projects / deliverable / linux.git / blame
? search:
summary | shortlog | log | commit | commitdiff | tree
blob | blame (incremental) | history | HEAD
Merge branch '40GbE' of git://git.kernel.org/pub/scm/linux/kernel/git/jkirsher/next...
[deliverable/linux.git] / kernel / bpf / verifier.c
CommitLineData
51580e79
AS		 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
17a52670
AS		 128/* types of values stored in eBPF registers */
129enum bpf_reg_type {
130 NOT_INIT = 0, /* nothing was written into register */
131 UNKNOWN_VALUE, /* reg doesn't contain a valid pointer */
132 PTR_TO_CTX, /* reg points to bpf_context */
133 CONST_PTR_TO_MAP, /* reg points to struct bpf_map */
134 PTR_TO_MAP_VALUE, /* reg points to map element value */
135 PTR_TO_MAP_VALUE_OR_NULL,/* points to map elem value or NULL */
136 FRAME_PTR, /* reg == frame_pointer */
137 PTR_TO_STACK, /* reg == frame_pointer + imm */
138 CONST_IMM, /* constant integer value */
139};
140
141struct reg_state {
142 enum bpf_reg_type type;
143 union {
144 /* valid when type == CONST_IMM | PTR_TO_STACK */
4923ec0b 145 long imm;
17a52670
AS		 146
147 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
148 * PTR_TO_MAP_VALUE_OR_NULL
149 */
150 struct bpf_map *map_ptr;
151 };
152};
153
154enum bpf_stack_slot_type {
155 STACK_INVALID, /* nothing was stored in this stack slot */
9c399760 156 STACK_SPILL, /* register spilled into stack */
17a52670
AS		 157 STACK_MISC /* BPF program wrote some data into this slot */
158};
159
9c399760 160#define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
17a52670
AS		 161
162/* state of the program:
163 * type of all registers and stack info
164 */
165struct verifier_state {
166 struct reg_state regs[MAX_BPF_REG];
9c399760
AS		 167 u8 stack_slot_type[MAX_BPF_STACK];
168 struct reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE];
17a52670
AS		 169};
170
171/* linked list of verifier states used to prune search */
172struct verifier_state_list {
173 struct verifier_state state;
174 struct verifier_state_list *next;
175};
176
177/* verifier_state + insn_idx are pushed to stack when branch is encountered */
178struct verifier_stack_elem {
179 /* verifer state is 'st'
180 * before processing instruction 'insn_idx'
181 * and after processing instruction 'prev_insn_idx'
182 */
183 struct verifier_state st;
184 int insn_idx;
185 int prev_insn_idx;
186 struct verifier_stack_elem *next;
187};
188
0246e64d
AS		 189#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
190
cbd35700
AS		 191/* single container for all structs
192 * one verifier_env per bpf_check() call
193 */
194struct verifier_env {
0246e64d 195 struct bpf_prog *prog; /* eBPF program being verified */
17a52670
AS		 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 */
f1bca824 199 struct verifier_state_list **explored_states; /* search pruning optimization */
0246e64d
AS		 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 */
1be7f75d 202 bool allow_ptr_leaks;
cbd35700
AS		 203};
204
07016151
DB		 205#define BPF_COMPLEXITY_LIMIT_INSNS 65536
206#define BPF_COMPLEXITY_LIMIT_STACK 1024
207
33ff9823
DB		 208struct bpf_call_arg_meta {
209 struct bpf_map *map_ptr;
435faee1
DB		 210 bool raw_mode;
211 int regno;
212 int access_size;
33ff9823
DB		 213};
214
cbd35700
AS		 215/* verbose verifier prints what it's seeing
216 * bpf_check() is called under lock, so no race to access these global vars
217 */
218static u32 log_level, log_size, log_len;
219static char *log_buf;
220
221static DEFINE_MUTEX(bpf_verifier_lock);
222
223/* log_level controls verbosity level of eBPF verifier.
224 * verbose() is used to dump the verification trace to the log, so the user
225 * can figure out what's wrong with the program
226 */
1d056d9c 227static __printf(1, 2) void verbose(const char *fmt, ...)
cbd35700
AS		 228{
229 va_list args;
230
231 if (log_level == 0 || log_len >= log_size - 1)
232 return;
233
234 va_start(args, fmt);
235 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args);
236 va_end(args);
237}
238
17a52670
AS		 239/* string representation of 'enum bpf_reg_type' */
240static const char * const reg_type_str[] = {
241 [NOT_INIT] = "?",
242 [UNKNOWN_VALUE] = "inv",
243 [PTR_TO_CTX] = "ctx",
244 [CONST_PTR_TO_MAP] = "map_ptr",
245 [PTR_TO_MAP_VALUE] = "map_value",
246 [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null",
247 [FRAME_PTR] = "fp",
248 [PTR_TO_STACK] = "fp",
249 [CONST_IMM] = "imm",
250};
251
252static 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)
4923ec0b 263 verbose("%ld", env->cur_state.regs[i].imm);
17a52670
AS		 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 }
9c399760
AS		 270 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
271 if (env->cur_state.stack_slot_type[i] == STACK_SPILL)
17a52670 272 verbose(" fp%d=%s", -MAX_BPF_STACK + i,
9c399760 273 reg_type_str[env->cur_state.spilled_regs[i / BPF_REG_SIZE].type]);
17a52670
AS		 274 }
275 verbose("\n");
276}
277
cbd35700
AS		 278static 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
687f0715 289static const char *const bpf_alu_string[16] = {
cbd35700
AS		 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
306static 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
687f0715 313static const char *const bpf_jmp_string[16] = {
cbd35700
AS		 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
326static 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
17a52670
AS		 423static 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
442static 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++;
07016151 457 if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) {
17a52670
AS		 458 verbose("BPF program is too complex\n");
459 goto err;
460 }
461 return &elem->st;
462err:
463 /* pop all elements and return */
464 while (pop_stack(env, NULL) >= 0);
465 return NULL;
466}
467
468#define CALLER_SAVED_REGS 6
469static 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
473static 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;
17a52670
AS		 480 }
481
482 /* frame pointer */
483 regs[BPF_REG_FP].type = FRAME_PTR;
484
485 /* 1st arg to a function */
486 regs[BPF_REG_1].type = PTR_TO_CTX;
487}
488
489static void mark_reg_unknown_value(struct reg_state *regs, u32 regno)
490{
491 BUG_ON(regno >= MAX_BPF_REG);
492 regs[regno].type = UNKNOWN_VALUE;
493 regs[regno].imm = 0;
17a52670
AS		 494}
495
496enum reg_arg_type {
497 SRC_OP, /* register is used as source operand */
498 DST_OP, /* register is used as destination operand */
499 DST_OP_NO_MARK /* same as above, check only, don't mark */
500};
501
502static int check_reg_arg(struct reg_state *regs, u32 regno,
503 enum reg_arg_type t)
504{
505 if (regno >= MAX_BPF_REG) {
506 verbose("R%d is invalid\n", regno);
507 return -EINVAL;
508 }
509
510 if (t == SRC_OP) {
511 /* check whether register used as source operand can be read */
512 if (regs[regno].type == NOT_INIT) {
513 verbose("R%d !read_ok\n", regno);
514 return -EACCES;
515 }
516 } else {
517 /* check whether register used as dest operand can be written to */
518 if (regno == BPF_REG_FP) {
519 verbose("frame pointer is read only\n");
520 return -EACCES;
521 }
522 if (t == DST_OP)
523 mark_reg_unknown_value(regs, regno);
524 }
525 return 0;
526}
527
528static int bpf_size_to_bytes(int bpf_size)
529{
530 if (bpf_size == BPF_W)
531 return 4;
532 else if (bpf_size == BPF_H)
533 return 2;
534 else if (bpf_size == BPF_B)
535 return 1;
536 else if (bpf_size == BPF_DW)
537 return 8;
538 else
539 return -EINVAL;
540}
541
1be7f75d
AS		 542static bool is_spillable_regtype(enum bpf_reg_type type)
543{
544 switch (type) {
545 case PTR_TO_MAP_VALUE:
546 case PTR_TO_MAP_VALUE_OR_NULL:
547 case PTR_TO_STACK:
548 case PTR_TO_CTX:
549 case FRAME_PTR:
550 case CONST_PTR_TO_MAP:
551 return true;
552 default:
553 return false;
554 }
555}
556
17a52670
AS		 557/* check_stack_read/write functions track spill/fill of registers,
558 * stack boundary and alignment are checked in check_mem_access()
559 */
560static int check_stack_write(struct verifier_state *state, int off, int size,
561 int value_regno)
562{
17a52670 563 int i;
9c399760
AS		 564 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0,
565 * so it's aligned access and [off, off + size) are within stack limits
566 */
17a52670
AS		 567
568 if (value_regno >= 0 &&
1be7f75d 569 is_spillable_regtype(state->regs[value_regno].type)) {
17a52670
AS		 570
571 /* register containing pointer is being spilled into stack */
9c399760 572 if (size != BPF_REG_SIZE) {
17a52670
AS		 573 verbose("invalid size of register spill\n");
574 return -EACCES;
575 }
576
17a52670 577 /* save register state */
9c399760
AS		 578 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
579 state->regs[value_regno];
17a52670 580
9c399760
AS		 581 for (i = 0; i < BPF_REG_SIZE; i++)
582 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL;
583 } else {
17a52670 584 /* regular write of data into stack */
9c399760
AS		 585 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
586 (struct reg_state) {};
587
588 for (i = 0; i < size; i++)
589 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC;
17a52670
