1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * Functions used by the KMSAN runtime.
4 *
5 * Copyright (C) 2017-2022 Google LLC
6 * Author: Alexander Potapenko <glider@google.com>
7 *
8 */
9
10 #ifndef __MM_KMSAN_KMSAN_H
11 #define __MM_KMSAN_KMSAN_H
12
13 #include <asm/pgtable_64_types.h>
14 #include <linux/irqflags.h>
15 #include <linux/sched.h>
16 #include <linux/stackdepot.h>
17 #include <linux/stacktrace.h>
18 #include <linux/nmi.h>
19 #include <linux/mm.h>
20 #include <linux/printk.h>
21
22 #define KMSAN_ALLOCA_MAGIC_ORIGIN 0xabcd0100
23 #define KMSAN_CHAIN_MAGIC_ORIGIN 0xabcd0200
24
25 #define KMSAN_POISON_NOCHECK 0x0
26 #define KMSAN_POISON_CHECK 0x1
27 #define KMSAN_POISON_FREE 0x2
28
29 #define KMSAN_ORIGIN_SIZE 4
30 #define KMSAN_MAX_ORIGIN_DEPTH 7
31
32 #define KMSAN_STACK_DEPTH 64
33
34 #define KMSAN_META_SHADOW (false)
35 #define KMSAN_META_ORIGIN (true)
36
37 extern bool kmsan_enabled;
38 extern int panic_on_kmsan;
39
40 /*
41 * KMSAN performs a lot of consistency checks that are currently enabled by
42 * default. BUG_ON is normally discouraged in the kernel, unless used for
43 * debugging, but KMSAN itself is a debugging tool, so it makes little sense to
44 * recover if something goes wrong.
45 */
46 #define KMSAN_WARN_ON(cond) \
47 ({ \
48 const bool __cond = WARN_ON(cond); \
49 if (unlikely(__cond)) { \
50 WRITE_ONCE(kmsan_enabled, false); \
51 if (panic_on_kmsan) { \
52 /* Can't call panic() here because */ \
53 /* of uaccess checks. */ \
54 BUG(); \
55 } \
56 } \
57 __cond; \
58 })
59
60 /*
61 * A pair of metadata pointers to be returned by the instrumentation functions.
62 */
63 struct shadow_origin_ptr {
64 void *shadow, *origin;
65 };
66
67 struct shadow_origin_ptr kmsan_get_shadow_origin_ptr(void *addr, u64 size,
68 bool store);
69 void *kmsan_get_metadata(void *addr, bool is_origin);
70 void __init kmsan_init_alloc_meta_for_range(void *start, void *end);
71
72 enum kmsan_bug_reason {
73 REASON_ANY,
74 REASON_COPY_TO_USER,
75 REASON_SUBMIT_URB,
76 };
77
78 void kmsan_print_origin(depot_stack_handle_t origin);
79
80 /**
81 * kmsan_report() - Report a use of uninitialized value.
82 * @origin: Stack ID of the uninitialized value.
83 * @address: Address at which the memory access happens.
84 * @size: Memory access size.
85 * @off_first: Offset (from @address) of the first byte to be reported.
86 * @off_last: Offset (from @address) of the last byte to be reported.
87 * @user_addr: When non-NULL, denotes the userspace address to which the kernel
88 * is leaking data.
89 * @reason: Error type from enum kmsan_bug_reason.
90 *
91 * kmsan_report() prints an error message for a consequent group of bytes
92 * sharing the same origin. If an uninitialized value is used in a comparison,
93 * this function is called once without specifying the addresses. When checking
94 * a memory range, KMSAN may call kmsan_report() multiple times with the same
95 * @address, @size, @user_addr and @reason, but different @off_first and
96 * @off_last corresponding to different @origin values.
97 */
98 void kmsan_report(depot_stack_handle_t origin, void *address, int size,
99 int off_first, int off_last, const void *user_addr,
100 enum kmsan_bug_reason reason);
101
102 DECLARE_PER_CPU(struct kmsan_ctx, kmsan_percpu_ctx);
103
kmsan_get_context(void)104 static __always_inline struct kmsan_ctx *kmsan_get_context(void)
105 {
106 return in_task() ? ¤t->kmsan_ctx : raw_cpu_ptr(&kmsan_percpu_ctx);
107 }
108
109 /*
110 * When a compiler hook or KMSAN runtime function is invoked, it may make a
111 * call to instrumented code and eventually call itself recursively. To avoid
112 * that, we guard the runtime entry regions with
113 * kmsan_enter_runtime()/kmsan_leave_runtime() and exit the hook if
114 * kmsan_in_runtime() is true.
