 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC) 1478 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC) 1479 * 1480 * In other words if current stack state (one being explored) has more 1481 * valid slots than old one that already passed validation, it means 1482 * the verifier can stop exploring and conclude that current state is valid too 1483 * 1484 * Similarly with registers. If explored state has register type as invalid 1485 * whereas register type in current state is meaningful, it means that 1486 * the current state will reach 'bpf_exit' instruction safely 1487 */ 1488static bool states_equal(struct verifier_state *old, struct verifier_state *cur) 1489{ 1490 int i; 1491 1492 for (i = 0; i < MAX_BPF_REG; i++) { 1493 if (memcmp(&old->regs[i], &cur->regs[i], 1494 sizeof(old->regs[0])) != 0) { 1495 if (old->regs[i].type == NOT_INIT || 1496 (old->regs[i].type == UNKNOWN_VALUE && 1497 cur->regs[i].type != NOT_INIT)) 1498 continue; 1499 return false; 1500 } 1501 } 1502 1503 for (i = 0; i < MAX_BPF_STACK; i++) { 1504 if (old->stack_slot_type[i] == STACK_INVALID) 1505 continue; 1506 if (old->stack_slot_type[i] != cur->stack_slot_type[i]) 1507 /* Ex: old explored (safe) state has STACK_SPILL in 1508 * this stack slot, but current has has STACK_MISC -> 1509 * this verifier states are not equivalent, 1510 * return false to continue verification of this path 1511 */ 1512 return false; 1513 if (i % BPF_REG_SIZE) 1514 continue; 1515 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE], 1516 &cur->spilled_regs[i / BPF_REG_SIZE], 1517 sizeof(old->spilled_regs[0]))) 1518 /* when explored and current stack slot types are 1519 * the same, check that stored pointers types 1520 * are the same as well. 1521 * Ex: explored safe path could have stored 1522 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8} 1523 * but current path has stored: 1524 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16} 1525 * such verifier states are not equivalent. 1526 * return false to continue verification of this path 1527 */ 1528 return false; 1529 else 1530 continue; 1531 } 1532 return true; 1533} 1534 1535static int is_state_visited(struct verifier_env *env, int insn_idx) 1536{ 1537 struct verifier_state_list *new_sl; 1538 struct verifier_state_list *sl; 1539 1540 sl = env->explored_states[insn_idx]; 1541 if (!sl) 1542 /* this 'insn_idx' instruction wasn't marked, so we will not 1543 * be doing state search here 1544 */ 1545 return 0; 1546 1547 while (sl != STATE_LIST_MARK) { 1548 if (states_equal(&sl->state, &env->cur_state)) 1549 /* reached equivalent register/stack state, 1550 * prune the search 1551 */ 1552 return 1; 1553 sl = sl->next; 1554 } 1555 1556 /* there were no equivalent states, remember current one. 1557 * technically the current state is not proven to be safe yet, 1558 * but it will either reach bpf_exit (which means it's safe) or 1559 * it will be rejected. Since there are no loops, we won't be 1560 * seeing this 'insn_idx' instruction again on the way to bpf_exit 1561 */ 1562 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER); 1563 if (!new_sl) 1564 return -ENOMEM; 1565 1566 /* add new state to