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Jakub Kicinski58e2af82016-09-21 11:43:57 +01001/* 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#ifndef _LINUX_BPF_VERIFIER_H
8#define _LINUX_BPF_VERIFIER_H 1
9
10#include <linux/bpf.h> /* for enum bpf_reg_type */
11#include <linux/filter.h> /* for MAX_BPF_STACK */
Edward Creef1174f72017-08-07 15:26:19 +010012#include <linux/tnum.h>
Jakub Kicinski58e2af82016-09-21 11:43:57 +010013
Edward Creeb03c9f92017-08-07 15:26:36 +010014/* Maximum variable offset umax_value permitted when resolving memory accesses.
15 * In practice this is far bigger than any realistic pointer offset; this limit
16 * ensures that umax_value + (int)off + (int)size cannot overflow a u64.
17 */
Daniel Borkmannde317962017-12-22 16:23:11 +010018#define BPF_MAX_VAR_OFF (1 << 29)
Edward Creeb03c9f92017-08-07 15:26:36 +010019/* Maximum variable size permitted for ARG_CONST_SIZE[_OR_ZERO]. This ensures
20 * that converting umax_value to int cannot overflow.
21 */
Daniel Borkmannde317962017-12-22 16:23:11 +010022#define BPF_MAX_VAR_SIZ (1 << 29)
Josef Bacik48461132016-09-28 10:54:32 -040023
Edward Cree8e9cd9c2017-08-23 15:11:21 +010024/* Liveness marks, used for registers and spilled-regs (in stack slots).
25 * Read marks propagate upwards until they find a write mark; they record that
26 * "one of this state's descendants read this reg" (and therefore the reg is
27 * relevant for states_equal() checks).
28 * Write marks collect downwards and do not propagate; they record that "the
29 * straight-line code that reached this state (from its parent) wrote this reg"
30 * (and therefore that reads propagated from this state or its descendants
31 * should not propagate to its parent).
32 * A state with a write mark can receive read marks; it just won't propagate
33 * them to its parent, since the write mark is a property, not of the state,
34 * but of the link between it and its parent. See mark_reg_read() and
35 * mark_stack_slot_read() in kernel/bpf/verifier.c.
36 */
Edward Creedc503a82017-08-15 20:34:35 +010037enum bpf_reg_liveness {
38 REG_LIVE_NONE = 0, /* reg hasn't been read or written this branch */
39 REG_LIVE_READ, /* reg was read, so we're sensitive to initial value */
40 REG_LIVE_WRITTEN, /* reg was written first, screening off later reads */
41};
42
Jakub Kicinski58e2af82016-09-21 11:43:57 +010043struct bpf_reg_state {
44 enum bpf_reg_type type;
45 union {
Edward Creef1174f72017-08-07 15:26:19 +010046 /* valid when type == PTR_TO_PACKET */
47 u16 range;
Jakub Kicinski58e2af82016-09-21 11:43:57 +010048
49 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
50 * PTR_TO_MAP_VALUE_OR_NULL
51 */
52 struct bpf_map *map_ptr;
Daniel Borkmanneb9b1952018-11-01 22:30:38 +010053
54 /* Max size from any of the above. */
55 unsigned long raw;
Jakub Kicinski58e2af82016-09-21 11:43:57 +010056 };
Edward Creef1174f72017-08-07 15:26:19 +010057 /* Fixed part of pointer offset, pointer types only */
58 s32 off;
59 /* For PTR_TO_PACKET, used to find other pointers with the same variable
60 * offset, so they can share range knowledge.
61 * For PTR_TO_MAP_VALUE_OR_NULL this is used to share which map value we
62 * came from, when one is tested for != NULL.
63 */
Alexei Starovoitovd2a4dd32016-12-07 10:57:59 -080064 u32 id;
Edward Creedc503a82017-08-15 20:34:35 +010065 /* Ordering of fields matters. See states_equal() */
Edward Creef1174f72017-08-07 15:26:19 +010066 /* For scalar types (SCALAR_VALUE), this represents our knowledge of
67 * the actual value.
68 * For pointer types, this represents the variable part of the offset
69 * from the pointed-to object, and is shared with all bpf_reg_states
70 * with the same id as us.
71 */
72 struct tnum var_off;
Alexei Starovoitovd2a4dd32016-12-07 10:57:59 -080073 /* Used to determine if any memory access using this register will
Edward Creef1174f72017-08-07 15:26:19 +010074 * result in a bad access.
75 * These refer to the same value as var_off, not necessarily the actual
76 * contents of the register.