AS		 590 }
591 return 0;
592}
593
594static int check_stack_read(struct verifier_state *state, int off, int size,
595 int value_regno)
596{
9c399760 597 u8 *slot_type;
17a52670 598 int i;
17a52670 599
9c399760 600 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off];
17a52670 601
9c399760
AS		 602 if (slot_type[0] == STACK_SPILL) {
603 if (size != BPF_REG_SIZE) {
17a52670
AS		 604 verbose("invalid size of register spill\n");
605 return -EACCES;
606 }
9c399760
AS		 607 for (i = 1; i < BPF_REG_SIZE; i++) {
608 if (slot_type[i] != STACK_SPILL) {
17a52670
AS		 609 verbose("corrupted spill memory\n");
610 return -EACCES;
611 }
612 }
613
614 if (value_regno >= 0)
615 /* restore register state from stack */
9c399760
AS		 616 state->regs[value_regno] =
617 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE];
17a52670
AS		 618 return 0;
619 } else {
620 for (i = 0; i < size; i++) {
9c399760 621 if (slot_type[i] != STACK_MISC) {
17a52670
AS		 622 verbose("invalid read from stack off %d+%d size %d\n",
623 off, i, size);
624 return -EACCES;
625 }
626 }
627 if (value_regno >= 0)
628 /* have read misc data from the stack */
629 mark_reg_unknown_value(state->regs, value_regno);
630 return 0;
631 }
632}
633
634/* check read/write into map element returned by bpf_map_lookup_elem() */
635static int check_map_access(struct verifier_env *env, u32 regno, int off,
636 int size)
637{
638 struct bpf_map *map = env->cur_state.regs[regno].map_ptr;
639
640 if (off < 0 || off + size > map->value_size) {
641 verbose("invalid access to map value, value_size=%d off=%d size=%d\n",
642 map->value_size, off, size);
643 return -EACCES;
644 }
645 return 0;
646}
647
648/* check access to 'struct bpf_context' fields */
649static int check_ctx_access(struct verifier_env *env, int off, int size,
650 enum bpf_access_type t)
651{
652 if (env->prog->aux->ops->is_valid_access &&
32bbe007
AS		 653 env->prog->aux->ops->is_valid_access(off, size, t)) {
654 /* remember the offset of last byte accessed in ctx */
655 if (env->prog->aux->max_ctx_offset < off + size)
656 env->prog->aux->max_ctx_offset = off + size;
17a52670 657 return 0;
32bbe007 658 }
17a52670
AS		 659
660 verbose("invalid bpf_context access off=%d size=%d\n", off, size);
661 return -EACCES;
662}
663
1be7f75d
AS		 664static bool is_pointer_value(struct verifier_env *env, int regno)
665{
666 if (env->allow_ptr_leaks)
667 return false;
668
669 switch (env->cur_state.regs[regno].type) {
670 case UNKNOWN_VALUE:
671 case CONST_IMM:
672 return false;
673 default:
674 return true;
675 }
676}
677
17a52670
AS		 678/* check whether memory at (regno + off) is accessible for t = (read | write)
679 * if t==write, value_regno is a register which value is stored into memory
680 * if t==read, value_regno is a register which will receive the value from memory
681 * if t==write && value_regno==-1, some unknown value is stored into memory
682 * if t==read && value_regno==-1, don't care what we read from memory
683 */
684static int check_mem_access(struct verifier_env *env, u32 regno, int off,
685 int bpf_size, enum bpf_access_type t,
686 int value_regno)
687{
688 struct verifier_state *state = &env->cur_state;
689 int size, err = 0;
690
24b4d2ab
AG		 691 if (state->regs[regno].type == PTR_TO_STACK)
692 off += state->regs[regno].imm;
693
17a52670
AS		 694 size = bpf_size_to_bytes(bpf_size);
695 if (size < 0)
696 return size;
697
698 if (off % size != 0) {
699 verbose("misaligned access off %d size %d\n", off, size);
700 return -EACCES;
701 }
702
703 if (state->regs[regno].type == PTR_TO_MAP_VALUE) {
1be7f75d
AS		 704 if (t == BPF_WRITE && value_regno >= 0 &&
705 is_pointer_value(env, value_regno)) {
706 verbose("R%d leaks addr into map\n", value_regno);
707 return -EACCES;
708 }
17a52670
AS		 709 err = check_map_access(env, regno, off, size);
710 if (!err && t == BPF_READ && value_regno >= 0)
711 mark_reg_unknown_value(state->regs, value_regno);
712
713 } else if (state->regs[regno].type == PTR_TO_CTX) {
1be7f75d
AS		 714 if (t == BPF_WRITE && value_regno >= 0 &&
715 is_pointer_value(env, value_regno)) {
716 verbose("R%d leaks addr into ctx\n", value_regno);
717 return -EACCES;
718 }
17a52670
AS		 719 err = check_ctx_access(env, off, size, t);
720 if (!err && t == BPF_READ && value_regno >= 0)
721 mark_reg_unknown_value(state->regs, value_regno);
722
24b4d2ab
AG		 723 } else if (state->regs[regno].type == FRAME_PTR ||
724 state->regs[regno].type == PTR_TO_STACK) {
17a52670
AS		 725 if (off >= 0 || off < -MAX_BPF_STACK) {
726 verbose("invalid stack off=%d size=%d\n", off, size);
727 return -EACCES;
728 }
1be7f75d
AS		 729 if (t == BPF_WRITE) {
730 if (!env->allow_ptr_leaks &&
731 state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL &&
732 size != BPF_REG_SIZE) {
733 verbose("attempt to corrupt spilled pointer on stack\n");
734 return -EACCES;
735 }
17a52670 736 err = check_stack_write(state, off, size, value_regno);
1be7f75d 737 } else {
17a52670 738 err = check_stack_read(state, off, size, value_regno);
1be7f75d 739 }
17a52670
AS		 740 } else {
741 verbose("R%d invalid mem access '%s'\n",
742 regno, reg_type_str[state->regs[regno].type]);
743 return -EACCES;
744 }
745 return err;
746}
747
748static int check_xadd(struct verifier_env *env, struct bpf_insn *insn)
749{
750 struct reg_state *regs = env->cur_state.regs;
751 int err;
752
753 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) ||
754 insn->imm != 0) {
755 verbose("BPF_XADD uses reserved fields\n");
756 return -EINVAL;
757 }
758
759 /* check src1 operand */
760 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
761 if (err)
762 return err;
763
764 /* check src2 operand */
765 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
766 if (err)
767 return err;
768
769 /* check whether atomic_add can read the memory */
770 err = check_mem_access(env, insn->dst_reg, insn->off,
771 BPF_SIZE(insn->code), BPF_READ, -1);
772 if (err)
773 return err;
774
775 /* check whether atomic_add can write into the same memory */
776 return check_mem_access(env, insn->dst_reg, insn->off,
777 BPF_SIZE(insn->code), BPF_WRITE, -1);
778}
779
780/* when register 'regno' is passed into function that will read 'access_size'
781 * bytes from that pointer, make sure that it's within stack boundary
782 * and all elements of stack are initialized
783 */
8e2fe1d9 784static int check_stack_boundary(struct verifier_env *env, int regno,
435faee1
DB		 785 int access_size, bool zero_size_allowed,
786 struct bpf_call_arg_meta *meta)
17a52670
AS		 787{
788 struct verifier_state *state = &env->cur_state;
789 struct reg_state *regs = state->regs;
790 int off, i;
791
8e2fe1d9
DB		 792 if (regs[regno].type != PTR_TO_STACK) {
793 if (zero_size_allowed && access_size == 0 &&
794 regs[regno].type == CONST_IMM &&
795 regs[regno].imm == 0)
796 return 0;
797
798 verbose("R%d type=%s expected=%s\n", regno,
799 reg_type_str[regs[regno].type],
800 reg_type_str[PTR_TO_STACK]);
17a52670 801 return -EACCES;
8e2fe1d9 802 }
17a52670
AS		 803
804 off = regs[regno].imm;
805 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
806 access_size <= 0) {
807 verbose("invalid stack type R%d off=%d access_size=%d\n",
808 regno, off, access_size);
809 return -EACCES;
810 }
811
435faee1
DB		 812 if (meta && meta->raw_mode) {
813 meta->access_size = access_size;
814 meta->regno = regno;
815 return 0;
816 }
817
17a52670 818 for (i = 0; i < access_size; i++) {
9c399760 819 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) {
17a52670
AS		 820 verbose("invalid indirect read from stack off %d+%d size %d\n",
821 off, i, access_size);
822 return -EACCES;
823 }
824 }
825 return 0;
826}
827
828static int check_func_arg(struct verifier_env *env, u32 regno,
33ff9823
DB		 829 enum bpf_arg_type arg_type,
830 struct bpf_call_arg_meta *meta)
17a52670
AS		 831{
832 struct reg_state *reg = env->cur_state.regs + regno;
833 enum bpf_reg_type expected_type;
834 int err = 0;
835
80f1d68c 836 if (arg_type == ARG_DONTCARE)
17a52670
AS		 837 return 0;
838
839 if (reg->type == NOT_INIT) {
840 verbose("R%d !read_ok\n", regno);
841 return -EACCES;
842 }
843
1be7f75d
AS		 844 if (arg_type == ARG_ANYTHING) {
845 if (is_pointer_value(env, regno)) {
846 verbose("R%d leaks addr into helper function\n", regno);
847 return -EACCES;
848 }
80f1d68c 849 return 0;
1be7f75d 850 }
80f1d68c 851
8e2fe1d9 852 if (arg_type == ARG_PTR_TO_MAP_KEY ||
17a52670
AS		 853 arg_type == ARG_PTR_TO_MAP_VALUE) {
854 expected_type = PTR_TO_STACK;
8e2fe1d9
DB		 855 } else if (arg_type == ARG_CONST_STACK_SIZE ||
856 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
17a52670
AS		 857 expected_type = CONST_IMM;
858 } else if (arg_type == ARG_CONST_MAP_PTR) {
859 expected_type = CONST_PTR_TO_MAP;
608cd71a
AS		 860 } else if (arg_type == ARG_PTR_TO_CTX) {
861 expected_type = PTR_TO_CTX;
435faee1
DB		 862 } else if (arg_type == ARG_PTR_TO_STACK ||
863 arg_type == ARG_PTR_TO_RAW_STACK) {
8e2fe1d9
DB		 864 expected_type = PTR_TO_STACK;
865 /* One exception here. In case function allows for NULL to be
866 * passed in as argument, it's a CONST_IMM type. Final test
867 * happens during stack boundary checking.
