1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com 2 * 3 * This program is free software; you can redistribute it and/or 4 * modify it under the terms of version 2 of the GNU General Public 5 * License as published by the Free Software Foundation. 6 * 7 * This program is distributed in the hope that it will be useful, but 8 * WITHOUT ANY WARRANTY; without even the implied warranty of 9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 10 * General Public License for more details. 11 */ 12 #include <linux/kernel.h> 13 #include <linux/types.h> 14 #include <linux/slab.h> 15 #include <linux/bpf.h> 16 #include <linux/filter.h> 17 #include <net/netlink.h> 18 #include <linux/file.h> 19 #include <linux/vmalloc.h> 20 21 /* bpf_check() is a static code analyzer that walks eBPF program 22 * instruction by instruction and updates register/stack state. 23 * All paths of conditional branches are analyzed until 'bpf_exit' insn. 24 * 25 * The first pass is depth-first-search to check that the program is a DAG. 26 * It rejects the following programs: 27 * - larger than BPF_MAXINSNS insns 28 * - if loop is present (detected via back-edge) 29 * - unreachable insns exist (shouldn't be a forest. program = one function) 30 * - out of bounds or malformed jumps 31 * The second pass is all possible path descent from the 1st insn. 32 * Since it's analyzing all pathes through the program, the length of the 33 * analysis is limited to 32k insn, which may be hit even if total number of 34 * insn is less then 4K, but there are too many branches that change stack/regs. 35 * Number of 'branches to be analyzed' is limited to 1k 36 * 37 * On entry to each instruction, each register has a type, and the instruction 38 * changes the types of the registers depending on instruction semantics. 39 * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is 40 * copied to R1. 41 * 42 * All registers are 64-bit. 43 * R0 - return register 44 * R1-R5 argument passing registers 45 * R6-R9 callee saved registers 46 * R10 - frame pointer read-only 47 * 48 * At the start of BPF program the register R1 contains a pointer to bpf_context 49 * and has type PTR_TO_CTX. 50 * 51 * Verifier tracks arithmetic operations on pointers in case: 52 * BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), 53 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20), 54 * 1st insn copies R10 (which has FRAME_PTR) type into R1 55 * and 2nd arithmetic instruction is pattern matched to recognize 56 * that it wants to construct a pointer to some element within stack. 57 * So after 2nd insn, the register R1 has type PTR_TO_STACK 58 * (and -20 constant is saved for further stack bounds checking). 59 * Meaning that this reg is a pointer to stack plus known immediate constant. 60 * 61 * Most of the time the registers have UNKNOWN_VALUE type, which 62 * means the register has some value, but it's not a valid pointer. 63 * (like pointer plus pointer becomes UNKNOWN_VALUE type) 64 * 65 * When verifier sees load or store instructions the type of base register 66 * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, FRAME_PTR. These are three pointer 67 * types recognized by check_mem_access() function. 68 * 69 * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value' 70 * and the range of [ptr, ptr + map's value_size) is accessible. 71 * 72 * registers used to pass values to function calls are checked against 73 * function argument constraints. 74 * 75 * ARG_PTR_TO_MAP_KEY is one of such argument constraints. 76 * It means that the register type passed to this function must be 77 * PTR_TO_STACK and it will be used inside the function as 78 * 'pointer to map element key' 79 * 80 * For example the argument constraints for bpf_map_lookup_elem(): 81 * .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, 82 * .arg1_type = ARG_CONST_MAP_PTR, 83 * .arg2_type = ARG_PTR_TO_MAP_KEY, 84 * 85 * ret_type says that this function returns 'pointer to map elem value or null' 86 * function expects 1st argument to be a const pointer to 'struct bpf_map' and 87 * 2nd argument should be a pointer to stack, which will be used inside 88 * the helper function as a pointer to map element key. 89 * 90 * On the kernel side the helper function looks like: 91 * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) 92 * { 93 * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1; 94 * void *key = (void *) (unsigned long) r2; 95 * void *value; 96 * 97 * here kernel can access 'key' and 'map' pointers safely, knowing that 98 * [key, key + map->key_size) bytes are valid and were initialized on 99 * the stack of eBPF program. 100 * } 101 * 102 * Corresponding eBPF program may look like: 103 * BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR 104 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK 105 * BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP 106 * BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), 107 * here verifier looks at prototype of map_lookup_elem() and sees: 108 * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok, 109 * Now verifier knows that this map has key of R1->map_ptr->key_size bytes 110 * 111 * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far, 112 * Now verifier checks that [R2, R2 + map's key_size) are within stack limits 113 * and were initialized prior to this call. 114 * If it's ok, then verifier allows this BPF_CALL insn and looks at 115 * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets 116 * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function 117 * returns ether pointer to map value or NULL. 118 * 119 * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off' 120 * insn, the register holding that pointer in the true branch changes state to 121 * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false 122 * branch. See check_cond_jmp_op(). 123 * 124 * After the call R0 is set to return type of the function and registers R1-R5 125 * are set to NOT_INIT to indicate that they are no longer readable. 126 */ 127 128 /* types of values stored in eBPF registers */ 129 enum bpf_reg_type { 130 NOT_INIT = 0, /* nothing was written into register */ 131 UNKNOWN_VALUE, /* reg doesn't contain a valid pointer */ 132 PTR_TO_CTX, /* reg points to bpf_context */ 133 CONST_PTR_TO_MAP, /* reg points to struct bpf_map */ 134 PTR_TO_MAP_VALUE, /* reg points to map element value */ 135 PTR_TO_MAP_VALUE_OR_NULL,/* points to map elem value or NULL */ 136 FRAME_PTR, /* reg == frame_pointer */ 137 PTR_TO_STACK, /* reg == frame_pointer + imm */ 138 CONST_IMM, /* constant integer value */ 139 }; 140 141 struct reg_state { 142 enum bpf_reg_type type; 143 union { 144 /* valid when type == CONST_IMM | PTR_TO_STACK */ 145 int imm; 146 147 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE | 148 * PTR_TO_MAP_VALUE_OR_NULL 149 */ 150 struct bpf_map *map_ptr; 151 }; 152 }; 153 154 enum bpf_stack_slot_type { 155 STACK_INVALID, /* nothing was stored in this stack slot */ 156 STACK_SPILL, /* register spilled into stack */ 157 STACK_MISC /* BPF program wrote some data into this slot */ 158 }; 159 160 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */ 161 162 /* state of the program: 163 * type of all registers and stack info 164 */ 165 struct verifier_state { 166 struct reg_state regs[MAX_BPF_REG]; 167 u8 stack_slot_type[MAX_BPF_STACK]; 168 struct reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE]; 169 }; 170 171 /* linked list of verifier states used to prune search */ 172 struct verifier_state_list { 173 struct verifier_state state; 174 struct verifier_state_list *next; 175 }; 176 177 /* verifier_state + insn_idx are pushed to stack when branch is encountered */ 178 struct verifier_stack_elem { 179 /* verifer state is 'st' 180 * before processing instruction 'insn_idx' 181 * and after processing instruction 'prev_insn_idx' 182 */ 183 struct verifier_state st; 184 int insn_idx; 185 int prev_insn_idx; 186 struct verifier_stack_elem *next; 187 }; 188 189 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */ 190 191 /* single container for all structs 192 * one verifier_env per bpf_check() call 193 */ 194 struct verifier_env { 195 struct bpf_prog *prog; /* eBPF program being verified */ 196 struct verifier_stack_elem *head; /* stack of verifier states to be processed */ 197 int stack_size; /* number of states to be processed */ 198 struct verifier_state cur_state; /* current verifier state */ 199 struct verifier_state_list **explored_states; /* search pruning optimization */ 200 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */ 201 u32 used_map_cnt; /* number of used maps */ 202 bool allow_ptr_leaks; 203 }; 204 205 /* verbose verifier prints what it's seeing 206 * bpf_check() is called under lock, so no race to access these global vars 207 */ 208 static u32 log_level, log_size, log_len; 209 static char *log_buf; 210 211 static DEFINE_MUTEX(bpf_verifier_lock); 212 213 /* log_level controls verbosity level of eBPF verifier. 