Alexei Starovoitovd2a4dd32016-12-07 10:57:59 -080077 */
Edward Creeb03c9f92017-08-07 15:26:36 +010078 s64 smin_value; /* minimum possible (s64)value */
79 s64 smax_value; /* maximum possible (s64)value */
80 u64 umin_value; /* minimum possible (u64)value */
81 u64 umax_value; /* maximum possible (u64)value */
Edward Creedc503a82017-08-15 20:34:35 +010082 /* This field must be last, for states_equal() reasons. */
83 enum bpf_reg_liveness live;
Jakub Kicinski58e2af82016-09-21 11:43:57 +010084};
85
86enum bpf_stack_slot_type {
87 STACK_INVALID, /* nothing was stored in this stack slot */
88 STACK_SPILL, /* register spilled into stack */
89 STACK_MISC /* BPF program wrote some data into this slot */
90};
91
92#define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
93
Alexei Starovoitov28356c22019-04-03 18:39:01 +000094struct bpf_stack_state {
95 struct bpf_reg_state spilled_ptr;
96 u8 slot_type[BPF_REG_SIZE];
97};
98
Jakub Kicinski58e2af82016-09-21 11:43:57 +010099/* state of the program:
100 * type of all registers and stack info
101 */
102struct bpf_verifier_state {
103 struct bpf_reg_state regs[MAX_BPF_REG];
Edward Creedc503a82017-08-15 20:34:35 +0100104 struct bpf_verifier_state *parent;
Alexei Starovoitov28356c22019-04-03 18:39:01 +0000105 int allocated_stack;
106 struct bpf_stack_state *stack;
Daniel Borkmannae03b6b2019-04-03 18:39:12 +0000107 bool speculative;
Jakub Kicinski58e2af82016-09-21 11:43:57 +0100108};
109
110/* linked list of verifier states used to prune search */
111struct bpf_verifier_state_list {
112 struct bpf_verifier_state state;
113 struct bpf_verifier_state_list *next;
114};
115
Daniel Borkmannae03b6b2019-04-03 18:39:12 +0000116/* Possible states for alu_state member. */
Daniel Borkmann19e4f402021-05-31 18:25:53 +0000117#define BPF_ALU_SANITIZE_SRC (1U << 0)
118#define BPF_ALU_SANITIZE_DST (1U << 1)
Daniel Borkmannae03b6b2019-04-03 18:39:12 +0000119#define BPF_ALU_NEG_VALUE (1U << 2)
Daniel Borkmann6588a492019-04-03 18:39:13 +0000120#define BPF_ALU_NON_POINTER (1U << 3)
Daniel Borkmann19e4f402021-05-31 18:25:53 +0000121#define BPF_ALU_IMMEDIATE (1U << 4)
Daniel Borkmannae03b6b2019-04-03 18:39:12 +0000122#define BPF_ALU_SANITIZE (BPF_ALU_SANITIZE_SRC | \
123 BPF_ALU_SANITIZE_DST)
124
Jakub Kicinski58e2af82016-09-21 11:43:57 +0100125struct bpf_insn_aux_data {
Alexei Starovoitov81ed18a2017-03-15 18:26:42 -0700126 union {
127 enum bpf_reg_type ptr_type; /* pointer type for load/store insns */
128 struct bpf_map *map_ptr; /* pointer for call insn into lookup_elem */
Daniel Borkmannae03b6b2019-04-03 18:39:12 +0000129 u32 alu_limit; /* limit for add/sub register with pointer */
Alexei Starovoitov81ed18a2017-03-15 18:26:42 -0700130 };
Yonghong Song23994632017-06-22 15:07:39 -0700131 int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
Alexei Starovoitov83b570c2018-05-15 09:27:05 -0700132 int sanitize_stack_off; /* stack slot to be cleared */
Daniel Borkmann2b3ea8c2017-12-22 16:22:59 +0100133 bool seen; /* this insn was processed by the verifier */
Daniel Borkmannae03b6b2019-04-03 18:39:12 +0000134 u8 alu_state; /* used in combination with alu_limit */
Jakub Kicinski58e2af82016-09-21 11:43:57 +0100135};
136
137#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
138
Jakub Kicinski13a27df2016-09-21 11:43:58 +0100139struct bpf_verifier_env;
140struct bpf_ext_analyzer_ops {
141 int (*insn_hook)(struct bpf_verifier_env *env,
142 int insn_idx, int prev_insn_idx);
143};
144
Jakub Kicinski58e2af82016-09-21 11:43:57 +0100145/* single container for all structs
146 * one verifier_env per bpf_check() call
147 */
148struct bpf_verifier_env {
Daniel Borkmann6a42c492019-04-03 18:39:05 +0000149 u32 insn_idx;
150 u32 prev_insn_idx;
Jakub Kicinski58e2af82016-09-21 11:43:57 +0100151 struct bpf_prog *prog; /* eBPF program being verified */
152 struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
153 int stack_size; /* number of states to be processed */
David S. Millere07b98d2017-05-10 11:38:07 -0700154 bool strict_alignment; /* perform strict pointer alignment checks */
Alexei Starovoitov28356c22019-04-03 18:39:01 +0000155 struct bpf_verifier_state *cur_state; /* current verifier state */
Jakub Kicinski58e2af82016-09-21 11:43:57 +0100156 struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
Jakub Kicinski13a27df2016-09-21 11:43:58 +0100157 const struct bpf_ext_analyzer_ops *analyzer_ops; /* external analyzer ops */
158 void *analyzer_priv; /* pointer to external analyzer's private data */
Jakub Kicinski58e2af82016-09-21 11:43:57 +0100159 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
160 u32 used_map_cnt; /* number of used maps */
161 u32 id_gen; /* used to generate unique reg IDs */
162 bool allow_ptr_leaks;
163 bool seen_direct_write;
164 struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
165};
166
Alexei Starovoitov28356c22019-04-03 18:39:01 +0000167static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env)
168{
169 return env->cur_state->regs;
170}
171
Jakub Kicinski13a27df2016-09-21 11:43:58 +0100172int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops,
173 void *priv);
174
Jakub Kicinski58e2af82016-09-21 11:43:57 +0100175#endif /* _LINUX_BPF_VERIFIER_H */