868 */
869 if (reg->type == CONST_IMM && reg->imm == 0)
870 expected_type = CONST_IMM;
435faee1 871 meta->raw_mode = arg_type == ARG_PTR_TO_RAW_STACK;
17a52670
AS		 872 } else {
873 verbose("unsupported arg_type %d\n", arg_type);
874 return -EFAULT;
875 }
876
877 if (reg->type != expected_type) {
878 verbose("R%d type=%s expected=%s\n", regno,
879 reg_type_str[reg->type], reg_type_str[expected_type]);
880 return -EACCES;
881 }
882
883 if (arg_type == ARG_CONST_MAP_PTR) {
884 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */
33ff9823 885 meta->map_ptr = reg->map_ptr;
17a52670
AS		 886 } else if (arg_type == ARG_PTR_TO_MAP_KEY) {
887 /* bpf_map_xxx(..., map_ptr, ..., key) call:
888 * check that [key, key + map->key_size) are within
889 * stack limits and initialized
890 */
33ff9823 891 if (!meta->map_ptr) {
17a52670
AS		 892 /* in function declaration map_ptr must come before
893 * map_key, so that it's verified and known before
894 * we have to check map_key here. Otherwise it means
895 * that kernel subsystem misconfigured verifier
896 */
897 verbose("invalid map_ptr to access map->key\n");
898 return -EACCES;
899 }
33ff9823 900 err = check_stack_boundary(env, regno, meta->map_ptr->key_size,
435faee1 901 false, NULL);
17a52670
AS		 902 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
903 /* bpf_map_xxx(..., map_ptr, ..., value) call:
904 * check [value, value + map->value_size) validity
905 */
33ff9823 906 if (!meta->map_ptr) {
17a52670
AS		 907 /* kernel subsystem misconfigured verifier */
908 verbose("invalid map_ptr to access map->value\n");
909 return -EACCES;
910 }
33ff9823 911 err = check_stack_boundary(env, regno,
435faee1
DB		 912 meta->map_ptr->value_size,
913 false, NULL);
8e2fe1d9
DB		 914 } else if (arg_type == ARG_CONST_STACK_SIZE ||
915 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
916 bool zero_size_allowed = (arg_type == ARG_CONST_STACK_SIZE_OR_ZERO);
17a52670 917
17a52670
AS		 918 /* bpf_xxx(..., buf, len) call will access 'len' bytes
919 * from stack pointer 'buf'. Check it
920 * note: regno == len, regno - 1 == buf
921 */
922 if (regno == 0) {
923 /* kernel subsystem misconfigured verifier */
924 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n");
925 return -EACCES;
926 }
8e2fe1d9 927 err = check_stack_boundary(env, regno - 1, reg->imm,
435faee1 928 zero_size_allowed, meta);
17a52670
AS		 929 }
930
931 return err;
932}
933
35578d79
KX		 934static int check_map_func_compatibility(struct bpf_map *map, int func_id)
935{
35578d79
KX		 936 if (!map)
937 return 0;
938
6aff67c8
AS		 939 /* We need a two way check, first is from map perspective ... */
940 switch (map->map_type) {
941 case BPF_MAP_TYPE_PROG_ARRAY:
942 if (func_id != BPF_FUNC_tail_call)
943 goto error;
944 break;
945 case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
946 if (func_id != BPF_FUNC_perf_event_read &&
947 func_id != BPF_FUNC_perf_event_output)
948 goto error;
949 break;
950 case BPF_MAP_TYPE_STACK_TRACE:
951 if (func_id != BPF_FUNC_get_stackid)
952 goto error;
953 break;
954 default:
955 break;
956 }
957
958 /* ... and second from the function itself. */
959 switch (func_id) {
960 case BPF_FUNC_tail_call:
961 if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
962 goto error;
963 break;
964 case BPF_FUNC_perf_event_read:
965 case BPF_FUNC_perf_event_output:
966 if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
967 goto error;
968 break;
969 case BPF_FUNC_get_stackid:
970 if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
971 goto error;
972 break;
973 default:
974 break;
35578d79
KX		 975 }
976
977 return 0;
6aff67c8
AS		 978error:
979 verbose("cannot pass map_type %d into func %d\n",
980 map->map_type, func_id);
981 return -EINVAL;
35578d79
KX		 982}
983
435faee1
DB		 984static int check_raw_mode(const struct bpf_func_proto *fn)
985{
986 int count = 0;
987
988 if (fn->arg1_type == ARG_PTR_TO_RAW_STACK)
989 count++;
990 if (fn->arg2_type == ARG_PTR_TO_RAW_STACK)
991 count++;
992 if (fn->arg3_type == ARG_PTR_TO_RAW_STACK)
993 count++;
994 if (fn->arg4_type == ARG_PTR_TO_RAW_STACK)
995 count++;
996 if (fn->arg5_type == ARG_PTR_TO_RAW_STACK)
997 count++;
998
999 return count > 1 ? -EINVAL : 0;
1000}
1001
17a52670
AS		 1002static int check_call(struct verifier_env *env, int func_id)
1003{
1004 struct verifier_state *state = &env->cur_state;
1005 const struct bpf_func_proto *fn = NULL;
1006 struct reg_state *regs = state->regs;
17a52670 1007 struct reg_state *reg;
33ff9823 1008 struct bpf_call_arg_meta meta;
17a52670
AS		 1009 int i, err;
1010
1011 /* find function prototype */
1012 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
1013 verbose("invalid func %d\n", func_id);
1014 return -EINVAL;
1015 }
1016
1017 if (env->prog->aux->ops->get_func_proto)
1018 fn = env->prog->aux->ops->get_func_proto(func_id);
1019
1020 if (!fn) {
1021 verbose("unknown func %d\n", func_id);
1022 return -EINVAL;
1023 }
1024
1025 /* eBPF programs must be GPL compatible to use GPL-ed functions */
24701ece 1026 if (!env->prog->gpl_compatible && fn->gpl_only) {
17a52670
AS		 1027 verbose("cannot call GPL only function from proprietary program\n");
1028 return -EINVAL;
1029 }
1030
33ff9823
DB		 1031 memset(&meta, 0, sizeof(meta));
1032
435faee1
DB		 1033 /* We only support one arg being in raw mode at the moment, which
1034 * is sufficient for the helper functions we have right now.
1035 */
1036 err = check_raw_mode(fn);
1037 if (err) {
1038 verbose("kernel subsystem misconfigured func %d\n", func_id);
1039 return err;
1040 }
1041
17a52670 1042 /* check args */
33ff9823 1043 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta);
17a52670
AS		 1044 if (err)
1045 return err;
33ff9823 1046 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta);
17a52670
AS		 1047 if (err)
1048 return err;
33ff9823 1049 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta);
17a52670
AS		 1050 if (err)
1051 return err;
33ff9823 1052 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta);
17a52670
AS		 1053 if (err)
1054 return err;
33ff9823 1055 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta);
17a52670
AS		 1056 if (err)
1057 return err;
1058
435faee1
DB		 1059 /* Mark slots with STACK_MISC in case of raw mode, stack offset
1060 * is inferred from register state.