the head of linked list */ 1567 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state)); 1568 new_sl->next = env->explored_states[insn_idx]; 1569 env->explored_states[insn_idx] = new_sl; 1570 return 0; 1571} 1572 1573static int do_check(struct verifier_env *env) 1574{ 1575 struct verifier_state *state = &env->cur_state; 1576 struct bpf_insn *insns = env->prog->insnsi; 1577 struct reg_state *regs = state->regs; 1578 int insn_cnt = env->prog->len; 1579 int insn_idx, prev_insn_idx = 0; 1580 int insn_processed = 0; 1581 bool do_print_state = false; 1582 1583 init_reg_state(regs); 1584 insn_idx = 0; 1585 for (;;) { 1586 struct bpf_insn *insn; 1587 u8 class; 1588 int err; 1589 1590 if (insn_idx >= insn_cnt) { 1591 verbose("invalid insn idx %d insn_cnt %d\n", 1592 insn_idx, insn_cnt); 1593 return -EFAULT; 1594 } 1595 1596 insn = &insns[insn_idx]; 1597 class = BPF_CLASS(insn->code); 1598 1599 if (++insn_processed > 32768) { 1600 verbose("BPF program is too large. Proccessed %d insn\n", 1601 insn_processed); 1602 return -E2BIG; 1603 } 1604 1605 err = is_state_visited(env, insn_idx); 1606 if (err < 0) 1607 return err; 1608 if (err == 1) { 1609 /* found equivalent state, can prune the search */ 1610 if (log_level) { 1611 if (do_print_state) 1612 verbose("\nfrom %d to %d: safe\n", 1613 prev_insn_idx, insn_idx); 1614 else 1615 verbose("%d: safe\n", insn_idx); 1616 } 1617 goto process_bpf_exit; 1618 } 1619 1620 if (log_level && do_print_state) { 1621 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx); 1622 print_verifier_state(env); 1623 do_print_state = false; 1624 } 1625 1626 if (log_level) { 1627 verbose("%d: ", insn_idx); 1628 print_bpf_insn(insn); 1629 } 1630 1631 if (class == BPF_ALU || class == BPF_ALU64) { 1632 err = check_alu_op(regs, insn); 1633 if (err) 1634 return err; 1635 1636 } else if (class == BPF_LDX) { 1637 enum bpf_reg_type src_reg_type; 1638 1639 /* check for reserved fields is already done */ 1640 1641 /* check src operand */ 1642 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1643 if (err) 1644 return err; 1645 1646 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); 1647 if (err) 1648 return err; 1649 1650 src_reg_type = regs[insn->src_reg].type; 1651 1652 /* check that memory (src_reg + off) is readable, 1653 * the state of dst_reg will be updated by this func 1654 */ 1655 err = check_mem_access(env, insn->src_reg, insn->off, 1656 BPF_SIZE(insn->code), BPF_READ, 1657 insn->dst_reg); 1658 if (err) 1659 return err; 1660 1661 if (BPF_SIZE(insn->code) != BPF_W) { 1662 insn_idx++; 1663 continue; 1664 } 1665 1666 if (insn->imm == 0) { 1667 /* saw a valid insn 1668 * dst_reg = *(u32 *)(src_reg + off) 1669 * use reserved 'imm' field to mark this insn 1670 */ 1671 insn->imm = src_reg_type; 1672 1673 } else if (src_reg_type != insn->imm && 1674 (src_reg_type == PTR_TO_CTX || 1675 insn->imm == PTR_TO_CTX)) { 1676 /* ABuser program is trying to use the same insn 1677 * dst_reg = *(u32*) (src_reg + off) 1678 * with different pointer types: 1679 * src_reg == ctx in one branch and 1680 * src_reg == stack|map in some other branch. 