115 *
116 * Non-runtime code may occasionally get executed in nested IRQs from the
117 * runtime code (e.g. when called via smp_call_function_single()). Because some
118 * KMSAN routines may take locks (e.g. for memory allocation), we conservatively
119 * bail out instead of calling them. To minimize the effect of this (potentially
120 * missing initialization events) kmsan_in_runtime() is not checked in
121 * non-blocking runtime functions.
122 */
kmsan_in_runtime(void)123 static __always_inline bool kmsan_in_runtime(void)
124 {
125 if ((hardirq_count() >> HARDIRQ_SHIFT) > 1)
126 return true;
127 if (in_nmi())
128 return true;
129 return kmsan_get_context()->kmsan_in_runtime;
130 }
131
kmsan_enter_runtime(void)132 static __always_inline void kmsan_enter_runtime(void)
133 {
134 struct kmsan_ctx *ctx;
135
136 ctx = kmsan_get_context();
137 KMSAN_WARN_ON(ctx->kmsan_in_runtime++);
138 }
139
kmsan_leave_runtime(void)140 static __always_inline void kmsan_leave_runtime(void)
141 {
142 struct kmsan_ctx *ctx = kmsan_get_context();
143
144 KMSAN_WARN_ON(--ctx->kmsan_in_runtime);
145 }
146
147 depot_stack_handle_t kmsan_save_stack(void);
148 depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags,
149 unsigned int extra_bits);
150
151 /*
152 * Pack and unpack the origin chain depth and UAF flag to/from the extra bits
153 * provided by the stack depot.
154 * The UAF flag is stored in the lowest bit, followed by the depth in the upper
155 * bits.
156 * set_dsh_extra_bits() is responsible for clamping the value.
157 */
kmsan_extra_bits(unsigned int depth,bool uaf)158 static __always_inline unsigned int kmsan_extra_bits(unsigned int depth,
159 bool uaf)
160 {
161 return (depth << 1) | uaf;
162 }
163
kmsan_uaf_from_eb(unsigned int extra_bits)164 static __always_inline bool kmsan_uaf_from_eb(unsigned int extra_bits)
165 {
166 return extra_bits & 1;
167 }
168
kmsan_depth_from_eb(unsigned int extra_bits)169 static __always_inline unsigned int kmsan_depth_from_eb(unsigned int extra_bits)
170 {
171 return extra_bits >> 1;
172 }
173
174 /*
175 * kmsan_internal_ functions are supposed to be very simple and not require the
176 * kmsan_in_runtime() checks.
177 */
178 void kmsan_internal_memmove_metadata(void *dst, void *src, size_t n);
179 void kmsan_internal_poison_memory(void *address, size_t size, gfp_t flags,
180 unsigned int poison_flags);
181 void kmsan_internal_unpoison_memory(void *address, size_t size, bool checked);
182 void kmsan_internal_set_shadow_origin(void *address, size_t size, int b,
183 u32 origin, bool checked);
184 depot_stack_handle_t kmsan_internal_chain_origin(depot_stack_handle_t id);
185
186 void kmsan_internal_task_create(struct task_struct *task);
187
188 bool kmsan_metadata_is_contiguous(void *addr, size_t size);
189 void kmsan_internal_check_memory(void *addr, size_t size, const void *user_addr,
190 int reason);
191
192 struct page *kmsan_vmalloc_to_page_or_null(void *vaddr);
193 void kmsan_setup_meta(struct page *page, struct page *shadow,
194 struct page *origin, int order);
195
196 /*
197 * kmsan_internal_is_module_addr() and kmsan_internal_is_vmalloc_addr() are
198 * non-instrumented versions of is_module_address() and is_vmalloc_addr() that
199 * are safe to call from KMSAN runtime without recursion.
200 */
kmsan_internal_is_module_addr(void * vaddr)201 static inline bool kmsan_internal_is_module_addr(void *vaddr)
202 {
203 return ((u64)vaddr >= MODULES_VADDR) && ((u64)vaddr < MODULES_END);
204 }
205
kmsan_internal_is_vmalloc_addr(void * addr)206 static inline bool kmsan_internal_is_vmalloc_addr(void *addr)
207 {
208 return ((u64)addr >= VMALLOC_START) && ((u64)addr < VMALLOC_END);
209 }
210
211 #endif /* __MM_KMSAN_KMSAN_H */
212