1061 */
1062 for (i = 0; i < meta.access_size; i++) {
1063 err = check_mem_access(env, meta.regno, i, BPF_B, BPF_WRITE, -1);
1064 if (err)
1065 return err;
1066 }
1067
17a52670
AS		 1068 /* reset caller saved regs */
1069 for (i = 0; i < CALLER_SAVED_REGS; i++) {
1070 reg = regs + caller_saved[i];
1071 reg->type = NOT_INIT;
1072 reg->imm = 0;
1073 }
1074
1075 /* update return register */
1076 if (fn->ret_type == RET_INTEGER) {
1077 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1078 } else if (fn->ret_type == RET_VOID) {
1079 regs[BPF_REG_0].type = NOT_INIT;
1080 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) {
1081 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
1082 /* remember map_ptr, so that check_map_access()
1083 * can check 'value_size' boundary of memory access
1084 * to map element returned from bpf_map_lookup_elem()
1085 */
33ff9823 1086 if (meta.map_ptr == NULL) {
17a52670
AS		 1087 verbose("kernel subsystem misconfigured verifier\n");
1088 return -EINVAL;
1089 }
33ff9823 1090 regs[BPF_REG_0].map_ptr = meta.map_ptr;
17a52670
AS		 1091 } else {
1092 verbose("unknown return type %d of func %d\n",
1093 fn->ret_type, func_id);
1094 return -EINVAL;
1095 }
04fd61ab 1096
33ff9823 1097 err = check_map_func_compatibility(meta.map_ptr, func_id);
35578d79
KX		 1098 if (err)
1099 return err;
04fd61ab 1100
17a52670
AS		 1101 return 0;
1102}
1103
1104/* check validity of 32-bit and 64-bit arithmetic operations */
1be7f75d 1105static int check_alu_op(struct verifier_env *env, struct bpf_insn *insn)
17a52670 1106{
1be7f75d 1107 struct reg_state *regs = env->cur_state.regs;
17a52670
AS		 1108 u8 opcode = BPF_OP(insn->code);
1109 int err;
1110
1111 if (opcode == BPF_END || opcode == BPF_NEG) {
1112 if (opcode == BPF_NEG) {
1113 if (BPF_SRC(insn->code) != 0 ||
1114 insn->src_reg != BPF_REG_0 ||
1115 insn->off != 0 || insn->imm != 0) {
1116 verbose("BPF_NEG uses reserved fields\n");
1117 return -EINVAL;
1118 }
1119 } else {
1120 if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
1121 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) {
1122 verbose("BPF_END uses reserved fields\n");
1123 return -EINVAL;
1124 }
1125 }
1126
1127 /* check src operand */
1128 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1129 if (err)
1130 return err;
1131
1be7f75d
AS		 1132 if (is_pointer_value(env, insn->dst_reg)) {
1133 verbose("R%d pointer arithmetic prohibited\n",
1134 insn->dst_reg);
1135 return -EACCES;
1136 }
1137
17a52670
AS		 1138 /* check dest operand */
1139 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1140 if (err)
1141 return err;
1142
1143 } else if (opcode == BPF_MOV) {
1144
1145 if (BPF_SRC(insn->code) == BPF_X) {
1146 if (insn->imm != 0 || insn->off != 0) {
1147 verbose("BPF_MOV uses reserved fields\n");
1148 return -EINVAL;
1149 }
1150
1151 /* check src operand */
1152 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1153 if (err)
1154 return err;
1155 } else {
1156 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1157 verbose("BPF_MOV uses reserved fields\n");
1158 return -EINVAL;
1159 }
1160 }
1161
1162 /* check dest operand */
1163 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1164 if (err)
1165 return err;
1166
1167 if (BPF_SRC(insn->code) == BPF_X) {
1168 if (BPF_CLASS(insn->code) == BPF_ALU64) {
1169 /* case: R1 = R2
1170 * copy register state to dest reg
1171 */
1172 regs[insn->dst_reg] = regs[insn->src_reg];
1173 } else {
1be7f75d
AS		 1174 if (is_pointer_value(env, insn->src_reg)) {
1175 verbose("R%d partial copy of pointer\n",
1176 insn->src_reg);
1177 return -EACCES;
1178 }
17a52670
AS		 1179 regs[insn->dst_reg].type = UNKNOWN_VALUE;
1180 regs[insn->dst_reg].map_ptr = NULL;
1181 }
1182 } else {
1183 /* case: R = imm
1184 * remember the value we stored into this reg
1185 */
1186 regs[insn->dst_reg].type = CONST_IMM;
1187 regs[insn->dst_reg].imm = insn->imm;
1188 }
1189
1190 } else if (opcode > BPF_END) {
1191 verbose("invalid BPF_ALU opcode %x\n", opcode);
1192 return -EINVAL;
1193
1194 } else { /* all other ALU ops: and, sub, xor, add, ... */
1195
1196 bool stack_relative = false;
1197
1198 if (BPF_SRC(insn->code) == BPF_X) {
1199 if (insn->imm != 0 || insn->off != 0) {
1200 verbose("BPF_ALU uses reserved fields\n");
1201 return -EINVAL;
1202 }
1203 /* check src1 operand */
1204 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1205 if (err)
1206 return err;
1207 } else {
1208 if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
1209 verbose("BPF_ALU uses reserved fields\n");
1210 return -EINVAL;
1211 }
1212 }
1213
1214 /* check src2 operand */
1215 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1216 if (err)
1217 return err;
1218
1219 if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
1220 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
1221 verbose("div by zero\n");
1222 return -EINVAL;
1223 }
1224
229394e8
RV		 1225 if ((opcode == BPF_LSH || opcode == BPF_RSH ||
1226 opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) {
1227 int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32;
1228
1229 if (insn->imm < 0 || insn->imm >= size) {
1230 verbose("invalid shift %d\n", insn->imm);
1231 return -EINVAL;
1232 }
1233 }
1234
17a52670
AS		 1235 /* pattern match 'bpf_add Rx, imm' instruction */
1236 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 &&
1237 regs[insn->dst_reg].type == FRAME_PTR &&
1be7f75d 1238 BPF_SRC(insn->code) == BPF_K) {
17a52670 1239 stack_relative = true;
1be7f75d
AS		 1240 } else if (is_pointer_value(env, insn->dst_reg)) {
1241 verbose("R%d pointer arithmetic prohibited\n",
1242 insn->dst_reg);
1243 return -EACCES;
1244 } else if (BPF_SRC(insn->code) == BPF_X &&
1245 is_pointer_value(env, insn->src_reg)) {
1246 verbose("R%d pointer arithmetic prohibited\n",
1247 insn->src_reg);
1248 return -EACCES;
1249 }
17a52670
AS		 1250
1251 /* check dest operand */
1252 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1253 if (err)
1254 return err;
1255
1256 if (stack_relative) {
1257 regs[insn->dst_reg].type = PTR_TO_STACK;
1258 regs[insn->dst_reg].imm = insn->imm;
1259 }
1260 }
1261
1262 return 0;
1263}
1264
1265static int check_cond_jmp_op(struct verifier_env *env,
1266 struct bpf_insn *insn, int *insn_idx)
1267{
1268 struct reg_state *regs = env->cur_state.regs;
1269 struct verifier_state *other_branch;
1270 u8 opcode = BPF_OP(insn->code);
1271 int err;
1272
1273 if (opcode > BPF_EXIT) {
1274 verbose("invalid BPF_JMP opcode %x\n", opcode);
1275 return -EINVAL;
1276 }
1277
1278 if (BPF_SRC(insn->code) == BPF_X) {
1279 if (insn->imm != 0) {
1280 verbose("BPF_JMP uses reserved fields\n");
1281 return -EINVAL;
1282 }
1283
1284 /* check src1 operand */
1285 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1286 if (err)
1287 return err;
1be7f75d
AS		 1288
1289 if (is_pointer_value(env, insn->src_reg)) {
1290 verbose("R%d pointer comparison prohibited\n",
1291 insn->src_reg);
1292 return -EACCES;
1293 }
17a52670
AS		 1294 } else {
1295 if (insn->src_reg != BPF_REG_0) {
1296 verbose("BPF_JMP uses reserved fields\n");
1297 return -EINVAL;
1298 }
1299 }
1300
1301 /* check src2 operand */
1302 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1303 if (err)
1304 return err;
1305
1306 /* detect if R == 0 where R was initialized to zero earlier */
1307 if (BPF_SRC(insn->code) == BPF_K &&
1308 (opcode == BPF_JEQ || opcode == BPF_JNE) &&
1309 regs[insn->dst_reg].type == CONST_IMM &&
1310 regs[insn->dst_reg].imm == insn->imm) {
1311 if (opcode == BPF_JEQ) {
1312 /* if (imm == imm) goto pc+off;
1313 * only follow the goto, ignore fall-through
1314 */
1315 *insn_idx += insn->off;
1316 return 0;
1317 } else {
1318 /* if (imm != imm) goto pc+off;
1319 * only follow fall-through branch, since
1320 * that's where the program will go
1321 */
1322 return 0;
1323 }
1324 }
1325
1326 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx);
1327 if (!other_branch)
1328 return -EFAULT;
1329
1330 /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */
1331 if (BPF_SRC(insn->code) == BPF_K &&
1332 insn->imm == 0 && (opcode == BPF_JEQ ||
1333 opcode == BPF_JNE) &&
1334 regs[insn->dst_reg].type == PTR_TO_MAP_VALUE_OR_NULL) {
1335 if (opcode == BPF_JEQ) {
1336 /* next fallthrough insn can access memory via
1337 * this register
1338 */
1339 regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1340 /* branch targer cannot access it, since reg == 0 */
1341 other_branch->regs[insn->dst_reg].type = CONST_IMM;
1342 other_branch->regs[insn->dst_reg].imm = 0;
1343 } else {
1344 other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE;
1345 regs[insn->dst_reg].type = CONST_IMM;
1346 regs[insn->dst_reg].imm = 0;
1347 }
1be7f75d
AS		 1348 } else if (is_pointer_value(env, insn->dst_reg)) {
1349 verbose("R%d pointer comparison prohibited\n", insn->dst_reg);
1350 return -EACCES;
17a52670
AS		 1351 } else if (BPF_SRC(insn->code) == BPF_K &&
1352 (opcode == BPF_JEQ || opcode == BPF_JNE)) {
1353
1354 if (opcode == BPF_JEQ) {
1355 /* detect if (R == imm) goto
1356 * and in the target state recognize that R = imm
1357 */
1358 other_branch->regs[insn->dst_reg].type = CONST_IMM;
1359 other_branch->regs[insn->dst_reg].imm = insn->imm;
1360 } else {
1361 /* detect if (R != imm) goto
1362 * and in the fall-through state recognize that R = imm
1363 */
1364 regs[insn->dst_reg].type = CONST_IMM;
1365 regs[insn->dst_reg].imm = insn->imm;
1366 }
1367 }
1368 if (log_level)
1369 print_verifier_state(env);
1370 return 0;
1371}
1372
0246e64d
AS		 1373/* return the map pointer stored inside BPF_LD_IMM64 instruction */