1681 * Reject it. 1682 */ 1683 verbose("same insn cannot be used with different pointers\n"); 1684 return -EINVAL; 1685 } 1686 1687 } else if (class == BPF_STX) { 1688 if (BPF_MODE(insn->code) == BPF_XADD) { 1689 err = check_xadd(env, insn); 1690 if (err) 1691 return err; 1692 insn_idx++; 1693 continue; 1694 } 1695 1696 if (BPF_MODE(insn->code) != BPF_MEM || 1697 insn->imm != 0) { 1698 verbose("BPF_STX uses reserved fields\n"); 1699 return -EINVAL; 1700 } 1701 /* check src1 operand */ 1702 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1703 if (err) 1704 return err; 1705 /* check src2 operand */ 1706 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1707 if (err) 1708 return err; 1709 1710 /* check that memory (dst_reg + off) is writeable */ 1711 err = check_mem_access(env, insn->dst_reg, insn->off, 1712 BPF_SIZE(insn->code), BPF_WRITE, 1713 insn->src_reg); 1714 if (err) 1715 return err; 1716 1717 } else if (class == BPF_ST) { 1718 if (BPF_MODE(insn->code) != BPF_MEM || 1719 insn->src_reg != BPF_REG_0) { 1720 verbose("BPF_ST uses reserved fields\n"); 1721 return -EINVAL; 1722 } 1723 /* check src operand */ 1724 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1725 if (err) 1726 return err; 1727 1728 /* check that memory (dst_reg + off) is writeable */ 1729 err = check_mem_access(env, insn->dst_reg, insn->off, 1730 BPF_SIZE(insn->code), BPF_WRITE, 1731 -1); 1732 if (err) 1733 return err; 1734 1735 } else if (class == BPF_JMP) { 1736 u8 opcode = BPF_OP(insn->code); 1737 1738 if (opcode == BPF_CALL) { 1739 if (BPF_SRC(insn->code) != BPF_K || 1740 insn->off != 0 || 1741 insn->src_reg != BPF_REG_0 || 1742 insn->dst_reg != BPF_REG_0) { 1743 verbose("BPF_CALL uses reserved fields\n"); 1744 return -EINVAL; 1745 } 1746 1747 err = check_call(env, insn->imm); 1748 if (err) 1749 return err; 1750 1751 } else if (opcode == BPF_JA) { 1752 if (BPF_SRC(insn->code) != BPF_K || 1753 insn->imm != 0 || 1754 insn->src_reg != BPF_REG_0 || 1755 insn->dst_reg != BPF_REG_0) { 1756 verbose("BPF_JA uses reserved fields\n"); 1757 return -EINVAL; 1758 } 1759 1760 insn_idx += insn->off + 1; 1761 continue; 1762 1763 } else if (opcode == BPF_EXIT) { 1764 if (BPF_SRC(insn->code) != BPF_K || 1765 insn->imm != 0 || 1766 insn->src_reg != BPF_REG_0 || 1767 insn->dst_reg != BPF_REG_0) { 1768 verbose("BPF_EXIT uses reserved fields\n"); 1769 return -EINVAL; 1770 } 1771 1772 /* eBPF calling convetion is such that R0 is used 1773 * to return the value from eBPF program. 1774 * Make sure that it's readable at this time 1775 * of bpf_exit, which means that program wrote 1776 * something into it earlier 1777 */ 1778 err = check_reg_arg(regs, BPF_REG_0, SRC_OP); 1779 if (err) 1780 return err; 1781 1782process_bpf_exit: 1783 insn_idx = pop_stack(env, &prev_insn_idx); 1784 if (insn_idx < 0) { 1785 break; 1786 } else { 1787 do_print_state = true; 1788 continue; 1789 } 1790 } else { 1791 err = check_cond_jmp_op(env, insn, &insn_idx); 1792 if (err) 1793 return err; 1794 } 1795 } else if (class == BPF_LD) { 1796 u8 mode = BPF_MODE(insn->code); 1797 1798 if (mode == BPF_ABS || mode == BPF_IND) { 1799 err = check_ld_abs(env, insn); 1800 if (err) 1801 return err; 1802 1803 } else if (mode == BPF_IMM) { 1804 err = check_ld_imm(env, insn); 1805 if (err) 1806 return err; 1807 1808 insn_idx++; 1809 } else { 1810 verbose("invalid BPF_LD mode\n"); 1811 return -EINVAL; 1812 } 1813 } else { 1814 verbose("unknown insn class %d\n", class); 1815 return -EINVAL; 1816 } 1817 1818 insn_idx++; 1819 } 1820 1821 return 0; 1822} 1823 1824/* look for pseudo eBPF instructions that access map FDs and 1825 * replace them with actual map pointers 1826 */ 1827static int replace_map_fd_with_map_ptr(struct verifier_env *env) 1828{ 1829 struct bpf_insn *insn = env->prog->insnsi; 1830 int insn_cnt = env->prog->len; 1831 int i, j; 1832 1833 for (i = 0; i < insn_cnt; i++, insn++) { 1834 if (BPF_CLASS(insn->code) == BPF_LDX && 1835 (BPF_MODE(insn->code) != BPF_MEM || 1836 insn->imm != 0)) { 1837 verbose("BPF_LDX uses reserved fields\n"); 1838 return -EINVAL; 1839 } 1840 1841 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) { 1842 struct bpf_map *map; 1843 struct fd f; 1844 1845 if (i == insn_cnt - 1 || insn[1].code != 0 || 1846 insn[1].dst_reg != 0 || insn[1].src_reg != 0 || 1847 insn[1].off != 0) { 1848 verbose("invalid bpf_ld_imm64 insn\n"); 1849 return -EINVAL; 1850 } 1851 1852 if (insn->src_reg == 0) 1853 /* valid generic load 64-bit imm */ 1854 goto next_insn; 1855 1856 if (insn->src_reg != BPF_PSEUDO_MAP_FD) { 1857 verbose("unrecognized bpf_ld_imm64 insn\n"); 1858 return -EINVAL; 1859 } 1860 1861 f = fdget(insn->imm); 1862 1863 map = bpf_map_get(f); 1864 if (IS_ERR(map)) { 1865 verbose("fd %d is not pointing to valid bpf_map\n", 1866 insn->imm); 1867 fdput(f); 1868 return PTR_ERR(map); 1869 } 1870 1871 /* store map pointer inside BPF_LD_IMM64 instruction */ 1872 insn[0].imm = (u32) (unsigned long) map; 1873 insn[1].imm = ((u64) (unsigned long) map) >> 32; 1874 1875 /* check whether we recorded this map already */ 1876 for (j = 0; j < env->used_map_cnt; j++) 1877 if (env->used_maps[j] == map) { 1878 fdput(f); 1879 goto next_insn; 1880 } 1881 1882 if (env->used_map_cnt >= MAX_USED_MAPS) { 1883 fdput(f); 1884 return -E2BIG; 1885 } 1886 1887 /* remember this map */ 1888 env->used_maps[env->used_map_cnt++] = map; 1889 1890 /* hold the map. If the program is rejected by verifier, 1891 * the map will be released by release_maps() or it 1892 * will be used by the valid program until it's unloaded 1893 * and all maps are released in free_bpf_prog_info() 1894 */ 1895 atomic_inc(&map->refcnt); 1896 1897 fdput(f); 1898next_insn: 1899 insn++; 1900 i++; 1901 } 1902 } 1903 1904 /* now all pseudo BPF_LD_IMM64 instructions load valid 1905 * 'struct bpf_map *' into a register instead of user map_fd. 1906 * These pointers will be used later by verifier to validate map access. 1907 */ 1908 return 0; 1909} 1910 1911/* drop refcnt of maps used by the rejected program */ 1912static void release_maps(struct verifier_env *env) 1913{ 1914 int i; 1915 1916 for (i = 0; i < env->used_map_cnt; i++) 1917 bpf_map_put(env->used_maps[i]); 1918} 1919 1920/* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */ 1921static void convert_pseudo_ld_imm64(struct verifier_env *env) 1922{ 1923 struct bpf_insn *insn = env->prog->insnsi; 1924 int insn_cnt = env->prog->len; 1925 int i; 1926 1927 