1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * This file contains core generic KASAN code.
4 *
5 * Copyright (c) 2014 Samsung Electronics Co., Ltd.
6 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
7 *
8 * Some code borrowed from https://github.com/xairy/kasan-prototype by
9 * Andrey Konovalov <andreyknvl@gmail.com>
10 */
11
12 #include <linux/export.h>
13 #include <linux/interrupt.h>
14 #include <linux/init.h>
15 #include <linux/kasan.h>
16 #include <linux/kernel.h>
17 #include <linux/kfence.h>
18 #include <linux/kmemleak.h>
19 #include <linux/linkage.h>
20 #include <linux/memblock.h>
21 #include <linux/memory.h>
22 #include <linux/mm.h>
23 #include <linux/module.h>
24 #include <linux/printk.h>
25 #include <linux/sched.h>
26 #include <linux/sched/task_stack.h>
27 #include <linux/slab.h>
28 #include <linux/stacktrace.h>
29 #include <linux/string.h>
30 #include <linux/types.h>
31 #include <linux/vmalloc.h>
32 #include <linux/bug.h>
33
34 #include "kasan.h"
35 #include "../slab.h"
36
37 /*
38 * All functions below always inlined so compiler could
39 * perform better optimizations in each of __asan_loadX/__assn_storeX
40 * depending on memory access size X.
41 */
42
memory_is_poisoned_1(unsigned long addr)43 static __always_inline bool memory_is_poisoned_1(unsigned long addr)
44 {
45 s8 shadow_value = *(s8 *)kasan_mem_to_shadow((void *)addr);
46
47 if (unlikely(shadow_value)) {
48 s8 last_accessible_byte = addr & KASAN_GRANULE_MASK;
49 return unlikely(last_accessible_byte >= shadow_value);
50 }
51
52 return false;
53 }
54
memory_is_poisoned_2_4_8(unsigned long addr,unsigned long size)55 static __always_inline bool memory_is_poisoned_2_4_8(unsigned long addr,
56 unsigned long size)
57 {
58 u8 *shadow_addr = (u8 *)kasan_mem_to_shadow((void *)addr);
59
60 /*
61 * Access crosses 8(shadow size)-byte boundary. Such access maps
62 * into 2 shadow bytes, so we need to check them both.
63 */
64 if (unlikely(((addr + size - 1) & KASAN_GRANULE_MASK) < size - 1))
65 return *shadow_addr || memory_is_poisoned_1(addr + size - 1);
66
67 return memory_is_poisoned_1(addr + size - 1);
68 }
69
memory_is_poisoned_16(unsigned long addr)70 static __always_inline bool memory_is_poisoned_16(unsigned long addr)
71 {
72 u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
73
74 /* Unaligned 16-bytes access maps into 3 shadow bytes. */
75 if (unlikely(!IS_ALIGNED(addr, KASAN_GRANULE_SIZE)))
76 return *shadow_addr || memory_is_poisoned_1(addr + 15);
77
78 return *shadow_addr;
79 }
80
bytes_is_nonzero(const u8 * start,size_t size)81 static __always_inline unsigned long bytes_is_nonzero(const u8 *start,
82 size_t size)
83 {
84 while (size) {
85 if (unlikely(*start))
86 return (unsigned long)start;
87 start++;
88 size--;
89 }
90
91 return 0;
92 }
93
memory_is_nonzero(const void * start,const void * end)94 static __always_inline unsigned long memory_is_nonzero(const void *start,
95 const void *end)
96 {
97 unsigned int words;
98 unsigned long ret;
99 unsigned int prefix = (unsigned long)start % 8;
100
101 if (end - start <= 16)
102 return bytes_is_nonzero(start, end - start);
103
104 if (prefix) {
105 prefix = 8 - prefix;
106 ret = bytes_is_nonzero(start, prefix);
107 if (unlikely(ret))
108 return ret;
109 start += prefix;
110 }
111
112 words = (end - start) / 8;
113 while (words) {
114 if (unlikely(*(u64 *)start))
115 return bytes_is_nonzero(start, 8);
116 start += 8;
117 words--;
118 }
119
120 return bytes_is_nonzero(start, (end - start) % 8);
121 }
122
memory_is_poisoned_n(unsigned long addr,size_t size)123 static __always_inline bool memory_is_poisoned_n(unsigned long addr,
124 size_t size)
125 {
126 unsigned long ret;
127
128 ret = memory_is_nonzero(kasan_mem_to_shadow((void *)addr),
129 kasan_mem_to_shadow((void *)addr + size - 1) + 1);
130
131 if (unlikely(ret)) {
132 unsigned long last_byte = addr + size - 1;
133 s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);
134
135 if (unlikely(ret != (unsigned long)last_shadow ||