214 * verbose() is used to dump the verification trace to the log, so the user 215 * can figure out what's wrong with the program 216 */ 217 static __printf(1, 2) void verbose(const char *fmt, ...) 218 { 219 va_list args; 220 221 if (log_level == 0 || log_len >= log_size - 1) 222 return; 223 224 va_start(args, fmt); 225 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args); 226 va_end(args); 227 } 228 229 /* string representation of 'enum bpf_reg_type' */ 230 static const char * const reg_type_str[] = { 231 [NOT_INIT] = "?", 232 [UNKNOWN_VALUE] = "inv", 233 [PTR_TO_CTX] = "ctx", 234 [CONST_PTR_TO_MAP] = "map_ptr", 235 [PTR_TO_MAP_VALUE] = "map_value", 236 [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null", 237 [FRAME_PTR] = "fp", 238 [PTR_TO_STACK] = "fp", 239 [CONST_IMM] = "imm", 240 }; 241 242 static const struct { 243 int map_type; 244 int func_id; 245 } func_limit[] = { 246 {BPF_MAP_TYPE_PROG_ARRAY, BPF_FUNC_tail_call}, 247 {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_read}, 248 {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_output}, 249 {BPF_MAP_TYPE_STACK_TRACE, BPF_FUNC_get_stackid}, 250 }; 251 252 static void print_verifier_state(struct verifier_env *env) 253 { 254 enum bpf_reg_type t; 255 int i; 256 257 for (i = 0; i < MAX_BPF_REG; i++) { 258 t = env->cur_state.regs[i].type; 259 if (t == NOT_INIT) 260 continue; 261 verbose(" R%d=%s", i, reg_type_str[t]); 262 if (t == CONST_IMM || t == PTR_TO_STACK) 263 verbose("%d", env->cur_state.regs[i].imm); 264 else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE || 265 t == PTR_TO_MAP_VALUE_OR_NULL) 266 verbose("(ks=%d,vs=%d)", 267 env->cur_state.regs[i].map_ptr->key_size, 268 env->cur_state.regs[i].map_ptr->value_size); 269 } 270 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 271 if (env->cur_state.stack_slot_type[i] == STACK_SPILL) 272 verbose(" fp%d=%s", -MAX_BPF_STACK + i, 273 reg_type_str[env->cur_state.spilled_regs[i / BPF_REG_SIZE].type]); 274 } 275 verbose("\n"); 276 } 277 278 static const char *const bpf_class_string[] = { 279 [BPF_LD] = "ld", 280 [BPF_LDX] = "ldx", 281 [BPF_ST] = "st", 282 [BPF_STX] = "stx", 283 [BPF_ALU] = "alu", 284 [BPF_JMP] = "jmp", 285 [BPF_RET] = "BUG", 286 [BPF_ALU64] = "alu64", 287 }; 288 289 static const char *const bpf_alu_string[16] = { 290 [BPF_ADD >> 4] = "+=", 291 [BPF_SUB >> 4] = "-=", 292 [BPF_MUL >> 4] = "*=", 293 [BPF_DIV >> 4] = "/=", 294 [BPF_OR >> 4] = "|=", 295 [BPF_AND >> 4] = "&=", 296 [BPF_LSH >> 4] = "<<=", 297 [BPF_RSH >> 4] = ">>=", 298 [BPF_NEG >> 4] = "neg", 299 [BPF_MOD >> 4] = "%=", 300 [BPF_XOR >> 4] = "^=", 301 [BPF_MOV >> 4] = "=", 302 [BPF_ARSH >> 4] = "s>>=", 303 [BPF_END >> 4] = "endian", 304 }; 305 306 static const char *const bpf_ldst_string[] = { 307 [BPF_W >> 3] = "u32", 308 [BPF_H >> 3] = "u16", 309 [BPF_B >> 3] = "u8", 310 [BPF_DW >> 3] = "u64", 311 }; 312 313 static const char *const bpf_jmp_string[16] = { 314 [BPF_JA >> 4] = "jmp", 315 [BPF_JEQ >> 4] = "==", 316 [BPF_JGT >> 4] = ">", 317 [BPF_JGE >> 4] = ">=", 318 [BPF_JSET >> 4] = "&", 319 [BPF_JNE >> 4] = "!=", 320 [BPF_JSGT >> 4] = "s>", 321 [BPF_JSGE >> 4] = "s>=", 322 [BPF_CALL >> 4] = "call", 323 [BPF_EXIT >> 4] = "exit", 324 }; 325 326 static void print_bpf_insn(struct bpf_insn *insn) 327 { 328 u8 class = BPF_CLASS(insn->code); 329 330 if (class == BPF_ALU || class == BPF_ALU64) { 331 if (BPF_SRC(insn->code) == BPF_X) 332 verbose("(%02x) %sr%d %s %sr%d\n", 333 insn->code, class == BPF_ALU ? "(u32) " : "", 334 insn->dst_reg, 335 bpf_alu_string[BPF_OP(insn->code) >> 4], 336 class == BPF_ALU ? "(u32) " : "", 337 insn->src_reg); 338 else 339 verbose("(%02x) %sr%d %s %s%d\n", 340 insn->code, class == BPF_ALU ? "(u32) " : "", 341 insn->dst_reg, 342 bpf_alu_string[BPF_OP(insn->code) >> 4], 343 class == BPF_ALU ? "(u32) " : "", 344 insn->imm); 345 } else if (class == BPF_STX) { 346 if (BPF_MODE(insn->code) == BPF_MEM) 347 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n", 348 insn->code, 349 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 350 insn->dst_reg, 351 insn->off, insn->src_reg); 352 else if (BPF_MODE(insn->code) == BPF_XADD) 353 verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n", 354 insn->code, 355 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 356 insn->dst_reg, insn->off, 357 insn->src_reg); 358 else 359 verbose("BUG_%02x\n", insn->code); 360 } else if (class == BPF_ST) { 361 if (BPF_MODE(insn->code) != BPF_MEM) { 362 verbose("BUG_st_%02x\n", insn->code); 363 return; 364 } 365 verbose("(%02x) *(%s *)(r%d %+d) = %d\n", 366 insn->code, 367 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 368 insn->dst_reg, 369 insn->off, insn->imm); 370 } else if (class == BPF_LDX) { 371 if (BPF_MODE(insn->code) != BPF_MEM) { 372 verbose("BUG_ldx_%02x\n", insn->code); 373 return; 374 } 375 verbose("(%02x) r%d = *(%s *)(r%d %+d)\n", 376 insn->code, insn->dst_reg, 377 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 378 insn->src_reg, insn->off); 379 } else if (class == BPF_LD) { 380 if (BPF_MODE(insn->code) == BPF_ABS) { 381 verbose("(%02x) r0 = *(%s *)skb[%d]\n", 382 insn->code, 383 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 384 insn->imm); 385 } else if (BPF_MODE(insn->code) == BPF_IND) { 386 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n", 387 insn->code, 388 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 389 insn->src_reg, insn->imm); 390 } else if (BPF_MODE(insn->code) == BPF_IMM) { 391 verbose("(%02x) r%d = 0x%x\n", 392 insn->code, insn->dst_reg, insn->imm); 393 } else { 394 verbose("BUG_ld_%02x\n", insn->code); 395 return; 396 } 397 } else if (class == BPF_JMP) { 398 u8 opcode = BPF_OP(insn->code); 399 400 if (opcode == BPF_CALL) { 401 verbose("(%02x) call %d\n", insn->code, insn->imm); 402 } else if (insn->code == (BPF_JMP | BPF_JA)) { 403 verbose("(%02x) goto pc%+d\n", 404 insn->code, insn->off); 405 } else if (insn->code == (BPF_JMP | BPF_EXIT)) { 406 verbose("(%02x) exit\n", insn->code); 407 } else if (BPF_SRC(insn->code) == BPF_X) { 408 verbose("(%02x) if r%d %s r%d goto pc%+d\n", 409 insn->code, insn->dst_reg, 410 bpf_jmp_string[BPF_OP(insn->code) >> 4], 411 insn->src_reg, insn->off); 412 } else { 413 verbose("(%02x) if r%d %s 0x%x goto pc%+d\n", 414 insn->code, insn->dst_reg, 415 bpf_jmp_string[BPF_OP(insn->code) >> 4], 416 insn->imm, insn->off); 417 } 418 } else { 419 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]); 420 } 421 } 422 423 static int pop_stack(struct verifier_env *env, int *prev_insn_idx) 424 { 425 struct verifier_stack_elem *elem; 426 int insn_idx; 427 428 if (env->head == NULL) 429 return -1; 430 431 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state)); 432 insn_idx = env->head->insn_idx; 433 if (prev_insn_idx) 434 *prev_insn_idx = env->head->prev_insn_idx; 435 elem = env->head->next; 436 kfree(env->head); 437 env->head = elem; 438 env->stack_size--; 439 return insn_idx; 440 } 441 442 static struct verifier_state *push_stack(struct verifier_env *env, int insn_idx, 443 int prev_insn_idx) 444 { 445 struct verifier_stack_elem *elem; 446 447 elem = kmalloc(sizeof(struct verifier_stack_elem), GFP_KERNEL); 448 if (!elem) 449 goto err; 450 451 memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state)); 452 elem->insn_idx = insn_idx; 453 elem->prev_insn_idx = prev_insn_idx; 454 elem->next = env->head; 455 env->head = elem; 456 env->stack_size++; 457 if (env->stack_size > 1024) { 458 verbose("BPF program is too complex\n"); 459 goto err; 460 } 461 return &elem->st; 462 err: 463 /* pop all elements and return */ 464 while (pop_stack(env, NULL) >= 0); 465 return NULL; 466 } 467 468 #define CALLER_SAVED_REGS 6 469 static const int caller_saved[CALLER_SAVED_REGS] = { 470 BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5 471 }; 472 473 static void init_reg_state(struct reg_state *regs) 474 { 475 int i; 476 477 for (i = 0; i < MAX_BPF_REG; i++) { 478 regs[i].type = NOT_INIT; 479 regs[i].imm = 0; 480 regs[i].map_ptr = NULL; 481 } 482 483 /* frame pointer */ 484 regs[BPF_REG_FP].type = FRAME_PTR; 485 486 /* 1st arg to a function */ 487 regs[BPF_REG_1].type = PTR_TO_CTX; 488 } 489 490 static void mark_reg_unknown_value(struct reg_state *regs, u32 regno) 491 { 492 BUG_ON(regno >= MAX_BPF_REG); 493 regs[regno].type = UNKNOWN_VALUE; 494 regs[regno].imm = 0; 495 regs[regno].map_ptr = NULL; 496 } 497 498 enum reg_arg_type { 499 SRC_OP, /* register is used as source operand */ 500 DST_OP, /* register is used as destination operand */ 501 DST_OP_NO_MARK /* same as above, check only, don't mark */ 502 }; 503 504 static int check_reg_arg(struct