1/* SPDX-License-Identifier: GPL-2.0-only */ 2/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com 3 */ 4#ifndef _LINUX_BPF_VERIFIER_H 5#define _LINUX_BPF_VERIFIER_H 1 6 7#include <linux/bpf.h> /* for enum bpf_reg_type */ 8#include <linux/filter.h> /* for MAX_BPF_STACK */ 9#include <linux/tnum.h> 10 11/* Maximum variable offset umax_value permitted when resolving memory accesses. 12 * In practice this is far bigger than any realistic pointer offset; this limit 13 * ensures that umax_value + (int)off + (int)size cannot overflow a u64. 14 */ 15#define BPF_MAX_VAR_OFF (1 << 29) 16/* Maximum variable size permitted for ARG_CONST_SIZE[_OR_ZERO]. This ensures 17 * that converting umax_value to int cannot overflow. 18 */ 19#define BPF_MAX_VAR_SIZ (1 << 29) 20 21/* Liveness marks, used for registers and spilled-regs (in stack slots). 22 * Read marks propagate upwards until they find a write mark; they record that 23 * "one of this state's descendants read this reg" (and therefore the reg is 24 * relevant for states_equal() checks). 25 * Write marks collect downwards and do not propagate; they record that "the 26 * straight-line code that reached this state (from its parent) wrote this reg" 27 * (and therefore that reads propagated from this state or its descendants 28 * should not propagate to its parent). 29 * A state with a write mark can receive read marks; it just won't propagate 30 * them to its parent, since the write mark is a property, not of the state, 31 * but of the link between it and its parent. See mark_reg_read() and 32 * mark_stack_slot_read() in kernel/bpf/verifier.c. 33 */ 34enum bpf_reg_liveness { 35 REG_LIVE_NONE = 0, /* reg hasn't been read or written this branch */ 36 REG_LIVE_READ32 = 0x1, /* reg was read, so we're sensitive to initial value */ 37 REG_LIVE_READ64 = 0x2, /* likewise, but full 64-bit content matters */ 38 REG_LIVE_READ = REG_LIVE_READ32 | REG_LIVE_READ64, 39 REG_LIVE_WRITTEN = 0x4, /* reg was written first, screening off later reads */ 40 REG_LIVE_DONE = 0x8, /* liveness won't be updating this register anymore */ 41}; 42 43struct bpf_reg_state { 44 /* Ordering of fields matters. See states_equal() */ 45 enum bpf_reg_type type; 46 union { 47 /* valid when type == PTR_TO_PACKET */ 48 u16 range; 49 50 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE | 51 * PTR_TO_MAP_VALUE_OR_NULL 52 */ 53 struct bpf_map *map_ptr; 54 55 /* Max size from any of the above. */ 56 unsigned long raw; 57 }; 58 /* Fixed part of pointer offset, pointer types only */ 59 s32 off; 60 /* For PTR_TO_PACKET, used to find other pointers with the same variable 61 * offset, so they can share range knowledge. 62 * For PTR_TO_MAP_VALUE_OR_NULL this is used to share which map value we 63 * came from, when one is tested for != NULL. 64 * For PTR_TO_SOCKET this is used to share which pointers retain the 65 * same reference to the socket, to determine proper reference freeing. 66 */ 67 u32 id; 68 /* PTR_TO_SOCKET and PTR_TO_TCP_SOCK could be a ptr returned 69 * from a pointer-cast helper, bpf_sk_fullsock() and 70 * bpf_tcp_sock(). 71 * 72 * Consider the following where "sk" is a reference counted 73 * pointer returned from "sk = bpf_sk_lookup_tcp();": 74 * 75 * 1: sk = bpf_sk_lookup_tcp(); 76 * 2: if (!sk) { return 0; } 77 * 3: fullsock = bpf_sk_fullsock(sk); 78 * 4: if (!fullsock) { bpf_sk_release(sk); return 0; } 79 * 5: tp = bpf_tcp_sock(fullsock); 80 * 6: if (!tp) { bpf_sk_release(sk); return 0; } 81 * 7: bpf_sk_release(sk); 82 * 8: snd_cwnd = tp->snd_cwnd; // verifier will complain 83 * 84 * After bpf_sk_release(sk) at line 7, both "fullsock" ptr and 85 * "tp" ptr should be invalidated also. In order to do that, 86 * the reg holding "fullsock" and "sk" need to remember 87 * the original refcounted ptr id (i.e. sk_reg->id) in ref_obj_id 88 * such that the verifier can reset all regs which have 89 * ref_obj_id matching the sk_reg->id. 90 * 91 * sk_reg->ref_obj_id is set to sk_reg->id at line 1. 