for (i = 0; i < insn_cnt; i++, insn++) 1928 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW)) 1929 insn->src_reg = 0; 1930} 1931 1932static void adjust_branches(struct bpf_prog *prog, int pos, int delta) 1933{ 1934 struct bpf_insn *insn = prog->insnsi; 1935 int insn_cnt = prog->len; 1936 int i; 1937 1938 for (i = 0; i < insn_cnt; i++, insn++) { 1939 if (BPF_CLASS(insn->code) != BPF_JMP || 1940 BPF_OP(insn->code) == BPF_CALL || 1941 BPF_OP(insn->code) == BPF_EXIT) 1942 continue; 1943 1944 /* adjust offset of jmps if necessary */ 1945 if (i < pos && i + insn->off + 1 > pos) 1946 insn->off += delta; 1947 else if (i > pos + delta && i + insn->off + 1 <= pos + delta) 1948 insn->off -= delta; 1949 } 1950} 1951 1952/* convert load instructions that access fields of 'struct __sk_buff' 1953 * into sequence of instructions that access fields of 'struct sk_buff' 1954 */ 1955static int convert_ctx_accesses(struct verifier_env *env) 1956{ 1957 struct bpf_insn *insn = env->prog->insnsi; 1958 int insn_cnt = env->prog->len; 1959 struct bpf_insn insn_buf[16]; 1960 struct bpf_prog *new_prog; 1961 u32 cnt; 1962 int i; 1963 1964 if (!env->prog->aux->ops->convert_ctx_access) 1965 return 0; 1966 1967 for (i = 0; i < insn_cnt; i++, insn++) { 1968 if (insn->code != (BPF_LDX | BPF_MEM | BPF_W)) 1969 continue; 1970 1971 if (insn->imm != PTR_TO_CTX) { 1972 /* clear internal mark */ 1973 insn->imm = 0; 1974 continue; 1975 } 1976 1977 cnt = env->prog->aux->ops-> 1978 convert_ctx_access(insn->dst_reg, insn->src_reg, 1979 insn->off, insn_buf); 1980 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) { 1981 verbose("bpf verifier is misconfigured\n"); 1982 return -EINVAL; 1983 } 1984 1985 if (cnt == 1) { 1986 memcpy(insn, insn_buf, sizeof(*insn)); 1987 continue; 1988 } 1989 1990 /* several new insns need to be inserted. Make room for them */ 1991 insn_cnt += cnt - 1; 1992 new_prog = bpf_prog_realloc(env->prog, 1993 bpf_prog_size(insn_cnt), 1994 GFP_USER); 1995 if (!new_prog) 1996 return -ENOMEM; 1997 1998 new_prog->len = insn_cnt; 1999 2000 memmove(new_prog->insnsi + i + cnt, new_prog->insns + i + 1, 2001 sizeof(*insn) * (insn_cnt - i - cnt)); 2002 2003 /* copy substitute insns in place of load instruction */ 2004 memcpy(new_prog->insnsi + i, insn_buf, sizeof(*insn) * cnt); 2005 2006 /* adjust branches in the whole program */ 2007 adjust_branches(new_prog, i, cnt - 1); 2008 2009 /* keep walking new program and skip insns we just inserted */ 2010 env->prog = new_prog; 2011 insn = new_prog->insnsi + i + cnt - 1; 2012 i += cnt - 1; 2013 } 2014 2015 return 0; 2016} 2017 2018static void free_states(struct verifier_env *env) 2019{ 2020 struct verifier_state_list *sl, *sln; 2021 int i; 2022 2023 if (!env->explored_states) 2024 return; 2025 2026 for (i = 0; i < env->prog->len; i++) { 2027 sl = env->explored_states[i]; 2028 2029 if (sl) 2030 while (sl != STATE_LIST_MARK) { 2031 sln = sl->next; 2032 kfree(sl); 2033 sl = sln; 2034 } 2035 } 2036 2037 kfree(env->explored_states); 2038} 2039 2040int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) 2041{ 2042 char __user *log_ubuf = NULL; 2043 struct verifier_env *env; 2044 int ret = -EINVAL; 