reg_state *regs, u32 regno, 505 enum reg_arg_type t) 506 { 507 if (regno >= MAX_BPF_REG) { 508 verbose("R%d is invalid\n", regno); 509 return -EINVAL; 510 } 511 512 if (t == SRC_OP) { 513 /* check whether register used as source operand can be read */ 514 if (regs[regno].type == NOT_INIT) { 515 verbose("R%d !read_ok\n", regno); 516 return -EACCES; 517 } 518 } else { 519 /* check whether register used as dest operand can be written to */ 520 if (regno == BPF_REG_FP) { 521 verbose("frame pointer is read only\n"); 522 return -EACCES; 523 } 524 if (t == DST_OP) 525 mark_reg_unknown_value(regs, regno); 526 } 527 return 0; 528 } 529 530 static int bpf_size_to_bytes(int bpf_size) 531 { 532 if (bpf_size == BPF_W) 533 return 4; 534 else if (bpf_size == BPF_H) 535 return 2; 536 else if (bpf_size == BPF_B) 537 return 1; 538 else if (bpf_size == BPF_DW) 539 return 8; 540 else 541 return -EINVAL; 542 } 543 544 static bool is_spillable_regtype(enum bpf_reg_type type) 545 { 546 switch (type) { 547 case PTR_TO_MAP_VALUE: 548 case PTR_TO_MAP_VALUE_OR_NULL: 549 case PTR_TO_STACK: 550 case PTR_TO_CTX: 551 case FRAME_PTR: 552 case CONST_PTR_TO_MAP: 553 return true; 554 default: 555 return false; 556 } 557 } 558 559 /* check_stack_read/write functions track spill/fill of registers, 560 * stack boundary and alignment are checked in check_mem_access() 561 */ 562 static int check_stack_write(struct verifier_state *state, int off, int size, 563 int value_regno) 564 { 565 int i; 566 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0, 567 * so it's aligned access and [off, off + size) are within stack limits 568 */ 569 570 if (value_regno >= 0 && 571 is_spillable_regtype(state->regs[value_regno].type)) { 572 573 /* register containing pointer is being spilled into stack */ 574 if (size != BPF_REG_SIZE) { 575 verbose("invalid size of register spill\n"); 576 return -EACCES; 577 } 578 579 /* save register state */ 580 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = 581 state->regs[value_regno]; 582 583 for (i = 0; i < BPF_REG_SIZE; i++) 584 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL; 585 } else { 586 /* regular write of data into stack */ 587 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = 588 (struct reg_state) {}; 589 590 for (i = 0; i < size; i++) 591 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC; 592 } 593 return 0; 594 } 595 596 static int check_stack_read(struct verifier_state *state, int off, int size, 597 int value_regno) 598 { 599 u8 *slot_type; 600 int i; 601 602 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off]; 603 604 if (slot_type[0] == STACK_SPILL) { 605 if (size != BPF_REG_SIZE) { 606 verbose("invalid size of register spill\n"); 607 return -EACCES; 608 } 609 for (i = 1; i < BPF_REG_SIZE; i++) { 610 if (slot_type[i] != STACK_SPILL) { 611 verbose("corrupted spill memory\n"); 612 return -EACCES; 613 } 614 } 615 616 if (value_regno >= 0) 617 /* restore register state from stack */ 618 state->regs[value_regno] = 619 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE]; 620 return 0; 621 } else { 622 for (i = 0; i < size; i++) { 623 if (slot_type[i] != STACK_MISC) { 624 verbose("invalid read from stack off %d+%d size %d\n", 625 off, i, size); 626 return -EACCES; 627 } 628 } 629 if (value_regno >= 0) 630 /* have read misc data from the stack */ 631 mark_reg_unknown_value(state->regs, value_regno); 632 return 0; 633 } 634 } 635 636 /* check read/write into map element returned by bpf_map_lookup_elem() */ 637 static int check_map_access(struct verifier_env *env, u32 regno, int off, 638 int size) 639 { 640 struct bpf_map *map = env->cur_state.regs[regno].map_ptr; 641 642 if (off < 0 || off + size > map->value_size) { 643 verbose("invalid access to map value, value_size=%d off=%d size=%d\n", 644 map->value_size, off, size); 645 return -EACCES; 646 } 647 return 0; 648 } 649 650 /* check access to 'struct bpf_context' fields */ 651 static int check_ctx_access(struct verifier_env *env, int off, int size, 652 enum bpf_access_type t) 653 { 654 if (env->prog->aux->ops->is_valid_access && 655 env->prog->aux->ops->is_valid_access(off, size, t)) 656 return 0; 657 658 verbose("invalid bpf_context access off=%d size=%d\n", off, size); 659 return -EACCES; 660 } 661 662 static bool is_pointer_value(struct verifier_env *env, int regno) 663 { 664 if (env->allow_ptr_leaks) 665 return false; 666 667 switch (env->cur_state.regs[regno].type) { 668 case UNKNOWN_VALUE: 669 case CONST_IMM: 670 return false; 671 default: 672 return true; 673 } 674 } 675 676 /* check whether memory at (regno + off) is accessible for t = (read | write) 677 * if t==write, value_regno is a register which value is stored into memory 678 * if t==read, value_regno is a register which will receive the value from memory 679 * if t==write && value_regno==-1, some unknown value is stored into memory 680 * if t==read && value_regno==-1, don't care what we read from memory 681 */ 682 static int check_mem_access(struct verifier_env *env, u32 regno, int off, 683 int bpf_size, enum bpf_access_type t, 684 int value_regno) 685 { 686 struct verifier_state *state = &env->cur_state; 687 int size, err = 0; 688 689 if (state->regs[regno].type == PTR_TO_STACK) 690 off += state->regs[regno].imm; 691 692 size = bpf_size_to_bytes(bpf_size); 693 if (size < 0) 694 return size; 695 696 if (off % size != 0) { 697 verbose("misaligned access off %d size %d\n", off, size); 698 return -EACCES; 699 } 700 701 if (state->regs[regno].type == PTR_TO_MAP_VALUE) { 702 if (t == BPF_WRITE && value_regno >= 0 && 703 is_pointer_value(env, value_regno)) { 704 verbose("R%d leaks addr into map\n", value_regno); 705 return -EACCES; 706 } 707 err = check_map_access(env, regno, off, size); 708 if (!err && t == BPF_READ && value_regno >= 0) 709 mark_reg_unknown_value(state->regs, value_regno); 710 711 } else if (state->regs[regno].type == PTR_TO_CTX) { 712 if (t == BPF_WRITE && value_regno >= 0 && 713 is_pointer_value(env, value_regno)) { 714 verbose("R%d leaks addr into ctx\n", value_regno); 715 return -EACCES; 716 } 717 err = check_ctx_access(env, off, size, t); 718 if (!err && t == BPF_READ && value_regno >= 0) 719 mark_reg_unknown_value(state->regs, value_regno); 720 721 } else if (state->regs[regno].type == FRAME_PTR || 722 state->regs[regno].type == PTR_TO_STACK) { 723 if (off >= 0 || off < -MAX_BPF_STACK) { 724 verbose("invalid stack off=%d size=%d\n", off, size); 725 return -EACCES; 726 } 727 if (t == BPF_WRITE) { 728 if (!env->allow_ptr_leaks && 729 state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL && 730 size != BPF_REG_SIZE) { 731 verbose("attempt to corrupt spilled pointer on stack\n"); 732 return -EACCES; 733 } 734 err = check_stack_write(state, off, size, value_regno); 735 } else { 736 err = check_stack_read(state, off, size, value_regno); 737 } 738 } else { 739 verbose("R%d invalid mem access '%s'\n", 740 regno, reg_type_str[state->regs[regno].type]); 741 return -EACCES; 742 } 743 return err; 744 } 745 746 static int check_xadd(struct verifier_env *env, struct bpf_insn *insn) 747 { 748 struct reg_state *regs = env->cur_state.regs; 749 int err; 750 751 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) || 752 insn->imm != 0) { 753 verbose("BPF_XADD uses reserved fields\n"); 754 return -EINVAL; 755 } 756 757 /* check src1 operand */ 758 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 759 if (err) 760 return err; 761 762 /* check src2 operand */ 763 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 764 if (err) 765 return err; 766 767 /* check whether atomic_add can read the memory */ 768 err = check_mem_access(env, insn->dst_reg, insn->off, 769 BPF_SIZE(insn->code), BPF_READ, -1); 770 if (err) 771 return err; 772 773 /* check whether atomic_add can write into the same memory */ 774 return check_mem_access(env, insn->dst_reg, insn->off, 775 BPF_SIZE(insn->code), BPF_WRITE, -1); 776 } 777 778 /* when register 'regno' is passed into function that will read 'access_size' 779 * bytes from that pointer, make sure that it's within stack boundary 780 * and all elements of stack are initialized 781 */ 782 static int check_stack_boundary(struct verifier_env *env, int regno, 783 int access_size, bool zero_size_allowed) 784 { 785 struct verifier_state *state = &env->cur_state; 786 struct reg_state *regs = state->regs; 787 int off, i; 788 789 if (regs[regno].type != PTR_TO_STACK) { 790 if (zero_size_allowed && access_size == 0 && 791 regs[regno].type == CONST_IMM && 792 regs[regno].imm == 0) 793 return 0; 794 795 verbose("R%d type=%s expected=%s\n", regno, 796 reg_type_str[regs[regno].type], 797 reg_type_str[PTR_TO_STACK]); 798 return -EACCES; 799 } 800 801 off = regs[regno].imm; 802 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 || 803 access_size <= 0) { 