92 * sk_reg->id will stay as NULL-marking purpose only. 93 * After NULL-marking is done, sk_reg->id can be reset to 0. 94 * 95 * After "fullsock = bpf_sk_fullsock(sk);" at line 3, 96 * fullsock_reg->ref_obj_id is set to sk_reg->ref_obj_id. 97 * 98 * After "tp = bpf_tcp_sock(fullsock);" at line 5, 99 * tp_reg->ref_obj_id is set to fullsock_reg->ref_obj_id 100 * which is the same as sk_reg->ref_obj_id. 101 * 102 * From the verifier perspective, if sk, fullsock and tp 103 * are not NULL, they are the same ptr with different 104 * reg->type. In particular, bpf_sk_release(tp) is also 105 * allowed and has the same effect as bpf_sk_release(sk). 106 */ 107 u32 ref_obj_id; 108 /* For scalar types (SCALAR_VALUE), this represents our knowledge of 109 * the actual value. 110 * For pointer types, this represents the variable part of the offset 111 * from the pointed-to object, and is shared with all bpf_reg_states 112 * with the same id as us. 113 */ 114 struct tnum var_off; 115 /* Used to determine if any memory access using this register will 116 * result in a bad access. 117 * These refer to the same value as var_off, not necessarily the actual 118 * contents of the register. 119 */ 120 s64 smin_value; /* minimum possible (s64)value */ 121 s64 smax_value; /* maximum possible (s64)value */ 122 u64 umin_value; /* minimum possible (u64)value */ 123 u64 umax_value; /* maximum possible (u64)value */ 124 /* parentage chain for liveness checking */ 125 struct bpf_reg_state *parent; 126 /* Inside the callee two registers can be both PTR_TO_STACK like 127 * R1=fp-8 and R2=fp-8, but one of them points to this function stack 128 * while another to the caller's stack. To differentiate them 'frameno' 129 * is used which is an index in bpf_verifier_state->frame[] array 130 * pointing to bpf_func_state. 131 */ 132 u32 frameno; 133 /* Tracks subreg definition. The stored value is the insn_idx of the 134 * writing insn. This is safe because subreg_def is used before any insn 135 * patching which only happens after main verification finished. 136 */ 137 s32 subreg_def; 138 enum bpf_reg_liveness live; 139 /* if (!precise && SCALAR_VALUE) min/max/tnum don't affect safety */ 140 bool precise; 141}; 142 143enum bpf_stack_slot_type { 144 STACK_INVALID, /* nothing was stored in this stack slot */ 145 STACK_SPILL, /* register spilled into stack */ 146 STACK_MISC, /* BPF program wrote some data into this slot */ 147 STACK_ZERO, /* BPF program wrote constant zero */ 148}; 149 150#define BPF_REG_SIZE 8 /* size of eBPF register in bytes */ 151 152struct bpf_stack_state { 153 struct bpf_reg_state spilled_ptr; 154 u8 slot_type[BPF_REG_SIZE]; 155}; 156 157struct bpf_reference_state { 158 /* Track each reference created with a unique id, even if the same 159 * instruction creates the reference multiple times (eg, via CALL). 160 */ 161 int id; 162 /* Instruction where the allocation of this reference occurred. This 163 * is used purely to inform the user of a reference leak. 164 */ 165 int insn_idx; 166}; 167 168/* state of the program: 169 * type of all registers and stack info 170 */ 171struct bpf_func_state { 172 struct bpf_reg_state regs[MAX_BPF_REG]; 173 /* index of call instruction that called into this func */ 174 int callsite; 175 /* stack frame number of this function state from pov of 176 * enclosing bpf_verifier_state. 177 * 0 = main function, 1 = first callee. 178 */ 179 u32 frameno; 180 /* subprog number == index within subprog_stack_depth 181 * zero == main subprog 182 */ 183 u32 subprogno; 184 185 /* The following fields should be last. See copy_func_state() */ 186 int acquired_refs; 187 struct bpf_reference_state *refs; 188 int allocated_stack; 189 struct bpf_stack_state *stack; 190}; 191 192struct bpf_idx_pair { 193 u32 prev_idx; 194 u32 idx; 195}; 196 197#define MAX_CALL_FRAMES 8 198struct bpf_verifier_state { 199 /* call stack tracking */ 200 struct bpf_func_state *frame[MAX_CALL_FRAMES]; 201 struct bpf_verifier_state *parent; 202 /* 203 * 'branches' field is the number of branches left to explore: 204 * 0 - all possible paths from this state reached bpf_exit or 205 * were safely pruned 206 * 1 - at least one path is being explored. 