136 ((long)(last_byte & KASAN_GRANULE_MASK) >= *last_shadow)))
137 return true;
138 }
139 return false;
140 }
141
memory_is_poisoned(unsigned long addr,size_t size)142 static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
143 {
144 if (__builtin_constant_p(size)) {
145 switch (size) {
146 case 1:
147 return memory_is_poisoned_1(addr);
148 case 2:
149 case 4:
150 case 8:
151 return memory_is_poisoned_2_4_8(addr, size);
152 case 16:
153 return memory_is_poisoned_16(addr);
154 default:
155 BUILD_BUG();
156 }
157 }
158
159 return memory_is_poisoned_n(addr, size);
160 }
161
check_region_inline(unsigned long addr,size_t size,bool write,unsigned long ret_ip)162 static __always_inline bool check_region_inline(unsigned long addr,
163 size_t size, bool write,
164 unsigned long ret_ip)
165 {
166 if (unlikely(size == 0))
167 return true;
168
169 if (unlikely(addr + size < addr))
170 return !kasan_report(addr, size, write, ret_ip);
171
172 if (unlikely((void *)addr <
173 kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
174 return !kasan_report(addr, size, write, ret_ip);
175 }
176
177 if (likely(!memory_is_poisoned(addr, size)))
178 return true;
179
180 return !kasan_report(addr, size, write, ret_ip);
181 }
182
kasan_check_range(unsigned long addr,size_t size,bool write,unsigned long ret_ip)183 bool kasan_check_range(unsigned long addr, size_t size, bool write,
184 unsigned long ret_ip)
185 {
186 return check_region_inline(addr, size, write, ret_ip);
187 }
188
kasan_byte_accessible(const void * addr)189 bool kasan_byte_accessible(const void *addr)
190 {
191 s8 shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr));
192
193 return shadow_byte >= 0 && shadow_byte < KASAN_GRANULE_SIZE;
194 }
195
kasan_cache_shrink(struct kmem_cache * cache)196 void kasan_cache_shrink(struct kmem_cache *cache)
197 {
198 kasan_quarantine_remove_cache(cache);
199 }
200
kasan_cache_shutdown(struct kmem_cache * cache)201 void kasan_cache_shutdown(struct kmem_cache *cache)
202 {
203 if (!__kmem_cache_empty(cache))
204 kasan_quarantine_remove_cache(cache);
205 }
206
register_global(struct kasan_global * global)207 static void register_global(struct kasan_global *global)
208 {
209 size_t aligned_size = round_up(global->size, KASAN_GRANULE_SIZE);
210
211 kasan_unpoison(global->beg, global->size, false);
212
213 kasan_poison(global->beg + aligned_size,
214 global->size_with_redzone - aligned_size,
215 KASAN_GLOBAL_REDZONE, false);
216 }
217
__asan_register_globals(struct kasan_global * globals,size_t size)218 void __asan_register_globals(struct kasan_global *globals, size_t size)
219 {
220 int i;
221
222 for (i = 0; i < size; i++)
223 register_global(&globals[i]);
224 }
225 EXPORT_SYMBOL(__asan_register_globals);
226
__asan_unregister_globals(struct kasan_global * globals,size_t size)227 void __asan_unregister_globals(struct kasan_global *globals, size_t size)
228 {
229 }
230 EXPORT_SYMBOL(__asan_unregister_globals);
231
232 #define DEFINE_ASAN_LOAD_STORE(size) \
233 void __asan_load##size(unsigned long addr) \
234 { \
235 check_region_inline(addr, size, false, _RET_IP_); \
236 } \
237 EXPORT_SYMBOL(__asan_load##size); \
238 __alias(__asan_load##size) \
239 void __asan_load##size##_noabort(unsigned long); \
240 EXPORT_SYMBOL(__asan_load##size##_noabort); \
241 void __asan_store##size(unsigned long addr) \
242 { \
243 check_region_inline(addr, size, true, _RET_IP_); \
244 } \
245 EXPORT_SYMBOL(__asan_store##size); \
246 __alias(__asan_store##size) \
247 void __asan_store##size##_noabort(unsigned long); \
248 EXPORT_SYMBOL(__asan_store##size##_noabort)
249
250 DEFINE_ASAN_LOAD_STORE(1);
251 DEFINE_ASAN_LOAD_STORE(2);
252 DEFINE_ASAN_LOAD_STORE(4);
253 DEFINE_ASAN_LOAD_STORE(8);
254 DEFINE_ASAN_LOAD_STORE(16);
255
__asan_loadN(unsigned long addr,size_t size)256 void __asan_loadN(unsigned long addr, size_t size)
257 {
258 kasan_check_range(addr, size, false, _RET_IP_);
259 }
260 EXPORT_SYMBOL(__asan_loadN);