804 verbose("invalid stack type R%d off=%d access_size=%d\n", 805 regno, off, access_size); 806 return -EACCES; 807 } 808 809 for (i = 0; i < access_size; i++) { 810 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) { 811 verbose("invalid indirect read from stack off %d+%d size %d\n", 812 off, i, access_size); 813 return -EACCES; 814 } 815 } 816 return 0; 817 } 818 819 static int check_func_arg(struct verifier_env *env, u32 regno, 820 enum bpf_arg_type arg_type, struct bpf_map **mapp) 821 { 822 struct reg_state *reg = env->cur_state.regs + regno; 823 enum bpf_reg_type expected_type; 824 int err = 0; 825 826 if (arg_type == ARG_DONTCARE) 827 return 0; 828 829 if (reg->type == NOT_INIT) { 830 verbose("R%d !read_ok\n", regno); 831 return -EACCES; 832 } 833 834 if (arg_type == ARG_ANYTHING) { 835 if (is_pointer_value(env, regno)) { 836 verbose("R%d leaks addr into helper function\n", regno); 837 return -EACCES; 838 } 839 return 0; 840 } 841 842 if (arg_type == ARG_PTR_TO_MAP_KEY || 843 arg_type == ARG_PTR_TO_MAP_VALUE) { 844 expected_type = PTR_TO_STACK; 845 } else if (arg_type == ARG_CONST_STACK_SIZE || 846 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) { 847 expected_type = CONST_IMM; 848 } else if (arg_type == ARG_CONST_MAP_PTR) { 849 expected_type = CONST_PTR_TO_MAP; 850 } else if (arg_type == ARG_PTR_TO_CTX) { 851 expected_type = PTR_TO_CTX; 852 } else if (arg_type == ARG_PTR_TO_STACK) { 853 expected_type = PTR_TO_STACK; 854 /* One exception here. In case function allows for NULL to be 855 * passed in as argument, it's a CONST_IMM type. Final test 856 * happens during stack boundary checking. 857 */ 858 if (reg->type == CONST_IMM && reg->imm == 0) 859 expected_type = CONST_IMM; 860 } else { 861 verbose("unsupported arg_type %d\n", arg_type); 862 return -EFAULT; 863 } 864 865 if (reg->type != expected_type) { 866 verbose("R%d type=%s expected=%s\n", regno, 867 reg_type_str[reg->type], reg_type_str[expected_type]); 868 return -EACCES; 869 } 870 871 if (arg_type == ARG_CONST_MAP_PTR) { 872 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */ 873 *mapp = reg->map_ptr; 874 875 } else if (arg_type == ARG_PTR_TO_MAP_KEY) { 876 /* bpf_map_xxx(..., map_ptr, ..., key) call: 877 * check that [key, key + map->key_size) are within 878 * stack limits and initialized 879 */ 880 if (!*mapp) { 881 /* in function declaration map_ptr must come before 882 * map_key, so that it's verified and known before 883 * we have to check map_key here. Otherwise it means 884 * that kernel subsystem misconfigured verifier 885 */ 886 verbose("invalid map_ptr to access map->key\n"); 887 return -EACCES; 888 } 889 err = check_stack_boundary(env, regno, (*mapp)->key_size, 890 false); 891 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) { 892 /* bpf_map_xxx(..., map_ptr, ..., value) call: 893 * check [value, value + map->value_size) validity 894 */ 895 if (!*mapp) { 896 /* kernel subsystem misconfigured verifier */ 897 verbose("invalid map_ptr to access map->value\n"); 898 return -EACCES; 899 } 900 err = check_stack_boundary(env, regno, (*mapp)->value_size, 901 false); 902 } else if (arg_type == ARG_CONST_STACK_SIZE || 903 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) { 904 bool zero_size_allowed = (arg_type == ARG_CONST_STACK_SIZE_OR_ZERO); 905 906 /* bpf_xxx(..., buf, len) call will access 'len' bytes 907 * from stack pointer 'buf'. Check it 908 * note: regno == len, regno - 1 == buf 909 */ 910 if (regno == 0) { 911 /* kernel subsystem misconfigured verifier */ 912 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n"); 913 return -EACCES; 914 } 915 err = check_stack_boundary(env, regno - 1, reg->imm, 916 zero_size_allowed); 917 } 918 919 return err; 920 } 921 922 static int check_map_func_compatibility(struct bpf_map *map, int func_id) 923 { 924 bool bool_map, bool_func; 925 int i; 926 927 if (!map) 928 return 0; 929 930 for (i = 0; i < ARRAY_SIZE(func_limit); i++) { 931 bool_map = (map->map_type == func_limit[i].map_type); 932 bool_func = (func_id == func_limit[i].func_id); 933 /* only when map & func pair match it can continue. 934 * don't allow any other map type to be passed into 935 * the special func; 936 */ 937 if (bool_func && bool_map != bool_func) { 938 verbose("cannot pass map_type %d into func %d\n", 939 map->map_type, func_id); 940 return -EINVAL; 941 } 942 } 943 944 return 0; 945 } 946 947 static int check_call(struct verifier_env *env, int func_id) 948 { 949 struct verifier_state *state = &env->cur_state; 950 const struct bpf_func_proto *fn = NULL; 951 struct reg_state *regs = state->regs; 952 struct bpf_map *map = NULL; 953 struct reg_state *reg; 954 int i, err; 955 956 /* find function prototype */ 957 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) { 958 verbose("invalid func %d\n", func_id); 959 return -EINVAL; 960 } 961 962 if (env->prog->aux->ops->get_func_proto) 963 fn = env->prog->aux->ops->get_func_proto(func_id); 964 965 if (!fn) { 966 verbose("unknown func %d\n", func_id); 967 return -EINVAL; 968 } 969 970 /* eBPF programs must be GPL compatible to use GPL-ed functions */ 971 if (!env->prog->gpl_compatible && fn->gpl_only) { 972 verbose("cannot call GPL only function from proprietary program\n"); 973 return -EINVAL; 974 } 975 976 /* check args */ 977 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &map); 978 if (err) 979 return err; 980 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &map); 981 if (err) 982 return err; 983 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &map); 984 if (err) 985 return err; 986 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &map); 987 if (err) 988 return err; 989 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &map); 990 if (err) 991 return err; 992 993 /* reset caller saved regs */ 994 for (i = 0; i < CALLER_SAVED_REGS; i++) { 995 reg = regs + caller_saved[i]; 996 reg->type = NOT_INIT; 997 reg->imm = 0; 998 } 999 1000 /* update return register */ 1001 if (fn->ret_type == RET_INTEGER) { 1002 regs[BPF_REG_0].type = UNKNOWN_VALUE; 1003 } else if (fn->ret_type == RET_VOID) { 1004 regs[BPF_REG_0].type = NOT_INIT; 1005 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) { 1006 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL; 1007 /* remember map_ptr, so that check_map_access() 1008 * can check 'value_size' boundary of memory access 1009 * to map element returned from bpf_map_lookup_elem() 1010 */ 1011 if (map == NULL) { 1012 verbose("kernel subsystem misconfigured verifier\n"); 1013 return -EINVAL; 1014 } 1015 regs[BPF_REG_0].map_ptr = map; 1016 } else { 1017 verbose("unknown return type %d of func %d\n", 1018 fn->ret_type, func_id); 1019 return -EINVAL; 1020 } 1021 1022 err = check_map_func_compatibility(map, func_id); 1023 if (err) 1024 return err; 1025 1026 return 0; 1027 } 1028 1029 /* check validity of 32-bit and 64-bit arithmetic operations */ 1030 static int check_alu_op(struct verifier_env *env, struct bpf_insn *insn) 1031 { 1032 struct reg_state *regs = env->cur_state.regs; 1033 u8 opcode = BPF_OP(insn->code); 1034 int err; 1035 1036 if (opcode == BPF_END || opcode == BPF_NEG) { 1037 if (opcode == BPF_NEG) { 1038 if (BPF_SRC(insn->code) != 0 || 1039 insn->src_reg != BPF_REG_0 || 1040 insn->off != 0 || insn->imm != 0) { 1041 verbose("BPF_NEG uses reserved fields\n"); 1042 return -EINVAL; 1043 } 1044 } else { 1045 if (insn->src_reg != BPF_REG_0 || insn->off != 0 || 1046 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) { 1047 verbose("BPF_END uses reserved fields\n"); 1048 return -EINVAL; 1049 } 1050 } 1051 1052 /* check src operand */ 1053 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1054 if (err) 1055 return err; 1056 1057 if (is_pointer_value(env, insn->dst_reg)) { 1058 verbose("R%d pointer arithmetic prohibited\n", 1059 insn->dst_reg); 1060 return -EACCES; 1061 } 1062 1063 /* check dest operand */ 1064 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1065 if (err) 1066 return err; 1067 1068 } else if (opcode == BPF_MOV) { 1069 1070 if (BPF_SRC(insn->code) == BPF_X) { 1071 if (insn->imm != 0 || insn->off != 0) { 1072 verbose("BPF_MOV uses reserved fields\n"); 1073 return -EINVAL; 1074 } 1075 1076 /* check src operand */ 1077 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1078 if (err) 1079 return err; 1080 } else { 1081 if (insn->src_reg != BPF_REG_0 || insn->off != 0) { 1082 verbose("BPF_MOV uses reserved fields\n"); 1083 return -EINVAL; 1084 } 1085 } 1086 1087 /* check dest operand */ 1088 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1089 if (err) 1090 return err; 1091 1092 if (BPF_SRC(insn->code) == BPF_X) { 1093 if (BPF_CLASS(insn->code) == BPF_ALU64) { 1094 /* case: R1 = R2 1095 * copy register state to dest reg 1096 */ 1097 regs[insn->dst_reg] = regs[insn->src_reg]; 1098 } else { 