207 * This state hasn't reached bpf_exit 208 * 2 - at least two paths are being explored. 209 * This state is an immediate parent of two children. 210 * One is fallthrough branch with branches==1 and another 211 * state is pushed into stack (to be explored later) also with 212 * branches==1. The parent of this state has branches==1. 213 * The verifier state tree connected via 'parent' pointer looks like: 214 * 1 215 * 1 216 * 2 -> 1 (first 'if' pushed into stack) 217 * 1 218 * 2 -> 1 (second 'if' pushed into stack) 219 * 1 220 * 1 221 * 1 bpf_exit. 222 * 223 * Once do_check() reaches bpf_exit, it calls update_branch_counts() 224 * and the verifier state tree will look: 225 * 1 226 * 1 227 * 2 -> 1 (first 'if' pushed into stack) 228 * 1 229 * 1 -> 1 (second 'if' pushed into stack) 230 * 0 231 * 0 232 * 0 bpf_exit. 233 * After pop_stack() the do_check() will resume at second 'if'. 234 * 235 * If is_state_visited() sees a state with branches > 0 it means 236 * there is a loop. If such state is exactly equal to the current state 237 * it's an infinite loop. Note states_equal() checks for states 238 * equvalency, so two states being 'states_equal' does not mean 239 * infinite loop. The exact comparison is provided by 240 * states_maybe_looping() function. It's a stronger pre-check and 241 * much faster than states_equal(). 242 * 243 * This algorithm may not find all possible infinite loops or 244 * loop iteration count may be too high. 245 * In such cases BPF_COMPLEXITY_LIMIT_INSNS limit kicks in. 246 */ 247 u32 branches; 248 u32 insn_idx; 249 u32 curframe; 250 u32 active_spin_lock; 251 bool speculative; 252 253 /* first and last insn idx of this verifier state */ 254 u32 first_insn_idx; 255 u32 last_insn_idx; 256 /* jmp history recorded from first to last. 257 * backtracking is using it to go from last to first. 258 * For most states jmp_history_cnt is [0-3]. 259 * For loops can go up to ~40. 260 */ 261 struct bpf_idx_pair *jmp_history; 262 u32 jmp_history_cnt; 263}; 264 265#define bpf_get_spilled_reg(slot, frame) \ 266 (((slot < frame->allocated_stack / BPF_REG_SIZE) && \ 267 (frame->stack[slot].slot_type[0] == STACK_SPILL)) \ 268 ? &frame->stack[slot].spilled_ptr : NULL) 269 270/* Iterate over 'frame', setting 'reg' to either NULL or a spilled register. */ 271#define bpf_for_each_spilled_reg(iter, frame, reg) \ 272 for (iter = 0, reg = bpf_get_spilled_reg(iter, frame); \ 273 iter < frame->allocated_stack / BPF_REG_SIZE; \ 274 iter++, reg = bpf_get_spilled_reg(iter, frame)) 275 276/* linked list of verifier states used to prune search */ 277struct bpf_verifier_state_list { 278 struct bpf_verifier_state state; 279 struct bpf_verifier_state_list *next; 280 int miss_cnt, hit_cnt; 281}; 282 283/* Possible states for alu_state member. */ 284#define BPF_ALU_SANITIZE_SRC 1U 285#define BPF_ALU_SANITIZE_DST 2U 286#define BPF_ALU_NEG_VALUE (1U << 2) 287#define BPF_ALU_NON_POINTER (1U << 3) 288#define BPF_ALU_SANITIZE (BPF_ALU_SANITIZE_SRC | \ 289 BPF_ALU_SANITIZE_DST) 290 291struct bpf_insn_aux_data { 292 union { 293 enum bpf_reg_type ptr_type; /* pointer type for load/store insns */ 294 unsigned long map_state; /* pointer/poison value for maps */ 295 s32 call_imm; /* saved imm field of call insn */ 296 u32 alu_limit; /* limit for add/sub register with pointer */ 297 struct { 298 u32 map_index; /* index into used_maps[] */ 299 u32 map_off; /* offset from value base address */ 300 }; 301 }; 302 int ctx_field_size; /* the ctx field size for load insn, maybe 0 */ 303 int sanitize_stack_off; /* stack slot to be cleared */ 304 bool seen; /* this insn was processed by the verifier */ 305 bool zext_dst; /* this insn zero extends dst reg */ 306 u8 alu_state; /* used in combination with alu_limit */ 307 bool