261
262 __alias(__asan_loadN)
263 void __asan_loadN_noabort(unsigned long, size_t);
264 EXPORT_SYMBOL(__asan_loadN_noabort);
265
__asan_storeN(unsigned long addr,size_t size)266 void __asan_storeN(unsigned long addr, size_t size)
267 {
268 kasan_check_range(addr, size, true, _RET_IP_);
269 }
270 EXPORT_SYMBOL(__asan_storeN);
271
272 __alias(__asan_storeN)
273 void __asan_storeN_noabort(unsigned long, size_t);
274 EXPORT_SYMBOL(__asan_storeN_noabort);
275
276 /* to shut up compiler complaints */
__asan_handle_no_return(void)277 void __asan_handle_no_return(void) {}
278 EXPORT_SYMBOL(__asan_handle_no_return);
279
280 /* Emitted by compiler to poison alloca()ed objects. */
__asan_alloca_poison(unsigned long addr,size_t size)281 void __asan_alloca_poison(unsigned long addr, size_t size)
282 {
283 size_t rounded_up_size = round_up(size, KASAN_GRANULE_SIZE);
284 size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) -
285 rounded_up_size;
286 size_t rounded_down_size = round_down(size, KASAN_GRANULE_SIZE);
287
288 const void *left_redzone = (const void *)(addr -
289 KASAN_ALLOCA_REDZONE_SIZE);
290 const void *right_redzone = (const void *)(addr + rounded_up_size);
291
292 WARN_ON(!IS_ALIGNED(addr, KASAN_ALLOCA_REDZONE_SIZE));
293
294 kasan_unpoison((const void *)(addr + rounded_down_size),
295 size - rounded_down_size, false);
296 kasan_poison(left_redzone, KASAN_ALLOCA_REDZONE_SIZE,
297 KASAN_ALLOCA_LEFT, false);
298 kasan_poison(right_redzone, padding_size + KASAN_ALLOCA_REDZONE_SIZE,
299 KASAN_ALLOCA_RIGHT, false);
300 }
301 EXPORT_SYMBOL(__asan_alloca_poison);
302
303 /* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */
__asan_allocas_unpoison(const void * stack_top,const void * stack_bottom)304 void __asan_allocas_unpoison(const void *stack_top, const void *stack_bottom)
305 {
306 if (unlikely(!stack_top || stack_top > stack_bottom))
307 return;
308
309 kasan_unpoison(stack_top, stack_bottom - stack_top, false);
310 }
311 EXPORT_SYMBOL(__asan_allocas_unpoison);
312
313 /* Emitted by the compiler to [un]poison local variables. */
314 #define DEFINE_ASAN_SET_SHADOW(byte) \
315 void __asan_set_shadow_##byte(const void *addr, size_t size) \
316 { \
317 __memset((void *)addr, 0x##byte, size); \
318 } \
319 EXPORT_SYMBOL(__asan_set_shadow_##byte)
320
321 DEFINE_ASAN_SET_SHADOW(00);
322 DEFINE_ASAN_SET_SHADOW(f1);
323 DEFINE_ASAN_SET_SHADOW(f2);
324 DEFINE_ASAN_SET_SHADOW(f3);
325 DEFINE_ASAN_SET_SHADOW(f5);
326 DEFINE_ASAN_SET_SHADOW(f8);
327
kasan_record_aux_stack(void * addr)328 void kasan_record_aux_stack(void *addr)
329 {
330 struct page *page = kasan_addr_to_page(addr);
331 struct kmem_cache *cache;
332 struct kasan_alloc_meta *alloc_meta;
333 void *object;
334
335 if (is_kfence_address(addr) || !(page && PageSlab(page)))
336 return;
337
338 cache = page->slab_cache;
339 object = nearest_obj(cache, page, addr);
340 alloc_meta = kasan_get_alloc_meta(cache, object);
341 if (!alloc_meta)
342 return;
343
344 alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];
345 alloc_meta->aux_stack[0] = kasan_save_stack(GFP_NOWAIT);
346 }
347
kasan_set_free_info(struct kmem_cache * cache,void * object,u8 tag)348 void kasan_set_free_info(struct kmem_cache *cache,
349 void *object, u8 tag)
350 {
351 struct kasan_free_meta *free_meta;
352
353 free_meta = kasan_get_free_meta(cache, object);
354 if (!free_meta)
355 return;
356
357 kasan_set_track(&free_meta->free_track, GFP_NOWAIT);
358 /* The object was freed and has free track set. */
359 *(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREETRACK;
360 }
361
kasan_get_free_track(struct kmem_cache * cache,void * object,u8 tag)362 struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
363 void *object, u8 tag)
364 {
365 if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_KMALLOC_FREETRACK)
366 return NULL;
367 /* Free meta must be present with KASAN_KMALLOC_FREETRACK. */
368 return &kasan_get_free_meta(cache, object)->free_track;
369 }
370