1099 if (is_pointer_value(env, insn->src_reg)) { 1100 verbose("R%d partial copy of pointer\n", 1101 insn->src_reg); 1102 return -EACCES; 1103 } 1104 regs[insn->dst_reg].type = UNKNOWN_VALUE; 1105 regs[insn->dst_reg].map_ptr = NULL; 1106 } 1107 } else { 1108 /* case: R = imm 1109 * remember the value we stored into this reg 1110 */ 1111 regs[insn->dst_reg].type = CONST_IMM; 1112 regs[insn->dst_reg].imm = insn->imm; 1113 } 1114 1115 } else if (opcode > BPF_END) { 1116 verbose("invalid BPF_ALU opcode %x\n", opcode); 1117 return -EINVAL; 1118 1119 } else { /* all other ALU ops: and, sub, xor, add, ... */ 1120 1121 bool stack_relative = false; 1122 1123 if (BPF_SRC(insn->code) == BPF_X) { 1124 if (insn->imm != 0 || insn->off != 0) { 1125 verbose("BPF_ALU uses reserved fields\n"); 1126 return -EINVAL; 1127 } 1128 /* check src1 operand */ 1129 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1130 if (err) 1131 return err; 1132 } else { 1133 if (insn->src_reg != BPF_REG_0 || insn->off != 0) { 1134 verbose("BPF_ALU uses reserved fields\n"); 1135 return -EINVAL; 1136 } 1137 } 1138 1139 /* check src2 operand */ 1140 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1141 if (err) 1142 return err; 1143 1144 if ((opcode == BPF_MOD || opcode == BPF_DIV) && 1145 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) { 1146 verbose("div by zero\n"); 1147 return -EINVAL; 1148 } 1149 1150 if ((opcode == BPF_LSH || opcode == BPF_RSH || 1151 opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) { 1152 int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32; 1153 1154 if (insn->imm < 0 || insn->imm >= size) { 1155 verbose("invalid shift %d\n", insn->imm); 1156 return -EINVAL; 1157 } 1158 } 1159 1160 /* pattern match 'bpf_add Rx, imm' instruction */ 1161 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 && 1162 regs[insn->dst_reg].type == FRAME_PTR && 1163 BPF_SRC(insn->code) == BPF_K) { 1164 stack_relative = true; 1165 } else if (is_pointer_value(env, insn->dst_reg)) { 1166 verbose("R%d pointer arithmetic prohibited\n", 1167 insn->dst_reg); 1168 return -EACCES; 1169 } else if (BPF_SRC(insn->code) == BPF_X && 1170 is_pointer_value(env, insn->src_reg)) { 1171 verbose("R%d pointer arithmetic prohibited\n", 1172 insn->src_reg); 1173 return -EACCES; 1174 } 1175 1176 /* check dest operand */ 1177 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1178 if (err) 1179 return err; 1180 1181 if (stack_relative) { 1182 regs[insn->dst_reg].type = PTR_TO_STACK; 1183 regs[insn->dst_reg].imm = insn->imm; 1184 } 1185 } 1186 1187 return 0; 1188 } 1189 1190 static int check_cond_jmp_op(struct verifier_env *env, 1191 struct bpf_insn *insn, int *insn_idx) 1192 { 1193 struct reg_state *regs = env->cur_state.regs; 1194 struct verifier_state *other_branch; 1195 u8 opcode = BPF_OP(insn->code); 1196 int err; 1197 1198 if (opcode > BPF_EXIT) { 1199 verbose("invalid BPF_JMP opcode %x\n", opcode); 1200 return -EINVAL; 1201 } 1202 1203 if (BPF_SRC(insn->code) == BPF_X) { 1204 if (insn->imm != 0) { 1205 verbose("BPF_JMP uses reserved fields\n"); 1206 return -EINVAL; 1207 } 1208 1209 /* check src1 operand */ 1210 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1211 if (err) 1212 return err; 1213 1214 if (is_pointer_value(env, insn->src_reg)) { 1215 verbose("R%d pointer comparison prohibited\n", 1216 insn->src_reg); 1217 return -EACCES; 1218 } 1219 } else { 1220 if (insn->src_reg != BPF_REG_0) { 1221 verbose("BPF_JMP uses reserved fields\n"); 1222 return -EINVAL; 1223 } 1224 } 1225 1226 /* check src2 operand */ 1227 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1228 if (err) 1229 return err; 1230 1231 /* detect if R == 0 where R was initialized to zero earlier */ 1232 if (BPF_SRC(insn->code) == BPF_K && 1233 (opcode == BPF_JEQ || opcode == BPF_JNE) && 1234 regs[insn->dst_reg].type == CONST_IMM && 1235 regs[insn->dst_reg].imm == insn->imm) { 1236 if (opcode == BPF_JEQ) { 1237 /* if (imm == imm) goto pc+off; 1238 * only follow the goto, ignore fall-through 1239 */ 1240 *insn_idx += insn->off; 1241 return 0; 1242 } else { 1243 /* if (imm != imm) goto pc+off; 1244 * only follow fall-through branch, since 1245 * that's where the program will go 1246 */ 1247 return 0; 1248 } 1249 } 1250 1251 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx); 1252 if (!other_branch) 1253 return -EFAULT; 1254 1255 /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */ 1256 if (BPF_SRC(insn->code) == BPF_K && 1257 insn->imm == 0 && (opcode == BPF_JEQ || 1258 opcode == BPF_JNE) && 1259 regs[insn->dst_reg].type == PTR_TO_MAP_VALUE_OR_NULL) { 1260 if (opcode == BPF_JEQ) { 1261 /* next fallthrough insn can access memory via 1262 * this register 1263 */ 1264 regs[insn->dst_reg].type = PTR_TO_MAP_VALUE; 1265 /* branch targer cannot access it, since reg == 0 */ 1266 other_branch->regs[insn->dst_reg].type = CONST_IMM; 1267 other_branch->regs[insn->dst_reg].imm = 0; 1268 } else { 1269 other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE; 1270 regs[insn->dst_reg].type = CONST_IMM; 1271 regs[insn->dst_reg].imm = 0; 1272 } 1273 } else if (is_pointer_value(env, insn->dst_reg)) { 1274 verbose("R%d pointer comparison prohibited\n", insn->dst_reg); 1275 return -EACCES; 1276 } else if (BPF_SRC(insn->code) == BPF_K && 1277 (opcode == BPF_JEQ || opcode == BPF_JNE)) { 1278 1279 if (opcode == BPF_JEQ) { 1280 /* detect if (R == imm) goto 1281 * and in the target state recognize that R = imm 1282 */ 1283 other_branch->regs[insn->dst_reg].type = CONST_IMM; 1284 other_branch->regs[insn->dst_reg].imm = insn->imm; 1285 } else { 1286 /* detect if (R != imm) goto 1287 * and in the fall-through state recognize that R = imm 1288 */ 1289 regs[insn->dst_reg].type = CONST_IMM; 1290 regs[insn->dst_reg].imm = insn->imm; 1291 } 1292 } 1293 if (log_level) 1294 print_verifier_state(env); 1295 return 0; 1296 } 1297 1298 /* return the map pointer stored inside BPF_LD_IMM64 instruction */ 1299 static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn) 1300 { 1301 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32; 1302 1303 return (struct bpf_map *) (unsigned long) imm64; 1304 } 1305 1306 /* verify BPF_LD_IMM64 instruction */ 1307 static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn) 1308 { 1309 struct reg_state *regs = env->cur_state.regs; 1310 int err; 1311 1312 if (BPF_SIZE(insn->code) != BPF_DW) { 1313 verbose("invalid BPF_LD_IMM insn\n"); 1314 return -EINVAL; 1315 } 1316 if (insn->off != 0) { 1317 verbose("BPF_LD_IMM64 uses reserved fields\n"); 1318 return -EINVAL; 1319 } 1320 1321 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1322 if (err) 1323 return err; 1324 1325 if (insn->src_reg == 0) 1326 /* generic move 64-bit immediate into a register */ 1327 return 0; 1328 1329 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */ 1330 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD); 1331 1332 regs[insn->dst_reg].type = CONST_PTR_TO_MAP; 1333 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn); 1334 return 0; 1335 } 1336 1337 static bool may_access_skb(enum bpf_prog_type type) 1338 { 1339 switch (type) { 1340 case BPF_PROG_TYPE_SOCKET_FILTER: 1341 case BPF_PROG_TYPE_SCHED_CLS: 1342 case BPF_PROG_TYPE_SCHED_ACT: 1343 return true; 1344 default: 1345 return false; 1346 } 1347 } 1348 1349 /* verify safety of LD_ABS|LD_IND instructions: 1350 * - they can only appear in the programs where ctx == skb 1351 * - since they are wrappers of function calls, they scratch R1-R5 registers, 1352 * preserve R6-R9, and store return value into R0 1353 * 1354 * Implicit input: 1355 * ctx == skb == R6 == CTX 1356 * 1357 * Explicit input: 1358 * SRC == any register 1359 * IMM == 32-bit immediate 1360 * 1361 * Output: 1362 * R0 - 8/16/32-bit skb data converted to cpu endianness 1363 */ 1364 static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn) 1365 { 1366 struct reg_state *regs = env->cur_state.regs; 1367 u8 mode = BPF_MODE(insn->code); 1368 struct reg_state *reg; 1369 int i, err; 1370 1371 if (!may_access_skb(env->prog->type)) { 1372 verbose("BPF_LD_ABS|IND instructions not allowed for this program type\n"); 1373 return -EINVAL; 1374 } 1375 1376 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 || 1377 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) { 1378 verbose("BPF_LD_ABS uses reserved fields\n"); 1379 return -EINVAL; 1380 } 1381 1382 /* check whether implicit source operand (register R6) is readable */ 1383 err = check_reg_arg(regs, BPF_REG_6, SRC_OP); 1384 if (err) 1385 return err; 1386 1387 if (regs[BPF_REG_6].type != PTR_TO_CTX) { 1388 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n"); 1389 return -EINVAL; 1390 } 1391 1392 if (mode == BPF_IND) { 1393 /* check explicit source operand */ 1394 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1395 