prune_point; 308 unsigned int orig_idx; /* original instruction index */ 309}; 310 311#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */ 312 313#define BPF_VERIFIER_TMP_LOG_SIZE 1024 314 315struct bpf_verifier_log { 316 u32 level; 317 char kbuf[BPF_VERIFIER_TMP_LOG_SIZE]; 318 char __user *ubuf; 319 u32 len_used; 320 u32 len_total; 321}; 322 323static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log) 324{ 325 return log->len_used >= log->len_total - 1; 326} 327 328#define BPF_LOG_LEVEL1 1 329#define BPF_LOG_LEVEL2 2 330#define BPF_LOG_STATS 4 331#define BPF_LOG_LEVEL (BPF_LOG_LEVEL1 | BPF_LOG_LEVEL2) 332#define BPF_LOG_MASK (BPF_LOG_LEVEL | BPF_LOG_STATS) 333 334static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log) 335{ 336 return log->level && log->ubuf && !bpf_verifier_log_full(log); 337} 338 339#define BPF_MAX_SUBPROGS 256 340 341struct bpf_subprog_info { 342 u32 start; /* insn idx of function entry point */ 343 u32 linfo_idx; /* The idx to the main_prog->aux->linfo */ 344 u16 stack_depth; /* max. stack depth used by this function */ 345}; 346 347/* single container for all structs 348 * one verifier_env per bpf_check() call 349 */ 350struct bpf_verifier_env { 351 u32 insn_idx; 352 u32 prev_insn_idx; 353 struct bpf_prog *prog; /* eBPF program being verified */ 354 const struct bpf_verifier_ops *ops; 355 struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */ 356 int stack_size; /* number of states to be processed */ 357 bool strict_alignment; /* perform strict pointer alignment checks */ 358 struct bpf_verifier_state *cur_state; /* current verifier state */ 359 struct bpf_verifier_state_list **explored_states; /* search pruning optimization */ 360 struct bpf_verifier_state_list *free_list; 361 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */ 362 u32 used_map_cnt; /* number of used maps */ 363 u32 id_gen; /* used to generate unique reg IDs */ 364 bool allow_ptr_leaks; 365 bool seen_direct_write; 366 struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */ 367 const struct bpf_line_info *prev_linfo; 368 struct bpf_verifier_log log; 369 struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1]; 370 struct { 371 int *insn_state; 372 int *insn_stack; 373 int cur_stack; 374 } cfg; 375 u32 subprog_cnt; 376 /* number of instructions analyzed by the verifier */ 377 u32 prev_insn_processed, insn_processed; 378 /* number of jmps, calls, exits analyzed so far */ 379 u32 prev_jmps_processed, jmps_processed; 380 /* total verification time */ 381 u64 verification_time; 382 /* maximum number of verifier states kept in 'branching' instructions */ 383 u32 max_states_per_insn; 384 /* total number of allocated verifier states */ 385 u32 total_states; 386 /* some states are freed during program analysis. 387 * this is peak number of states. this number dominates kernel 388 * memory consumption during verification 389 */ 390 u32 peak_states; 391 /* longest register parentage chain walked for liveness marking */ 392 u32 longest_mark_read_walk; 393}; 394 395__printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log *log, 396 const char *fmt, va_list args); 397__printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env, 398 const char *fmt, ...); 399 400static inline struct bpf_func_state *cur_func(struct bpf_verifier_env *env) 401{ 402 struct bpf_verifier_state *cur = env->cur_state; 403 404 return cur->frame[cur->curframe]; 405} 406 407static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env) 408{ 409 return cur_func(env)->regs; 410} 411 412int bpf_prog_offload_verifier_prep(struct bpf_prog *prog); 413int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env, 414 int insn_idx, int prev_insn_idx); 415int bpf_prog_offload_finalize(struct bpf_verifier_env *env); 416void 417bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off, 418 struct bpf_insn *insn); 419void 420bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt); 421 422#endif /* _LINUX_BPF_VERIFIER_H */ 423