1374static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn)
1375{
1376 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32;
1377
1378 return (struct bpf_map *) (unsigned long) imm64;
1379}
1380
17a52670
AS		 1381/* verify BPF_LD_IMM64 instruction */
1382static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn)
1383{
1384 struct reg_state *regs = env->cur_state.regs;
1385 int err;
1386
1387 if (BPF_SIZE(insn->code) != BPF_DW) {
1388 verbose("invalid BPF_LD_IMM insn\n");
1389 return -EINVAL;
1390 }
1391 if (insn->off != 0) {
1392 verbose("BPF_LD_IMM64 uses reserved fields\n");
1393 return -EINVAL;
1394 }
1395
1396 err = check_reg_arg(regs, insn->dst_reg, DST_OP);
1397 if (err)
1398 return err;
1399
1400 if (insn->src_reg == 0)
1401 /* generic move 64-bit immediate into a register */
1402 return 0;
1403
1404 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
1405 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);
1406
1407 regs[insn->dst_reg].type = CONST_PTR_TO_MAP;
1408 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn);
1409 return 0;
1410}
1411
96be4325
DB		 1412static bool may_access_skb(enum bpf_prog_type type)
1413{
1414 switch (type) {
1415 case BPF_PROG_TYPE_SOCKET_FILTER:
1416 case BPF_PROG_TYPE_SCHED_CLS:
94caee8c 1417 case BPF_PROG_TYPE_SCHED_ACT:
96be4325
DB		 1418 return true;
1419 default:
1420 return false;
1421 }
1422}
1423
ddd872bc
AS		 1424/* verify safety of LD_ABS|LD_IND instructions:
1425 * - they can only appear in the programs where ctx == skb
1426 * - since they are wrappers of function calls, they scratch R1-R5 registers,
1427 * preserve R6-R9, and store return value into R0
1428 *
1429 * Implicit input:
1430 * ctx == skb == R6 == CTX
1431 *
1432 * Explicit input:
1433 * SRC == any register
1434 * IMM == 32-bit immediate
1435 *
1436 * Output:
1437 * R0 - 8/16/32-bit skb data converted to cpu endianness
1438 */
1439static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn)
1440{
1441 struct reg_state *regs = env->cur_state.regs;
1442 u8 mode = BPF_MODE(insn->code);
1443 struct reg_state *reg;
1444 int i, err;
1445
24701ece 1446 if (!may_access_skb(env->prog->type)) {
96be4325 1447 verbose("BPF_LD_ABS|IND instructions not allowed for this program type\n");
ddd872bc
AS		 1448 return -EINVAL;
1449 }
1450
1451 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
d82bccc6 1452 BPF_SIZE(insn->code) == BPF_DW ||
ddd872bc
AS		 1453 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
1454 verbose("BPF_LD_ABS uses reserved fields\n");
1455 return -EINVAL;
1456 }
1457
1458 /* check whether implicit source operand (register R6) is readable */
1459 err = check_reg_arg(regs, BPF_REG_6, SRC_OP);
1460 if (err)
1461 return err;
1462
1463 if (regs[BPF_REG_6].type != PTR_TO_CTX) {
1464 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
1465 return -EINVAL;
1466 }
1467
1468 if (mode == BPF_IND) {
1469 /* check explicit source operand */
1470 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1471 if (err)
1472 return err;
1473 }
1474
1475 /* reset caller saved regs to unreadable */
1476 for (i = 0; i < CALLER_SAVED_REGS; i++) {
1477 reg = regs + caller_saved[i];
1478 reg->type = NOT_INIT;
1479 reg->imm = 0;
1480 }
1481
1482 /* mark destination R0 register as readable, since it contains
1483 * the value fetched from the packet
1484 */
1485 regs[BPF_REG_0].type = UNKNOWN_VALUE;
1486 return 0;
1487}
1488
475fb78f
AS		 1489/* non-recursive DFS pseudo code
1490 * 1 procedure DFS-iterative(G,v):
1491 * 2 label v as discovered
1492 * 3 let S be a stack
1493 * 4 S.push(v)
1494 * 5 while S is not empty
1495 * 6 t <- S.pop()
1496 * 7 if t is what we're looking for:
1497 * 8 return t
1498 * 9 for all edges e in G.adjacentEdges(t) do
1499 * 10 if edge e is already labelled
1500 * 11 continue with the next edge
1501 * 12 w <- G.adjacentVertex(t,e)
1502 * 13 if vertex w is not discovered and not explored
1503 * 14 label e as tree-edge
1504 * 15 label w as discovered
1505 * 16 S.push(w)
1506 * 17 continue at 5
1507 * 18 else if vertex w is discovered
1508 * 19 label e as back-edge
1509 * 20 else
1510 * 21 // vertex w is explored
1511 * 22 label e as forward- or cross-edge
1512 * 23 label t as explored
1513 * 24 S.pop()
1514 *
1515 * convention:
1516 * 0x10 - discovered
1517 * 0x11 - discovered and fall-through edge labelled
1518 * 0x12 - discovered and fall-through and branch edges labelled
1519 * 0x20 - explored
1520 */
1521
1522enum {
1523 DISCOVERED = 0x10,
1524 EXPLORED = 0x20,
1525 FALLTHROUGH = 1,
1526 BRANCH = 2,
1527};
1528
f1bca824
AS		 1529#define STATE_LIST_MARK ((struct verifier_state_list *) -1L)
1530
475fb78f
AS		 1531static int *insn_stack; /* stack of insns to process */
1532static int cur_stack; /* current stack index */
1533static int *insn_state;
1534
1535/* t, w, e - match pseudo-code above:
1536 * t - index of current instruction
1537 * w - next instruction
1538 * e - edge
1539 */
1540static int push_insn(int t, int w, int e, struct verifier_env *env)
1541{
1542 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
1543 return 0;
1544
1545 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
1546 return 0;
1547
1548 if (w < 0 || w >= env->prog->len) {
1549 verbose("jump out of range from insn %d to %d\n", t, w);
1550 return -EINVAL;
1551 }
1552
f1bca824
AS		 1553 if (e == BRANCH)
1554 /* mark branch target for state pruning */
1555 env->explored_states[w] = STATE_LIST_MARK;
1556
475fb78f
AS		 1557 if (insn_state[w] == 0) {
1558 /* tree-edge */
1559 insn_state[t] = DISCOVERED | e;
1560 insn_state[w] = DISCOVERED;
1561 if (cur_stack >= env->prog->len)
1562 return -E2BIG;
1563 insn_stack[cur_stack++] = w;
1564 return 1;
1565 } else if ((insn_state[w] & 0xF0) == DISCOVERED) {
1566 verbose("back-edge from insn %d to %d\n", t, w);
1567 return -EINVAL;
1568 } else if (insn_state[w] == EXPLORED) {
1569 /* forward- or cross-edge */
1570 insn_state[t] = DISCOVERED | e;
1571 } else {
1572 verbose("insn state internal bug\n");
1573 return -EFAULT;
1574 }
1575 return 0;
1576}
1577
1578/* non-recursive depth-first-search to detect loops in BPF program
1579 * loop == back-edge in directed graph
1580 */
1581static int check_cfg(struct verifier_env *env)
1582{
1583 struct bpf_insn *insns = env->prog->insnsi;
1584 int insn_cnt = env->prog->len;
1585 int ret = 0;
1586 int i, t;
1587
1588 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1589 if (!insn_state)
1590 return -ENOMEM;
1591
1592 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
1593 if (!insn_stack) {
1594 kfree(insn_state);
1595 return -ENOMEM;
1596 }
1597
1598 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
1599 insn_stack[0] = 0; /* 0 is the first instruction */
1600 cur_stack = 1;
1601
1602peek_stack:
1603 if (cur_stack == 0)
1604 goto check_state;
1605 t = insn_stack[cur_stack - 1];
1606
1607 if (BPF_CLASS(insns[t].code) == BPF_JMP) {
1608 u8 opcode = BPF_OP(insns[t].code);
1609
1610 if (opcode == BPF_EXIT) {
1611 goto mark_explored;
1612 } else if (opcode == BPF_CALL) {
1613 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1614 if (ret == 1)
1615 goto peek_stack;
1616 else if (ret < 0)
1617 goto err_free;
07016151
DB		 1618 if (t + 1 < insn_cnt)
1619 env->explored_states[t + 1] = STATE_LIST_MARK;
475fb78f
AS		 1620 } else if (opcode == BPF_JA) {
1621 if (BPF_SRC(insns[t].code) != BPF_K) {
1622 ret = -EINVAL;
1623 goto err_free;
1624 }
1625 /* unconditional jump with single edge */
1626 ret = push_insn(t, t + insns[t].off + 1,
1627 FALLTHROUGH, env);
1628 if (ret == 1)
1629 goto peek_stack;
1630 else if (ret < 0)
1631 goto err_free;
f1bca824
AS		 1632 /* tell verifier to check for equivalent states
1633 * after every call and jump
1634 */
c3de6317
AS		 1635 if (t + 1 < insn_cnt)
1636 env->explored_states[t + 1] = STATE_LIST_MARK;
475fb78f
AS		 1637 } else {
1638 /* conditional jump with two edges */
1639 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1640 if (ret == 1)
1641 goto peek_stack;
1642 else if (ret < 0)
1643 goto err_free;
1644
1645 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
1646 if (ret == 1)
1647 goto peek_stack;
1648 else if (ret < 0)
1649 goto err_free;
1650 }
1651 } else {
1652 /* all other non-branch instructions with single
1653 * fall-through edge
1654 */
1655 ret = push_insn(t, t + 1, FALLTHROUGH, env);
1656 if (ret == 1)
1657 goto peek_stack;
1658 else if (ret < 0)
1659 goto err_free;
1660 }
1661
1662mark_explored:
1663 insn_state[t] = EXPLORED;
1664 if (cur_stack-- <= 0) {
1665 verbose("pop stack internal bug\n");
1666 ret = -EFAULT;
1667 goto err_free;
1668 }
1669 goto peek_stack;
1670
1671check_state:
1672 for (i = 0; i < insn_cnt; i++) {
1673 if (insn_state[i] != EXPLORED) {
1674 verbose("unreachable insn %d\n", i);
1675 ret = -EINVAL;
1676 goto err_free;
1677 }
1678 }
1679 ret = 0; /* cfg looks good */
1680
1681err_free:
1682 kfree(insn_state);
1683 kfree(insn_stack);
1684 return ret;
1685}
1686
f1bca824
AS		 1687/* compare two verifier states
1688 *
1689 * all states stored in state_list are known to be valid, since
1690 * verifier reached 'bpf_exit' instruction through them
1691 *
1692 * this function is called when verifier exploring different branches of
1693 * execution popped from the state stack. If it sees an old state that has
1694 * more strict register state and more strict stack state then this execution
1695 * branch doesn't need to be explored further, since verifier already
1696 * concluded that more strict state leads to valid finish.