if (err) 1396 return err; 1397 } 1398 1399 /* reset caller saved regs to unreadable */ 1400 for (i = 0; i < CALLER_SAVED_REGS; i++) { 1401 reg = regs + caller_saved[i]; 1402 reg->type = NOT_INIT; 1403 reg->imm = 0; 1404 } 1405 1406 /* mark destination R0 register as readable, since it contains 1407 * the value fetched from the packet 1408 */ 1409 regs[BPF_REG_0].type = UNKNOWN_VALUE; 1410 return 0; 1411 } 1412 1413 /* non-recursive DFS pseudo code 1414 * 1 procedure DFS-iterative(G,v): 1415 * 2 label v as discovered 1416 * 3 let S be a stack 1417 * 4 S.push(v) 1418 * 5 while S is not empty 1419 * 6 t <- S.pop() 1420 * 7 if t is what we're looking for: 1421 * 8 return t 1422 * 9 for all edges e in G.adjacentEdges(t) do 1423 * 10 if edge e is already labelled 1424 * 11 continue with the next edge 1425 * 12 w <- G.adjacentVertex(t,e) 1426 * 13 if vertex w is not discovered and not explored 1427 * 14 label e as tree-edge 1428 * 15 label w as discovered 1429 * 16 S.push(w) 1430 * 17 continue at 5 1431 * 18 else if vertex w is discovered 1432 * 19 label e as back-edge 1433 * 20 else 1434 * 21 // vertex w is explored 1435 * 22 label e as forward- or cross-edge 1436 * 23 label t as explored 1437 * 24 S.pop() 1438 * 1439 * convention: 1440 * 0x10 - discovered 1441 * 0x11 - discovered and fall-through edge labelled 1442 * 0x12 - discovered and fall-through and branch edges labelled 1443 * 0x20 - explored 1444 */ 1445 1446 enum { 1447 DISCOVERED = 0x10, 1448 EXPLORED = 0x20, 1449 FALLTHROUGH = 1, 1450 BRANCH = 2, 1451 }; 1452 1453 #define STATE_LIST_MARK ((struct verifier_state_list *) -1L) 1454 1455 static int *insn_stack; /* stack of insns to process */ 1456 static int cur_stack; /* current stack index */ 1457 static int *insn_state; 1458 1459 /* t, w, e - match pseudo-code above: 1460 * t - index of current instruction 1461 * w - next instruction 1462 * e - edge 1463 */ 1464 static int push_insn(int t, int w, int e, struct verifier_env *env) 1465 { 1466 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH)) 1467 return 0; 1468 1469 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH)) 1470 return 0; 1471 1472 if (w < 0 || w >= env->prog->len) { 1473 verbose("jump out of range from insn %d to %d\n", t, w); 1474 return -EINVAL; 1475 } 1476 1477 if (e == BRANCH) 1478 /* mark branch target for state pruning */ 1479 env->explored_states[w] = STATE_LIST_MARK; 1480 1481 if (insn_state[w] == 0) { 1482 /* tree-edge */ 1483 insn_state[t] = DISCOVERED | e; 1484 insn_state[w] = DISCOVERED; 1485 if (cur_stack >= env->prog->len) 1486 return -E2BIG; 1487 insn_stack[cur_stack++] = w; 1488 return 1; 1489 } else if ((insn_state[w] & 0xF0) == DISCOVERED) { 1490 verbose("back-edge from insn %d to %d\n", t, w); 1491 return -EINVAL; 1492 } else if (insn_state[w] == EXPLORED) { 1493 /* forward- or cross-edge */ 1494 insn_state[t] = DISCOVERED | e; 1495 } else { 1496 verbose("insn state internal bug\n"); 1497 return -EFAULT; 1498 } 1499 return 0; 1500 } 1501 1502 /* non-recursive depth-first-search to detect loops in BPF program 1503 * loop == back-edge in directed graph 1504 */ 1505 static int check_cfg(struct verifier_env *env) 1506 { 1507 struct bpf_insn *insns = env->prog->insnsi; 1508 int insn_cnt = env->prog->len; 1509 int ret = 0; 1510 int i, t; 1511 1512 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 1513 if (!insn_state) 1514 return -ENOMEM; 1515 1516 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 1517 if (!insn_stack) { 1518 kfree(insn_state); 1519 return -ENOMEM; 1520 } 1521 1522 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */ 1523 insn_stack[0] = 0; /* 0 is the first instruction */ 1524 cur_stack = 1; 1525 1526 peek_stack: 1527 if (cur_stack == 0) 1528 goto check_state; 1529 t = insn_stack[cur_stack - 1]; 1530 1531 if (BPF_CLASS(insns[t].code) == BPF_JMP) { 1532 u8 opcode = BPF_OP(insns[t].code); 1533 1534 if (opcode == BPF_EXIT) { 1535 goto mark_explored; 1536 } else if (opcode == BPF_CALL) { 1537 ret = push_insn(t, t + 1, FALLTHROUGH, env); 1538 if (ret == 1) 1539 goto peek_stack; 1540 else if (ret < 0) 1541 goto err_free; 1542 } else if (opcode == BPF_JA) { 1543 if (BPF_SRC(insns[t].code) != BPF_K) { 1544 ret = -EINVAL; 1545 goto err_free; 1546 } 1547 /* unconditional jump with single edge */ 1548 ret = push_insn(t, t + insns[t].off + 1, 1549 FALLTHROUGH, env); 1550 if (ret == 1) 1551 goto peek_stack; 1552 else if (ret < 0) 1553 goto err_free; 1554 /* tell verifier to check for equivalent states 1555 * after every call and jump 1556 */ 1557 if (t + 1 < insn_cnt) 1558 env->explored_states[t + 1] = STATE_LIST_MARK; 1559 } else { 1560 /* conditional jump with two edges */ 1561 ret = push_insn(t, t + 1, FALLTHROUGH, env); 1562 if (ret == 1) 1563 goto peek_stack; 1564 else if (ret < 0) 1565 goto err_free; 1566 1567 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env); 1568 if (ret == 1) 1569 goto peek_stack; 1570 else if (ret < 0) 1571 goto err_free; 1572 } 1573 } else { 1574 /* all other non-branch instructions with single 1575 * fall-through edge 1576 */ 1577 ret = push_insn(t, t + 1, FALLTHROUGH, env); 1578 if (ret == 1) 1579 goto peek_stack; 1580 else if (ret < 0) 1581 goto err_free; 1582 } 1583 1584 mark_explored: 1585 insn_state[t] = EXPLORED; 1586 if (cur_stack-- <= 0) { 1587 verbose("pop stack internal bug\n"); 1588 ret = -EFAULT; 1589 goto err_free; 1590 } 1591 goto peek_stack; 1592 1593 check_state: 1594 for (i = 0; i < insn_cnt; i++) { 1595 if (insn_state[i] != EXPLORED) { 1596 verbose("unreachable insn %d\n", i); 1597 ret = -EINVAL; 1598 goto err_free; 1599 } 1600 } 1601 ret = 0; /* cfg looks good */ 1602 1603 err_free: 1604 kfree(insn_state); 1605 kfree(insn_stack); 1606 return ret; 1607 } 1608 1609 /* compare two verifier states 1610 * 1611 * all states stored in state_list are known to be valid, since 1612 * verifier reached 'bpf_exit' instruction through them 1613 * 1614 * this function is called when verifier exploring different branches of 1615 * execution popped from the state stack. If it sees an old state that has 1616 * more strict register state and more strict stack state then this execution 1617 * branch doesn't need to be explored further, since verifier already 1618 * concluded that more strict state leads to valid finish. 1619 * 1620 * Therefore two states are equivalent if register state is more conservative 1621 * and explored stack state is more conservative than the current one. 1622 * Example: 1623 * explored current 1624 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC) 1625 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC) 1626 * 1627 * In other words if current stack state (one being explored) has more 1628 * valid slots than old one that already passed validation, it means 1629 * the verifier can stop exploring and conclude that current state is valid too 1630 * 1631 * Similarly with registers. If explored state has register type as invalid 1632 * whereas register type in current state is meaningful, it means that 1633 * the current state will reach 'bpf_exit' instruction safely 1634 */ 1635 static bool states_equal(struct verifier_state *old, struct verifier_state *cur) 1636 { 1637 int i; 1638 1639 for (i = 0; i < MAX_BPF_REG; i++) { 1640 if (memcmp(&old->regs[i], &cur->regs[i], 1641 sizeof(old->regs[0])) != 0) { 1642 if (old->regs[i].type == NOT_INIT || 1643 (old->regs[i].type == UNKNOWN_VALUE && 1644 cur->regs[i].type != NOT_INIT)) 1645 continue; 1646 return false; 1647 } 1648 } 1649 1650 for (i = 0; i < MAX_BPF_STACK; i++) { 1651 if (old->stack_slot_type[i] == STACK_INVALID) 1652 continue; 1653 if (old->stack_slot_type[i] != cur->stack_slot_type[i]) 1654 /* Ex: old explored (safe) state has STACK_SPILL in 1655 * this stack slot, but current has has STACK_MISC -> 1656 * this verifier states are not equivalent, 1657 * return false to continue verification of this path 1658 */ 1659 return false; 1660 if (i % BPF_REG_SIZE) 1661 continue; 1662 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE], 1663 &cur->spilled_regs[i / BPF_REG_SIZE], 1664 sizeof(old->spilled_regs[0]))) 1665 /* when explored and current stack slot types are 1666 * the same, check that stored pointers types 1667 * are the same as well. 1668 * Ex: explored safe path could have stored 1669 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8} 1670 * but current path has stored: 1671 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16} 1672 * such verifier states are not equivalent. 