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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 : : */
34 : : enum 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 : :
43 : : struct 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 : :
143 : : enum 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 : :
152 : : struct bpf_stack_state {
153 : : struct bpf_reg_state spilled_ptr;
154 : : u8 slot_type[BPF_REG_SIZE];
155 : : };
156 : :
157 : : struct 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 : : */
171 : : struct 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 : :
192 : : struct bpf_idx_pair {
193 : : u32 prev_idx;
194 : : u32 idx;
195 : : };
196 : :
197 : : #define MAX_CALL_FRAMES 8
198 : : struct 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 */
277 : : struct 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 : :
291 : : struct 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 : :
315 : : struct 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 : :
323 : : static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log)
324 : : {
325 : 0 : 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 : :
334 : : static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
335 : : {
336 [ # # # # : 3232 : return log->level && log->ubuf && !bpf_verifier_log_full(log);
# # - + #
# # # # #
# # # # #
# # # # #
# # # # #
# ]
337 : : }
338 : :
339 : : #define BPF_MAX_SUBPROGS 256
340 : :
341 : : struct 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 : : */
350 : : struct 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 : : bool test_state_freq; /* test verifier with different pruning frequency */
359 : : struct bpf_verifier_state *cur_state; /* current verifier state */
360 : : struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
361 : : struct bpf_verifier_state_list *free_list;
362 : : struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
363 : : u32 used_map_cnt; /* number of used maps */
364 : : u32 id_gen; /* used to generate unique reg IDs */
365 : : bool allow_ptr_leaks;
366 : : bool seen_direct_write;
367 : : struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
368 : : const struct bpf_line_info *prev_linfo;
369 : : struct bpf_verifier_log log;
370 : : struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
371 : : struct {
372 : : int *insn_state;
373 : : int *insn_stack;
374 : : int cur_stack;
375 : : } cfg;
376 : : u32 subprog_cnt;
377 : : /* number of instructions analyzed by the verifier */
378 : : u32 prev_insn_processed, insn_processed;
379 : : /* number of jmps, calls, exits analyzed so far */
380 : : u32 prev_jmps_processed, jmps_processed;
381 : : /* total verification time */
382 : : u64 verification_time;
383 : : /* maximum number of verifier states kept in 'branching' instructions */
384 : : u32 max_states_per_insn;
385 : : /* total number of allocated verifier states */
386 : : u32 total_states;
387 : : /* some states are freed during program analysis.
388 : : * this is peak number of states. this number dominates kernel
389 : : * memory consumption during verification
390 : : */
391 : : u32 peak_states;
392 : : /* longest register parentage chain walked for liveness marking */
393 : : u32 longest_mark_read_walk;
394 : : };
395 : :
396 : : __printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log *log,
397 : : const char *fmt, va_list args);
398 : : __printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
399 : : const char *fmt, ...);
400 : :
401 : : static inline struct bpf_func_state *cur_func(struct bpf_verifier_env *env)
402 : : {
403 : 368448 : struct bpf_verifier_state *cur = env->cur_state;
404 : :
405 : 368448 : return cur->frame[cur->curframe];
406 : : }
407 : :
408 : : static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env)
409 : : {
410 : 347440 : return cur_func(env)->regs;
411 : : }
412 : :
413 : : int bpf_prog_offload_verifier_prep(struct bpf_prog *prog);
414 : : int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env,
415 : : int insn_idx, int prev_insn_idx);
416 : : int bpf_prog_offload_finalize(struct bpf_verifier_env *env);
417 : : void
418 : : bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off,
419 : : struct bpf_insn *insn);
420 : : void
421 : : bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
422 : :
423 : : #endif /* _LINUX_BPF_VERIFIER_H */
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