1697 *
1698 * Therefore two states are equivalent if register state is more conservative
1699 * and explored stack state is more conservative than the current one.
1700 * Example:
1701 * explored current
1702 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
1703 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
1704 *
1705 * In other words if current stack state (one being explored) has more
1706 * valid slots than old one that already passed validation, it means
1707 * the verifier can stop exploring and conclude that current state is valid too
1708 *
1709 * Similarly with registers. If explored state has register type as invalid
1710 * whereas register type in current state is meaningful, it means that
1711 * the current state will reach 'bpf_exit' instruction safely
1712 */
1713static bool states_equal(struct verifier_state *old, struct verifier_state *cur)
1714{
1715 int i;
1716
1717 for (i = 0; i < MAX_BPF_REG; i++) {
1718 if (memcmp(&old->regs[i], &cur->regs[i],
1719 sizeof(old->regs[0])) != 0) {
1720 if (old->regs[i].type == NOT_INIT ||
32bf08a6
AS		 1721 (old->regs[i].type == UNKNOWN_VALUE &&
1722 cur->regs[i].type != NOT_INIT))
f1bca824
AS		 1723 continue;
1724 return false;
1725 }
1726 }
1727
1728 for (i = 0; i < MAX_BPF_STACK; i++) {
9c399760
AS		 1729 if (old->stack_slot_type[i] == STACK_INVALID)
1730 continue;
1731 if (old->stack_slot_type[i] != cur->stack_slot_type[i])
1732 /* Ex: old explored (safe) state has STACK_SPILL in
1733 * this stack slot, but current has has STACK_MISC ->
1734 * this verifier states are not equivalent,
1735 * return false to continue verification of this path
1736 */
f1bca824 1737 return false;
9c399760
AS		 1738 if (i % BPF_REG_SIZE)
1739 continue;
1740 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE],
1741 &cur->spilled_regs[i / BPF_REG_SIZE],
1742 sizeof(old->spilled_regs[0])))
1743 /* when explored and current stack slot types are
1744 * the same, check that stored pointers types
1745 * are the same as well.
1746 * Ex: explored safe path could have stored
1747 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8}
1748 * but current path has stored:
1749 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16}
1750 * such verifier states are not equivalent.
1751 * return false to continue verification of this path
1752 */
1753 return false;
1754 else
1755 continue;
f1bca824
AS		 1756 }
1757 return true;
1758}
1759
1760static int is_state_visited(struct verifier_env *env, int insn_idx)
1761{
1762 struct verifier_state_list *new_sl;
1763 struct verifier_state_list *sl;
1764
1765 sl = env->explored_states[insn_idx];
1766 if (!sl)
1767 /* this 'insn_idx' instruction wasn't marked, so we will not
1768 * be doing state search here
1769 */
1770 return 0;
1771
1772 while (sl != STATE_LIST_MARK) {
1773 if (states_equal(&sl->state, &env->cur_state))
1774 /* reached equivalent register/stack state,
1775 * prune the search
1776 */
1777 return 1;
1778 sl = sl->next;
1779 }
1780
1781 /* there were no equivalent states, remember current one.
1782 * technically the current state is not proven to be safe yet,
1783 * but it will either reach bpf_exit (which means it's safe) or
1784 * it will be rejected. Since there are no loops, we won't be
1785 * seeing this 'insn_idx' instruction again on the way to bpf_exit
1786 */
1787 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER);
1788 if (!new_sl)
1789 return -ENOMEM;
1790
1791 /* add new state to the head of linked list */
1792 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state));
1793 new_sl->next = env->explored_states[insn_idx];
1794 env->explored_states[insn_idx] = new_sl;
1795 return 0;
1796}
1797
17a52670
AS		 1798static int do_check(struct verifier_env *env)
1799{
1800 struct verifier_state *state = &env->cur_state;
1801 struct bpf_insn *insns = env->prog->insnsi;
1802 struct reg_state *regs = state->regs;
1803 int insn_cnt = env->prog->len;
1804 int insn_idx, prev_insn_idx = 0;
1805 int insn_processed = 0;
1806 bool do_print_state = false;
1807
1808 init_reg_state(regs);
1809 insn_idx = 0;
1810 for (;;) {
1811 struct bpf_insn *insn;
1812 u8 class;
1813 int err;
1814
1815 if (insn_idx >= insn_cnt) {
1816 verbose("invalid insn idx %d insn_cnt %d\n",
1817 insn_idx, insn_cnt);
1818 return -EFAULT;
1819 }
1820
1821 insn = &insns[insn_idx];
1822 class = BPF_CLASS(insn->code);
1823
07016151 1824 if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) {
17a52670
AS		 1825 verbose("BPF program is too large. Proccessed %d insn\n",
1826 insn_processed);
1827 return -E2BIG;
1828 }
1829
f1bca824
AS		 1830 err = is_state_visited(env, insn_idx);
1831 if (err < 0)
1832 return err;
1833 if (err == 1) {
1834 /* found equivalent state, can prune the search */
1835 if (log_level) {
1836 if (do_print_state)
1837 verbose("\nfrom %d to %d: safe\n",
1838 prev_insn_idx, insn_idx);
1839 else
1840 verbose("%d: safe\n", insn_idx);
1841 }
1842 goto process_bpf_exit;
1843 }
1844
17a52670
AS		 1845 if (log_level && do_print_state) {
1846 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx);
1847 print_verifier_state(env);
1848 do_print_state = false;
1849 }
1850
1851 if (log_level) {
1852 verbose("%d: ", insn_idx);
1853 print_bpf_insn(insn);
1854 }
1855
1856 if (class == BPF_ALU || class == BPF_ALU64) {
1be7f75d 1857 err = check_alu_op(env, insn);
17a52670
AS		 1858 if (err)
1859 return err;
1860
1861 } else if (class == BPF_LDX) {
9bac3d6d
AS		 1862 enum bpf_reg_type src_reg_type;
1863
1864 /* check for reserved fields is already done */
1865
17a52670
AS		 1866 /* check src operand */
1867 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1868 if (err)
1869 return err;
1870
1871 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
1872 if (err)
1873 return err;
1874
725f9dcd
AS		 1875 src_reg_type = regs[insn->src_reg].type;
1876
17a52670
AS		 1877 /* check that memory (src_reg + off) is readable,
1878 * the state of dst_reg will be updated by this func
1879 */
1880 err = check_mem_access(env, insn->src_reg, insn->off,
1881 BPF_SIZE(insn->code), BPF_READ,
1882 insn->dst_reg);
1883 if (err)
1884 return err;
1885
725f9dcd
AS		 1886 if (BPF_SIZE(insn->code) != BPF_W) {
1887 insn_idx++;
1888 continue;
1889 }
9bac3d6d 1890
725f9dcd 1891 if (insn->imm == 0) {
9bac3d6d
AS		 1892 /* saw a valid insn
1893 * dst_reg = *(u32 *)(src_reg + off)
1894 * use reserved 'imm' field to mark this insn
1895 */
1896 insn->imm = src_reg_type;
1897
1898 } else if (src_reg_type != insn->imm &&
1899 (src_reg_type == PTR_TO_CTX ||
1900 insn->imm == PTR_TO_CTX)) {
1901 /* ABuser program is trying to use the same insn
1902 * dst_reg = *(u32*) (src_reg + off)
1903 * with different pointer types:
1904 * src_reg == ctx in one branch and
1905 * src_reg == stack|map in some other branch.