1673 * return false to continue verification of this path 1674 */ 1675 return false; 1676 else 1677 continue; 1678 } 1679 return true; 1680 } 1681 1682 static int is_state_visited(struct verifier_env *env, int insn_idx) 1683 { 1684 struct verifier_state_list *new_sl; 1685 struct verifier_state_list *sl; 1686 1687 sl = env->explored_states[insn_idx]; 1688 if (!sl) 1689 /* this 'insn_idx' instruction wasn't marked, so we will not 1690 * be doing state search here 1691 */ 1692 return 0; 1693 1694 while (sl != STATE_LIST_MARK) { 1695 if (states_equal(&sl->state, &env->cur_state)) 1696 /* reached equivalent register/stack state, 1697 * prune the search 1698 */ 1699 return 1; 1700 sl = sl->next; 1701 } 1702 1703 /* there were no equivalent states, remember current one. 1704 * technically the current state is not proven to be safe yet, 1705 * but it will either reach bpf_exit (which means it's safe) or 1706 * it will be rejected. Since there are no loops, we won't be 1707 * seeing this 'insn_idx' instruction again on the way to bpf_exit 1708 */ 1709 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER); 1710 if (!new_sl) 1711 return -ENOMEM; 1712 1713 /* add new state to the head of linked list */ 1714 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state)); 1715 new_sl->next = env->explored_states[insn_idx]; 1716 env->explored_states[insn_idx] = new_sl; 1717 return 0; 1718 } 1719 1720 static int do_check(struct verifier_env *env) 1721 { 1722 struct verifier_state *state = &env->cur_state; 1723 struct bpf_insn *insns = env->prog->insnsi; 1724 struct reg_state *regs = state->regs; 1725 int insn_cnt = env->prog->len; 1726 int insn_idx, prev_insn_idx = 0; 1727 int insn_processed = 0; 1728 bool do_print_state = false; 1729 1730 init_reg_state(regs); 1731 insn_idx = 0; 1732 for (;;) { 1733 struct bpf_insn *insn; 1734 u8 class; 1735 int err; 1736 1737 if (insn_idx >= insn_cnt) { 1738 verbose("invalid insn idx %d insn_cnt %d\n", 1739 insn_idx, insn_cnt); 1740 return -EFAULT; 1741 } 1742 1743 insn = &insns[insn_idx]; 1744 class = BPF_CLASS(insn->code); 1745 1746 if (++insn_processed > 32768) { 1747 verbose("BPF program is too large. Proccessed %d insn\n", 1748 insn_processed); 1749 return -E2BIG; 1750 } 1751 1752 err = is_state_visited(env, insn_idx); 1753 if (err < 0) 1754 return err; 1755 if (err == 1) { 1756 /* found equivalent state, can prune the search */ 1757 if (log_level) { 1758 if (do_print_state) 1759 verbose("\nfrom %d to %d: safe\n", 1760 prev_insn_idx, insn_idx); 1761 else 1762 verbose("%d: safe\n", insn_idx); 1763 } 1764 goto process_bpf_exit; 1765 } 1766 1767 if (log_level && do_print_state) { 1768 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx); 1769 print_verifier_state(env); 1770 do_print_state = false; 1771 } 1772 1773 if (log_level) { 1774 verbose("%d: ", insn_idx); 1775 print_bpf_insn(insn); 1776 } 1777 1778 if (class == BPF_ALU || class == BPF_ALU64) { 1779 err = check_alu_op(env, insn); 1780 if (err) 1781 return err; 1782 1783 } else if (class == BPF_LDX) { 1784 enum bpf_reg_type src_reg_type; 1785 1786 /* check for reserved fields is already done */ 1787 1788 /* check src operand */ 1789 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1790 if (err) 1791 return err; 1792 1793 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); 1794 if (err) 1795 return err; 1796 1797 src_reg_type = regs[insn->src_reg].type; 1798 1799 /* check that memory (src_reg + off) is readable, 1800 * the state of dst_reg will be updated by this func 1801 */ 1802 err = check_mem_access(env, insn->src_reg, insn->off, 1803 BPF_SIZE(insn->code), BPF_READ, 1804 insn->dst_reg); 1805 if (err) 1806 return err; 1807 1808 if (BPF_SIZE(insn->code) != BPF_W) { 1809 insn_idx++; 1810 continue; 1811 } 1812 1813 if (insn->imm == 0) { 1814 /* saw a valid insn 1815 * dst_reg = *(u32 *)(src_reg + off) 1816 * use reserved 'imm' field to mark this insn 1817 */ 1818 insn->imm = src_reg_type; 1819 1820 } else if (src_reg_type != insn->imm && 1821 (src_reg_type == PTR_TO_CTX || 1822 insn->imm == PTR_TO_CTX)) { 1823 /* ABuser program is trying to use the same insn 1824 * dst_reg = *(u32*) (src_reg + off) 1825 * with different pointer types: 1826 * src_reg == ctx in one branch and 1827 * src_reg == stack|map in some other branch. 1828 * Reject it. 1829 */ 1830 verbose("same insn cannot be used with different pointers\n"); 1831 return -EINVAL; 1832 } 1833 1834 } else if (class == BPF_STX) { 1835 enum bpf_reg_type dst_reg_type; 1836 1837 if (BPF_MODE(insn->code) == BPF_XADD) { 1838 err = check_xadd(env, insn); 1839 if (err) 1840 return err; 1841 insn_idx++; 1842 continue; 1843 } 1844 1845 /* check src1 operand */ 1846 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1847 if (err) 1848 return err; 1849 /* check src2 operand */ 1850 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1851 if (err) 1852 return err; 1853 1854 dst_reg_type = regs[insn->dst_reg].type; 1855 1856 /* check that memory (dst_reg + off) is writeable */ 1857 err = check_mem_access(env, insn->dst_reg, insn->off, 1858 BPF_SIZE(insn->code), BPF_WRITE, 1859 insn->src_reg); 1860 if (err) 1861 return err; 1862 1863 if (insn->imm == 0) { 1864 insn->imm = dst_reg_type; 1865 } else if (dst_reg_type != insn->imm && 1866 (dst_reg_type == PTR_TO_CTX || 1867 insn->imm == PTR_TO_CTX)) { 1868 verbose("same insn cannot be used with different pointers\n"); 1869 return -EINVAL; 1870 } 1871 1872 } else if (class == BPF_ST) { 1873 if (BPF_MODE(insn->code) != BPF_MEM || 1874 insn->src_reg != BPF_REG_0) { 1875 verbose("BPF_ST uses reserved fields\n"); 1876 return -EINVAL; 1877 } 1878 /* check src operand */ 1879 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1880 if (err) 1881 return err; 1882 1883 /* check that memory (dst_reg + off) is writeable */ 1884 err = check_mem_access(env, insn->dst_reg, insn->off, 1885 BPF_SIZE(insn->code), BPF_WRITE, 1886 -1); 1887 if (err) 1888 return err; 1889 1890 } else if (class == BPF_JMP) { 1891 u8 opcode = BPF_OP(insn->code); 1892 1893 if (opcode == BPF_CALL) { 1894 if (BPF_SRC(insn->code) != BPF_K || 1895 insn->off != 0 || 1896 insn->src_reg != BPF_REG_0 || 1897 insn->dst_reg != BPF_REG_0) { 1898 verbose("BPF_CALL uses reserved fields\n"); 1899 return -EINVAL; 1900 } 1901 1902 err = check_call(env, insn->imm); 1903 if (err) 1904 return err; 1905 1906 } else if (opcode == BPF_JA) { 1907 if (BPF_SRC(insn->code) != BPF_K || 1908 insn->imm != 0 || 1909 insn->src_reg != BPF_REG_0 || 1910 insn->dst_reg != BPF_REG_0) { 1911 verbose("BPF_JA uses reserved fields\n"); 1912 return -EINVAL; 1913 } 1914 1915 insn_idx += insn->off + 1; 1916 continue; 1917 1918 } else if (opcode == BPF_EXIT) { 1919 if (BPF_SRC(insn->code) != BPF_K || 1920 insn->imm != 0 || 1921 insn->src_reg != BPF_REG_0 || 1922 insn->dst_reg != BPF_REG_0) { 1923 verbose("BPF_EXIT uses reserved fields\n"); 1924 return -EINVAL; 1925 } 1926 1927 /* eBPF calling convetion is such that R0 is used 1928 * to return the value from eBPF program. 1929 * Make sure that it's readable at this time 1930 * of bpf_exit, which means that program wrote 1931 * something into it earlier 1932 */ 1933 err = check_reg_arg(regs, BPF_REG_0, SRC_OP); 1934 if (err) 1935 return err; 1936 1937 if (is_pointer_value(env, BPF_REG_0)) { 1938 verbose("R0 leaks addr as return value\n"); 1939 return -EACCES; 1940 } 1941 1942 process_bpf_exit: 1943 insn_idx = pop_stack(env, &prev_insn_idx); 1944 if (insn_idx < 0) { 1945 break; 1946 } else { 1947 do_print_state = true; 1948 continue; 1949 } 1950 } else { 1951 err = check_cond_jmp_op(env, insn, &insn_idx); 1952 if (err) 1953 return err; 1954 } 1955 } else if (class == BPF_LD) { 1956 u8 mode = BPF_MODE(insn->code); 1957 1958 if (mode == BPF_ABS || mode == BPF_IND) { 1959 err = check_ld_abs(env, insn); 1960 if (err) 1961 return err; 1962 1963 } else if (mode == BPF_IMM) { 1964 err = check_ld_imm(env, insn); 1965 if (err) 1966 return err; 1967 1968 insn_idx++; 1969 } else { 1970 verbose("invalid BPF_LD mode\n"); 1971 return -EINVAL; 1972 } 1973 } else { 1974 verbose("unknown insn class %d\n", class); 1975 return -EINVAL; 1976 } 1977 1978 insn_idx++; 1979 } 1980 1981 return 0; 1982 } 1983 1984 /* look for pseudo eBPF instructions that access map FDs and 1985 * replace them with actual map pointers 1986 */ 1987 static int replace_map_fd_with_map_ptr(struct verifier_env *env) 1988 { 1989 struct bpf_insn *insn = env->prog->insnsi; 1990 int insn_cnt = env->prog->len; 1991 int i, j; 1992 1993 for (i = 0; i < insn_cnt; i++, insn++) { 1994 if (BPF_CLASS(insn->code) == BPF_LDX && 1995 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) { 1996 verbose("BPF_LDX uses reserved fields\n"); 1997 return -EINVAL; 1998 } 1999 2000 if (BPF_CLASS(insn->code) == BPF_STX && 2001 ((BPF_MODE(insn->code) != BPF_MEM && 2002 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) { 2003 verbose("BPF_STX uses reserved fields\n"); 2004 return -EINVAL; 2005 } 2006 2007 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) { 2008 struct bpf_map *map; 2009 struct fd f; 2010 2011 if (i == insn_cnt - 1 || insn[1].code != 0 || 2012 insn[1].dst_reg != 0 || insn[1].src_reg != 0 || 2013 insn[1].off != 0) { 2014 verbose("invalid bpf_ld_imm64 insn\n"); 2015 return -EINVAL; 2016 } 2017 2018 if (insn->src_reg == 0) 2019 /* valid generic load 64-bit imm */ 2020 goto next_insn; 2021 2022 if (insn->src_reg != BPF_PSEUDO_MAP_FD) { 2023 verbose("unrecognized bpf_ld_imm64 insn\n"); 2024 return -EINVAL; 2025 } 2026 2027 f = fdget(insn->imm); 2028 map = __bpf_map_get(f); 2029 if (IS_ERR(map)) { 2030 verbose("fd %d is not pointing to valid bpf_map\n", 2031 insn->imm); 2032 fdput(f); 2033 return PTR_ERR(map); 2034 } 2035 2036 /* store map pointer inside BPF_LD_IMM64 instruction */ 2037 insn[0].imm = (u32) (unsigned long) map; 2038 insn[1].imm = ((u64) (unsigned long) map) >> 32; 2039 2040 /* check whether we recorded this map already */ 2041 for (j = 0; j < env->used_map_cnt; j++) 2042 if (env->used_maps[j] == map) { 2043 fdput(f); 2044 goto next_insn; 2045 } 2046 2047 if (env->used_map_cnt >= MAX_USED_MAPS) { 2048 fdput(f); 2049 return -E2BIG; 2050 } 2051 2052 /* remember this map */ 2053 env->used_maps[env->used_map_cnt++] = map; 2054 2055 /* hold the map. If the program is rejected by verifier, 2056 * the map will be released by release_maps() or it 2057 * will be used by the valid program until it's unloaded 2058 * and all maps are released in free_bpf_prog_info() 2059 */ 2060 bpf_map_inc(map, false); 2061 fdput(f); 2062 next_insn: 2063 insn++; 2064 i++; 2065 } 2066 } 2067 2068 /* now all pseudo BPF_LD_IMM64 instructions load valid 2069 * 'struct bpf_map *' into a register instead of user map_fd. 2070 * These pointers will be used later by verifier to validate map access. 2071 */ 2072 return 0; 2073 } 2074 2075 /* drop refcnt of maps used by the rejected program */ 2076 static void release_maps(struct verifier_env *env) 2077 { 2078 int i; 2079 2080 for (i = 0; i < env->used_map_cnt; i++) 2081 bpf_map_put(env->used_maps[i]); 2082 } 2083 2084 /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */ 2085 static void convert_pseudo_ld_imm64(struct verifier_env *env) 2086 { 2087 struct bpf_insn *insn = env->prog->insnsi; 2088 int insn_cnt = env->prog->len; 2089 int i; 2090 2091 for (i = 0; i < insn_cnt; i++, insn++) 2092 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW)) 2093 insn->src_reg = 0; 2094 } 2095 2096 static void adjust_branches(struct bpf_prog *prog, int pos, int delta) 2097 { 2098 struct bpf_insn *insn = prog->insnsi; 2099 int insn_cnt = prog->len; 2100 int i; 2101 2102 for (i = 0; i < insn_cnt; i++, insn++) { 2103 if (BPF_CLASS(insn->code) != BPF_JMP || 2104 BPF_OP(insn->code) == BPF_CALL || 2105 BPF_OP(insn->code) == BPF_EXIT) 2106 continue; 2107 2108 /* adjust offset of jmps if necessary */ 2109 if (i < pos && i + insn->off + 1 > pos) 2110 insn->off += delta; 2111 else if (i > pos + delta && i + insn->off + 1 <= pos + delta) 2112 insn->off -= delta; 2113 } 2114 } 2115 2116 /* convert load instructions that access fields of 'struct __sk_buff' 2117 * into sequence of instructions that access fields of 'struct sk_buff' 2118 */ 2119 static int convert_ctx_accesses(struct verifier_env *env) 2120 { 2121 struct bpf_insn *insn = env->prog->insnsi; 2122 int insn_cnt = env->prog->len; 2123 struct bpf_insn insn_buf[16]; 2124 struct bpf_prog *new_prog; 2125 u32 cnt; 2126 int i; 2127 enum bpf_access_type type; 2128 2129 if (!env->prog->aux->ops->convert_ctx_access) 2130 return 0; 2131 2132 for (i = 0; i < insn_cnt; i++, insn++) { 2133 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W)) 2134 type = BPF_READ; 2135 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W)) 2136 type = BPF_WRITE; 2137 else 2138 continue; 2139 2140 if (insn->imm != PTR_TO_CTX) { 2141 /* clear internal mark */ 2142 insn->imm = 0; 2143 continue; 2144 } 2145 2146 cnt = env->prog->aux->ops-> 2147 convert_ctx_access(type, insn->dst_reg, insn->src_reg, 2148 insn->off, insn_buf, env->prog); 2149 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) { 2150 verbose("bpf verifier is misconfigured\n"); 2151 return -EINVAL; 2152 } 2153 2154 if (cnt == 1) { 2155 memcpy(insn, insn_buf, sizeof(*insn)); 2156 continue; 2157 } 2158 2159 /* several new insns need to be inserted. Make room for them */ 2160 insn_cnt += cnt - 1; 2161 new_prog = bpf_prog_realloc(env->prog, 2162 bpf_prog_size(insn_cnt), 2163 GFP_USER); 2164 if (!new_prog) 2165 return -ENOMEM; 2166 2167 new_prog->len = insn_cnt; 2168 2169 memmove(new_prog->insnsi + i + cnt, new_prog->insns + i + 1, 2170 sizeof(*insn) * (insn_cnt - i - cnt)); 2171 2172 /* copy substitute insns in place of load instruction */ 2173 memcpy(new_prog->insnsi + i, insn_buf, sizeof(*insn) * cnt); 2174 2175 /* adjust branches in the whole program */ 2176 adjust_branches(new_prog, i, cnt - 1); 2177 2178 /* keep walking new program and skip insns we just inserted */ 2179 env->prog = new_prog; 2180 insn = new_prog->insnsi + i + cnt - 1; 2181 i += cnt - 1; 2182 } 2183 2184 return 0; 2185 } 2186 2187 static void free_states(struct verifier_env *env) 2188 { 2189 struct verifier_state_list *sl, *sln; 2190 int i; 2191 2192 if (!env->explored_states) 2193 return; 2194 2195 for (i = 0; i < env->prog->len; i++) { 2196 sl = env->explored_states[i]; 2197 2198 if (sl) 2199 while (sl != STATE_LIST_MARK) { 2200 sln = sl->next; 2201 kfree(sl); 2202 sl = sln; 2203 } 2204 } 2205 2206 kfree(env->explored_states); 2207 } 2208 2209 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) 2210 { 2211 char __user *log_ubuf = NULL; 2212 struct verifier_env *env; 2213 int ret = -EINVAL; 2214 2215 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS) 2216 return -E2BIG; 2217 2218 /* 'struct verifier_env' can be global, but since it's not small, 2219 * allocate/free it every time bpf_check() is called 2220 */ 2221 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL); 2222 if (!env) 2223 return -ENOMEM; 2224 2225 env->prog = *prog; 2226 2227 /* grab the mutex to protect few globals used by verifier */ 2228 mutex_lock(&bpf_verifier_lock); 2229 2230 if (attr->log_level || attr->log_buf || attr->log_size) { 2231 /* user requested verbose verifier output 2232 * and supplied buffer to store the verification trace 2233 */ 2234 log_level = attr->log_level; 2235 log_ubuf = (char __user *) (unsigned long) attr->log_buf; 2236 log_size = attr->log_size; 2237 log_len = 0; 2238 2239 ret = -EINVAL; 2240 /* log_* values have to be sane */ 2241 if (log_size < 128 || log_size > UINT_MAX >> 8 || 2242 log_level == 0 || log_ubuf == NULL) 2243 goto free_env; 2244 2245 ret = -ENOMEM; 2246 log_buf = vmalloc(log_size); 2247 if (!log_buf) 2248 goto free_env; 2249 } else { 2250 log_level = 0; 2251 } 2252 2253 ret = replace_map_fd_with_map_ptr(env); 2254 if (ret < 0) 2255 goto skip_full_check; 2256 2257 env->explored_states = kcalloc(env->prog->len, 2258 sizeof(struct verifier_state_list *), 2259 GFP_USER); 2260 ret = -ENOMEM; 2261 if (!env->explored_states) 2262 goto skip_full_check; 2263 2264 ret = check_cfg(env); 2265 if (ret < 0) 2266 goto skip_full_check; 2267 2268 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); 2269 2270 ret = do_check(env); 2271 2272 skip_full_check: 2273 while (pop_stack(env, NULL) >= 0); 2274 free_states(env); 2275 2276 if (ret == 0) 2277 /* program is valid, convert *(u32*)(ctx + off) accesses */ 2278 ret = convert_ctx_accesses(env); 2279 2280 if (log_level && log_len >= log_size - 1) { 2281 BUG_ON(log_len >= log_size); 2282 /* verifier log exceeded user supplied buffer */ 2283 ret = -ENOSPC; 2284 /* fall through to return what was recorded */ 2285 } 2286 2287 /* copy verifier log back to user space including trailing zero */ 2288 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) { 2289 ret = -EFAULT; 2290 goto free_log_buf; 2291 } 2292 2293 if (ret == 0 && env->used_map_cnt) { 2294 /* if program passed verifier, update used_maps in bpf_prog_info */ 2295 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt, 2296 sizeof(env->used_maps[0]), 2297 GFP_KERNEL); 2298 2299 if (!env->prog->aux->used_maps) { 2300 ret = -ENOMEM; 2301 goto free_log_buf; 2302 } 2303 2304 memcpy(env->prog->aux->used_maps, env->used_maps, 2305 sizeof(env->used_maps[0]) * env->used_map_cnt); 2306 env->prog->aux->used_map_cnt = env->used_map_cnt; 2307 2308 /* program is valid. Convert pseudo bpf_ld_imm64 into generic 2309 * bpf_ld_imm64 instructions 2310 */ 2311 convert_pseudo_ld_imm64(env); 2312 } 2313 2314 free_log_buf: 2315 if (log_level) 2316 vfree(log_buf); 2317 free_env: 2318 if (!env->prog->aux->used_maps) 2319 /* if we didn't copy map pointers into bpf_prog_info, release 2320 * them now. Otherwise free_bpf_prog_info() will release them. 2321 */ 2322 release_maps(env); 2323 *prog = env->prog; 2324 kfree(env); 2325 mutex_unlock(&bpf_verifier_lock); 2326 return ret; 2327 } 2328