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0ce20dd8 AP |
1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | /* | |
3 | * Kernel Electric-Fence (KFENCE). For more info please see | |
4 | * Documentation/dev-tools/kfence.rst. | |
5 | * | |
6 | * Copyright (C) 2020, Google LLC. | |
7 | */ | |
8 | ||
9 | #ifndef MM_KFENCE_KFENCE_H | |
10 | #define MM_KFENCE_KFENCE_H | |
11 | ||
12 | #include <linux/mm.h> | |
13 | #include <linux/slab.h> | |
14 | #include <linux/spinlock.h> | |
15 | #include <linux/types.h> | |
16 | ||
17 | #include "../slab.h" /* for struct kmem_cache */ | |
18 | ||
0ce20dd8 AP |
19 | /* |
20 | * Get the canary byte pattern for @addr. Use a pattern that varies based on the | |
21 | * lower 3 bits of the address, to detect memory corruptions with higher | |
22 | * probability, where similar constants are used. | |
23 | */ | |
1ba3cbf3 PZ |
24 | #define KFENCE_CANARY_PATTERN_U8(addr) ((u8)0xaa ^ (u8)((unsigned long)(addr) & 0x7)) |
25 | ||
26 | /* | |
27 | * Define a continuous 8-byte canary starting from a multiple of 8. The canary | |
28 | * of each byte is only related to the lowest three bits of its address, so the | |
29 | * canary of every 8 bytes is the same. 64-bit memory can be filled and checked | |
30 | * at a time instead of byte by byte to improve performance. | |
31 | */ | |
7581495a | 32 | #define KFENCE_CANARY_PATTERN_U64 ((u64)0xaaaaaaaaaaaaaaaa ^ (u64)(le64_to_cpu(0x0706050403020100))) |
0ce20dd8 AP |
33 | |
34 | /* Maximum stack depth for reports. */ | |
35 | #define KFENCE_STACK_DEPTH 64 | |
36 | ||
37 | /* KFENCE object states. */ | |
38 | enum kfence_object_state { | |
39 | KFENCE_OBJECT_UNUSED, /* Object is unused. */ | |
40 | KFENCE_OBJECT_ALLOCATED, /* Object is currently allocated. */ | |
41 | KFENCE_OBJECT_FREED, /* Object was allocated, and then freed. */ | |
42 | }; | |
43 | ||
44 | /* Alloc/free tracking information. */ | |
45 | struct kfence_track { | |
46 | pid_t pid; | |
4bbf04aa ME |
47 | int cpu; |
48 | u64 ts_nsec; | |
0ce20dd8 AP |
49 | int num_stack_entries; |
50 | unsigned long stack_entries[KFENCE_STACK_DEPTH]; | |
51 | }; | |
52 | ||
53 | /* KFENCE metadata per guarded allocation. */ | |
54 | struct kfence_metadata { | |
55 | struct list_head list; /* Freelist node; access under kfence_freelist_lock. */ | |
56 | struct rcu_head rcu_head; /* For delayed freeing. */ | |
57 | ||
58 | /* | |
59 | * Lock protecting below data; to ensure consistency of the below data, | |
60 | * since the following may execute concurrently: __kfence_alloc(), | |
61 | * __kfence_free(), kfence_handle_page_fault(). However, note that we | |
62 | * cannot grab the same metadata off the freelist twice, and multiple | |
63 | * __kfence_alloc() cannot run concurrently on the same metadata. | |
64 | */ | |
65 | raw_spinlock_t lock; | |
66 | ||
67 | /* The current state of the object; see above. */ | |
68 | enum kfence_object_state state; | |
69 | ||
70 | /* | |
71 | * Allocated object address; cannot be calculated from size, because of | |
72 | * alignment requirements. | |
73 | * | |
74 | * Invariant: ALIGN_DOWN(addr, PAGE_SIZE) is constant. | |
75 | */ | |
76 | unsigned long addr; | |
77 | ||
78 | /* | |
79 | * The size of the original allocation. | |
80 | */ | |
81 | size_t size; | |
82 | ||
83 | /* | |
84 | * The kmem_cache cache of the last allocation; NULL if never allocated | |
85 | * or the cache has already been destroyed. | |
86 | */ | |
87 | struct kmem_cache *cache; | |
88 | ||
89 | /* | |
90 | * In case of an invalid access, the page that was unprotected; we | |
91 | * optimistically only store one address. | |
92 | */ | |
93 | unsigned long unprotected_page; | |
94 | ||
95 | /* Allocation and free stack information. */ | |
96 | struct kfence_track alloc_track; | |
97 | struct kfence_track free_track; | |
08f6b106 ME |
98 | /* For updating alloc_covered on frees. */ |
99 | u32 alloc_stack_hash; | |
8f0b3649 MS |
100 | #ifdef CONFIG_MEMCG |
101 | struct obj_cgroup *objcg; | |
102 | #endif | |
0ce20dd8 AP |
103 | }; |
104 | ||
cabdf74e PZ |
105 | #define KFENCE_METADATA_SIZE PAGE_ALIGN(sizeof(struct kfence_metadata) * \ |
106 | CONFIG_KFENCE_NUM_OBJECTS) | |
107 | ||
108 | extern struct kfence_metadata *kfence_metadata; | |
0ce20dd8 | 109 | |
2dfe63e6 ME |
110 | static inline struct kfence_metadata *addr_to_metadata(unsigned long addr) |
111 | { | |
112 | long index; | |
113 | ||
114 | /* The checks do not affect performance; only called from slow-paths. */ | |
115 | ||
116 | if (!is_kfence_address((void *)addr)) | |
117 | return NULL; | |
118 | ||
119 | /* | |
120 | * May be an invalid index if called with an address at the edge of | |
121 | * __kfence_pool, in which case we would report an "invalid access" | |
122 | * error. | |
123 | */ | |
124 | index = (addr - (unsigned long)__kfence_pool) / (PAGE_SIZE * 2) - 1; | |
125 | if (index < 0 || index >= CONFIG_KFENCE_NUM_OBJECTS) | |
126 | return NULL; | |
127 | ||
128 | return &kfence_metadata[index]; | |
129 | } | |
130 | ||
0ce20dd8 AP |
131 | /* KFENCE error types for report generation. */ |
132 | enum kfence_error_type { | |
133 | KFENCE_ERROR_OOB, /* Detected a out-of-bounds access. */ | |
134 | KFENCE_ERROR_UAF, /* Detected a use-after-free access. */ | |
135 | KFENCE_ERROR_CORRUPTION, /* Detected a memory corruption on free. */ | |
136 | KFENCE_ERROR_INVALID, /* Invalid access of unknown type. */ | |
137 | KFENCE_ERROR_INVALID_FREE, /* Invalid free. */ | |
138 | }; | |
139 | ||
bc8fbc5f | 140 | void kfence_report_error(unsigned long address, bool is_write, struct pt_regs *regs, |
d438fabc | 141 | const struct kfence_metadata *meta, enum kfence_error_type type); |
0ce20dd8 AP |
142 | |
143 | void kfence_print_object(struct seq_file *seq, const struct kfence_metadata *meta); | |
144 | ||
145 | #endif /* MM_KFENCE_KFENCE_H */ |