1906 * Reject it.
1907 */
1908 verbose("same insn cannot be used with different pointers\n");
1909 return -EINVAL;
1910 }
1911
17a52670 1912 } else if (class == BPF_STX) {
d691f9e8
AS		 1913 enum bpf_reg_type dst_reg_type;
1914
17a52670
AS		 1915 if (BPF_MODE(insn->code) == BPF_XADD) {
1916 err = check_xadd(env, insn);
1917 if (err)
1918 return err;
1919 insn_idx++;
1920 continue;
1921 }
1922
17a52670
AS		 1923 /* check src1 operand */
1924 err = check_reg_arg(regs, insn->src_reg, SRC_OP);
1925 if (err)
1926 return err;
1927 /* check src2 operand */
1928 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1929 if (err)
1930 return err;
1931
d691f9e8
AS		 1932 dst_reg_type = regs[insn->dst_reg].type;
1933
17a52670
AS		 1934 /* check that memory (dst_reg + off) is writeable */
1935 err = check_mem_access(env, insn->dst_reg, insn->off,
1936 BPF_SIZE(insn->code), BPF_WRITE,
1937 insn->src_reg);
1938 if (err)
1939 return err;
1940
d691f9e8
AS		 1941 if (insn->imm == 0) {
1942 insn->imm = dst_reg_type;
1943 } else if (dst_reg_type != insn->imm &&
1944 (dst_reg_type == PTR_TO_CTX ||
1945 insn->imm == PTR_TO_CTX)) {
1946 verbose("same insn cannot be used with different pointers\n");
1947 return -EINVAL;
1948 }
1949
17a52670
AS		 1950 } else if (class == BPF_ST) {
1951 if (BPF_MODE(insn->code) != BPF_MEM ||
1952 insn->src_reg != BPF_REG_0) {
1953 verbose("BPF_ST uses reserved fields\n");
1954 return -EINVAL;
1955 }
1956 /* check src operand */
1957 err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
1958 if (err)
1959 return err;
1960
1961 /* check that memory (dst_reg + off) is writeable */
1962 err = check_mem_access(env, insn->dst_reg, insn->off,
1963 BPF_SIZE(insn->code), BPF_WRITE,
1964 -1);
1965 if (err)
1966 return err;
1967
1968 } else if (class == BPF_JMP) {
1969 u8 opcode = BPF_OP(insn->code);
1970
1971 if (opcode == BPF_CALL) {
1972 if (BPF_SRC(insn->code) != BPF_K ||
1973 insn->off != 0 ||
1974 insn->src_reg != BPF_REG_0 ||
1975 insn->dst_reg != BPF_REG_0) {
1976 verbose("BPF_CALL uses reserved fields\n");
1977 return -EINVAL;
1978 }
1979
1980 err = check_call(env, insn->imm);
1981 if (err)
1982 return err;
1983
1984 } else if (opcode == BPF_JA) {
1985 if (BPF_SRC(insn->code) != BPF_K ||
1986 insn->imm != 0 ||
1987 insn->src_reg != BPF_REG_0 ||
1988 insn->dst_reg != BPF_REG_0) {
1989 verbose("BPF_JA uses reserved fields\n");
1990 return -EINVAL;
1991 }
1992
1993 insn_idx += insn->off + 1;
1994 continue;
1995
1996 } else if (opcode == BPF_EXIT) {
1997 if (BPF_SRC(insn->code) != BPF_K ||
1998 insn->imm != 0 ||
1999 insn->src_reg != BPF_REG_0 ||
2000 insn->dst_reg != BPF_REG_0) {
2001 verbose("BPF_EXIT uses reserved fields\n");
2002 return -EINVAL;
2003 }
2004
2005 /* eBPF calling convetion is such that R0 is used
2006 * to return the value from eBPF program.
2007 * Make sure that it's readable at this time
2008 * of bpf_exit, which means that program wrote
2009 * something into it earlier
2010 */
2011 err = check_reg_arg(regs, BPF_REG_0, SRC_OP);
2012 if (err)
2013 return err;
2014
1be7f75d
AS		 2015 if (is_pointer_value(env, BPF_REG_0)) {
2016 verbose("R0 leaks addr as return value\n");
2017 return -EACCES;
2018 }
2019
f1bca824 2020process_bpf_exit:
17a52670
AS		 2021 insn_idx = pop_stack(env, &prev_insn_idx);
2022 if (insn_idx < 0) {
2023 break;
2024 } else {
2025 do_print_state = true;
2026 continue;
2027 }
2028 } else {
2029 err = check_cond_jmp_op(env, insn, &insn_idx);
2030 if (err)
2031 return err;
2032 }
2033 } else if (class == BPF_LD) {
2034 u8 mode = BPF_MODE(insn->code);
2035
2036 if (mode == BPF_ABS || mode == BPF_IND) {
ddd872bc
AS		 2037 err = check_ld_abs(env, insn);
2038 if (err)
2039 return err;
2040
17a52670
AS		 2041 } else if (mode == BPF_IMM) {
2042 err = check_ld_imm(env, insn);
2043 if (err)
2044 return err;
2045
2046 insn_idx++;
2047 } else {
2048 verbose("invalid BPF_LD mode\n");
2049 return -EINVAL;
2050 }
2051 } else {
2052 verbose("unknown insn class %d\n", class);
2053 return -EINVAL;
2054 }
2055
2056 insn_idx++;
2057 }
2058
2059 return 0;
2060}
2061
0246e64d
AS		 2062/* look for pseudo eBPF instructions that access map FDs and
2063 * replace them with actual map pointers
2064 */
2065static int replace_map_fd_with_map_ptr(struct verifier_env *env)
2066{
2067 struct bpf_insn *insn = env->prog->insnsi;
2068 int insn_cnt = env->prog->len;
2069 int i, j;
2070
2071 for (i = 0; i < insn_cnt; i++, insn++) {
9bac3d6d 2072 if (BPF_CLASS(insn->code) == BPF_LDX &&
d691f9e8 2073 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
9bac3d6d
AS		 2074 verbose("BPF_LDX uses reserved fields\n");
2075 return -EINVAL;
2076 }
2077
d691f9e8
AS		 2078 if (BPF_CLASS(insn->code) == BPF_STX &&
2079 ((BPF_MODE(insn->code) != BPF_MEM &&
2080 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
2081 verbose("BPF_STX uses reserved fields\n");
2082 return -EINVAL;
2083 }
2084
0246e64d
AS		 2085 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
2086 struct bpf_map *map;
2087 struct fd f;
2088
2089 if (i == insn_cnt - 1 || insn[1].code != 0 ||
2090 insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
2091 insn[1].off != 0) {
2092 verbose("invalid bpf_ld_imm64 insn\n");
2093 return -EINVAL;
2094 }
2095
2096 if (insn->src_reg == 0)
2097 /* valid generic load 64-bit imm */
2098 goto next_insn;
2099
2100 if (insn->src_reg != BPF_PSEUDO_MAP_FD) {
2101 verbose("unrecognized bpf_ld_imm64 insn\n");
2102 return -EINVAL;
2103 }
2104
2105 f = fdget(insn->imm);
c2101297 2106 map = __bpf_map_get(f);
0246e64d
AS		 2107 if (IS_ERR(map)) {
2108 verbose("fd %d is not pointing to valid bpf_map\n",
2109 insn->imm);
0246e64d
AS		 2110 return PTR_ERR(map);
2111 }
2112
2113 /* store map pointer inside BPF_LD_IMM64 instruction */
2114 insn[0].imm = (u32) (unsigned long) map;
2115 insn[1].imm = ((u64) (unsigned long) map) >> 32;
2116
2117 /* check whether we recorded this map already */
2118 for (j = 0; j < env->used_map_cnt; j++)
2119 if (env->used_maps[j] == map) {
2120 fdput(f);
2121 goto next_insn;
2122 }
2123
2124 if (env->used_map_cnt >= MAX_USED_MAPS) {
2125 fdput(f);
2126 return -E2BIG;
2127 }
2128
0246e64d
AS		 2129 /* hold the map. If the program is rejected by verifier,
2130 * the map will be released by release_maps() or it
2131 * will be used by the valid program until it's unloaded
2132 * and all maps are released in free_bpf_prog_info()
2133 */
92117d84
AS		 2134 map = bpf_map_inc(map, false);
2135 if (IS_ERR(map)) {
2136 fdput(f);
2137 return PTR_ERR(map);
2138 }
2139 env->used_maps[env->used_map_cnt++] = map;
2140
0246e64d
AS		 2141 fdput(f);
2142next_insn:
2143 insn++;
2144 i++;
2145 }
2146 }
2147
2148 /* now all pseudo BPF_LD_IMM64 instructions load valid
2149 * 'struct bpf_map *' into a register instead of user map_fd.
2150 * These pointers will be used later by verifier to validate map access.
