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