2045 2046 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS) 2047 return -E2BIG; 2048 2049 /* 'struct verifier_env' can be global, but since it's not small, 2050 * allocate/free it every time bpf_check() is called 2051 */ 2052 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL); 2053 if (!env) 2054 return -ENOMEM; 2055 2056 env->prog = *prog; 2057 2058 /* grab the mutex to protect few globals used by verifier */ 2059 mutex_lock(&bpf_verifier_lock); 2060 2061 if (attr->log_level || attr->log_buf || attr->log_size) { 2062 /* user requested verbose verifier output 2063 * and supplied buffer to store the verification trace 2064 */ 2065 log_level = attr->log_level; 2066 log_ubuf = (char __user *) (unsigned long) attr->log_buf; 2067 log_size = attr->log_size; 2068 log_len = 0; 2069 2070 ret = -EINVAL; 2071 /* log_* values have to be sane */ 2072 if (log_size < 128 || log_size > UINT_MAX >> 8 || 2073 log_level == 0 || log_ubuf == NULL) 2074 goto free_env; 2075 2076 ret = -ENOMEM; 2077 log_buf = vmalloc(log_size); 2078 if (!log_buf) 2079 goto free_env; 2080 } else { 2081 log_level = 0; 2082 } 2083 2084 ret = replace_map_fd_with_map_ptr(env); 2085 if (ret < 0) 2086 goto skip_full_check; 2087 2088 env->explored_states = kcalloc(env->prog->len, 2089 sizeof(struct verifier_state_list *), 2090 GFP_USER); 2091 ret = -ENOMEM; 2092 if (!env->explored_states) 2093 goto skip_full_check; 2094 2095 ret = check_cfg(env); 2096 if (ret < 0) 2097 goto skip_full_check; 2098 2099 ret = do_check(env); 2100 2101skip_full_check: 2102 while (pop_stack(env, NULL) >= 0); 2103 free_states(env); 2104 2105 if (ret == 0) 2106 /* program is valid, convert *(u32*)(ctx + off) accesses */ 2107 ret = convert_ctx_accesses(env); 2108 2109 if (log_level && log_len >= log_size - 1) { 2110 BUG_ON(log_len >= log_size); 2111 /* verifier log exceeded user supplied buffer */ 2112 ret = -ENOSPC; 2113 /* fall through to return what was recorded */ 2114 } 2115 2116 /* copy verifier log back to user space including trailing zero */ 2117 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) { 2118 ret = -EFAULT; 2119 goto free_log_buf; 2120 } 2121 2122 if (ret == 0 && env->used_map_cnt) { 2123 /* if program passed verifier, update used_maps in bpf_prog_info */ 2124 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt, 2125 sizeof(env->used_maps[0]), 2126 GFP_KERNEL); 2127 2128 if (!env->prog->aux->used_maps) { 2129 ret = -ENOMEM; 2130 goto free_log_buf; 2131 } 2132 2133 memcpy(env->prog->aux->used_maps, env->used_maps, 2134 sizeof(env->used_maps[0]) * env->used_map_cnt); 2135 env->prog->aux->used_map_cnt = env->used_map_cnt; 2136 2137 /* program is valid. Convert pseudo bpf_ld_imm64 into generic 2138 * bpf_ld_imm64 instructions 2139 */ 2140 convert_pseudo_ld_imm64(env); 2141 } 2142 2143free_log_buf: 2144 if (log_level) 2145 vfree(log_buf); 2146free_env: 2147 if (!env->prog->aux->used_maps) 2148 /* if we didn't copy map pointers into bpf_prog_info, release 2149 * them now. Otherwise free_bpf_prog_info() will release them. 2150 */ 2151 release_maps(env); 2152 *prog = env->prog; 2153 kfree(env); 2154 mutex_unlock(&bpf_verifier_lock); 2155 return ret; 2156} 2157