2151 */
2152 return 0;
2153}
2154
2155/* drop refcnt of maps used by the rejected program */
2156static void release_maps(struct verifier_env *env)
2157{
2158 int i;
2159
2160 for (i = 0; i < env->used_map_cnt; i++)
2161 bpf_map_put(env->used_maps[i]);
2162}
2163
2164/* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
2165static void convert_pseudo_ld_imm64(struct verifier_env *env)
2166{
2167 struct bpf_insn *insn = env->prog->insnsi;
2168 int insn_cnt = env->prog->len;
2169 int i;
2170
2171 for (i = 0; i < insn_cnt; i++, insn++)
2172 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW))
2173 insn->src_reg = 0;
2174}
2175
9bac3d6d
AS		 2176static void adjust_branches(struct bpf_prog *prog, int pos, int delta)
2177{
2178 struct bpf_insn *insn = prog->insnsi;
2179 int insn_cnt = prog->len;
2180 int i;
2181
2182 for (i = 0; i < insn_cnt; i++, insn++) {
2183 if (BPF_CLASS(insn->code) != BPF_JMP ||
2184 BPF_OP(insn->code) == BPF_CALL ||
2185 BPF_OP(insn->code) == BPF_EXIT)
2186 continue;
2187
2188 /* adjust offset of jmps if necessary */
2189 if (i < pos && i + insn->off + 1 > pos)
2190 insn->off += delta;
a1b14d27 2191 else if (i > pos + delta && i + insn->off + 1 <= pos + delta)
9bac3d6d
AS		 2192 insn->off -= delta;
2193 }
2194}
2195
2196/* convert load instructions that access fields of 'struct __sk_buff'
2197 * into sequence of instructions that access fields of 'struct sk_buff'
2198 */
2199static int convert_ctx_accesses(struct verifier_env *env)
2200{
2201 struct bpf_insn *insn = env->prog->insnsi;
2202 int insn_cnt = env->prog->len;
2203 struct bpf_insn insn_buf[16];
2204 struct bpf_prog *new_prog;
2205 u32 cnt;
2206 int i;
d691f9e8 2207 enum bpf_access_type type;
9bac3d6d
AS		 2208
2209 if (!env->prog->aux->ops->convert_ctx_access)
2210 return 0;
2211
2212 for (i = 0; i < insn_cnt; i++, insn++) {
d691f9e8
AS		 2213 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
2214 type = BPF_READ;
2215 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
2216 type = BPF_WRITE;
2217 else
9bac3d6d
AS		 2218 continue;
2219
2220 if (insn->imm != PTR_TO_CTX) {
2221 /* clear internal mark */
2222 insn->imm = 0;
2223 continue;
2224 }
2225
2226 cnt = env->prog->aux->ops->
d691f9e8 2227 convert_ctx_access(type, insn->dst_reg, insn->src_reg,
ff936a04 2228 insn->off, insn_buf, env->prog);
9bac3d6d
AS		 2229 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
2230 verbose("bpf verifier is misconfigured\n");
2231 return -EINVAL;
2232 }
2233
2234 if (cnt == 1) {
2235 memcpy(insn, insn_buf, sizeof(*insn));
2236 continue;
2237 }
2238
2239 /* several new insns need to be inserted. Make room for them */
2240 insn_cnt += cnt - 1;
2241 new_prog = bpf_prog_realloc(env->prog,
2242 bpf_prog_size(insn_cnt),
2243 GFP_USER);
2244 if (!new_prog)
2245 return -ENOMEM;
2246
2247 new_prog->len = insn_cnt;
2248
2249 memmove(new_prog->insnsi + i + cnt, new_prog->insns + i + 1,
2250 sizeof(*insn) * (insn_cnt - i - cnt));
2251
2252 /* copy substitute insns in place of load instruction */
2253 memcpy(new_prog->insnsi + i, insn_buf, sizeof(*insn) * cnt);
2254
2255 /* adjust branches in the whole program */
2256 adjust_branches(new_prog, i, cnt - 1);
2257
2258 /* keep walking new program and skip insns we just inserted */
2259 env->prog = new_prog;
2260 insn = new_prog->insnsi + i + cnt - 1;
2261 i += cnt - 1;
2262 }
2263
2264 return 0;
2265}
2266
f1bca824
AS		 2267static void free_states(struct verifier_env *env)
2268{
2269 struct verifier_state_list *sl, *sln;
2270 int i;
2271
2272 if (!env->explored_states)
2273 return;
2274
2275 for (i = 0; i < env->prog->len; i++) {
2276 sl = env->explored_states[i];
2277
2278 if (sl)
2279 while (sl != STATE_LIST_MARK) {
2280 sln = sl->next;
2281 kfree(sl);
2282 sl = sln;
2283 }
2284 }
2285
2286 kfree(env->explored_states);
2287}
2288
9bac3d6d 2289int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
51580e79 2290{
cbd35700
AS		 2291 char __user *log_ubuf = NULL;
2292 struct verifier_env *env;
51580e79
AS		 2293 int ret = -EINVAL;
2294
9bac3d6d 2295 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS)
cbd35700
AS		 2296 return -E2BIG;
2297
2298 /* 'struct verifier_env' can be global, but since it's not small,
2299 * allocate/free it every time bpf_check() is called
2300 */
2301 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL);
2302 if (!env)
2303 return -ENOMEM;
2304
9bac3d6d 2305 env->prog = *prog;
0246e64d 2306
cbd35700
AS		 2307 /* grab the mutex to protect few globals used by verifier */
2308 mutex_lock(&bpf_verifier_lock);
2309
2310 if (attr->log_level || attr->log_buf || attr->log_size) {
2311 /* user requested verbose verifier output
2312 * and supplied buffer to store the verification trace
2313 */
2314 log_level = attr->log_level;
2315 log_ubuf = (char __user *) (unsigned long) attr->log_buf;
2316 log_size = attr->log_size;
2317 log_len = 0;
2318
2319 ret = -EINVAL;
2320 /* log_* values have to be sane */
2321 if (log_size < 128 || log_size > UINT_MAX >> 8 ||
2322 log_level == 0 || log_ubuf == NULL)
2323 goto free_env;
2324
2325 ret = -ENOMEM;
2326 log_buf = vmalloc(log_size);
2327 if (!log_buf)
2328 goto free_env;
2329 } else {
2330 log_level = 0;
2331 }
2332
0246e64d
AS		 2333 ret = replace_map_fd_with_map_ptr(env);
2334 if (ret < 0)
2335 goto skip_full_check;
2336
9bac3d6d 2337 env->explored_states = kcalloc(env->prog->len,
f1bca824
AS		 2338 sizeof(struct verifier_state_list *),
2339 GFP_USER);
2340 ret = -ENOMEM;
2341 if (!env->explored_states)
2342 goto skip_full_check;
2343
475fb78f
AS		 2344 ret = check_cfg(env);
2345 if (ret < 0)
2346 goto skip_full_check;
2347
1be7f75d
AS		 2348 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN);
2349
17a52670 2350 ret = do_check(env);
cbd35700 2351
0246e64d 2352skip_full_check:
17a52670 2353 while (pop_stack(env, NULL) >= 0);
f1bca824 2354 free_states(env);
0246e64d 2355
9bac3d6d
AS		 2356 if (ret == 0)
2357 /* program is valid, convert *(u32*)(ctx + off) accesses */
2358 ret = convert_ctx_accesses(env);
2359
cbd35700
AS		 2360 if (log_level && log_len >= log_size - 1) {
2361 BUG_ON(log_len >= log_size);
2362 /* verifier log exceeded user supplied buffer */
2363 ret = -ENOSPC;
2364 /* fall through to return what was recorded */
2365 }
2366
2367 /* copy verifier log back to user space including trailing zero */
2368 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) {
2369 ret = -EFAULT;
2370 goto free_log_buf;
2371 }
2372
0246e64d
AS		 2373 if (ret == 0 && env->used_map_cnt) {
2374 /* if program passed verifier, update used_maps in bpf_prog_info */
9bac3d6d
AS		 2375 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
2376 sizeof(env->used_maps[0]),
2377 GFP_KERNEL);
0246e64d 2378
9bac3d6d 2379 if (!env->prog->aux->used_maps) {
0246e64d
AS		 2380 ret = -ENOMEM;
2381 goto free_log_buf;
2382 }
2383
9bac3d6d 2384 memcpy(env->prog->aux->used_maps, env->used_maps,
0246e64d 2385 sizeof(env->used_maps[0]) * env->used_map_cnt);
9bac3d6d 2386 env->prog->aux->used_map_cnt = env->used_map_cnt;
0246e64d
AS		 2387
2388 /* program is valid. Convert pseudo bpf_ld_imm64 into generic
2389 * bpf_ld_imm64 instructions
2390 */
2391 convert_pseudo_ld_imm64(env);
2392 }
cbd35700
AS		 2393
2394free_log_buf:
2395 if (log_level)
2396 vfree(log_buf);
2397free_env:
9bac3d6d 2398 if (!env->prog->aux->used_maps)
0246e64d
AS		 2399 /* if we didn't copy map pointers into bpf_prog_info, release
2400 * them now. Otherwise free_bpf_prog_info() will release them.
2401 */
2402 release_maps(env);
9bac3d6d 2403 *prog = env->prog;
cbd35700
AS		 2404 kfree(env);
2405 mutex_unlock(&bpf_verifier_lock);
51580e79
AS		 2406 return ret;
2407}
Linux kernel - Deliverables
This page took 0.202231 seconds and 5 git commands to generate.