Loading...
1// SPDX-License-Identifier: GPL-2.0
2#include <linux/kernel.h>
3#include <linux/string.h>
4#include <linux/mm.h>
5#include <linux/mmdebug.h>
6#include <linux/highmem.h>
7#include <linux/poison.h>
8#include <linux/ratelimit.h>
9#include <linux/kasan.h>
10
11bool _page_poisoning_enabled_early;
12EXPORT_SYMBOL(_page_poisoning_enabled_early);
13DEFINE_STATIC_KEY_FALSE(_page_poisoning_enabled);
14EXPORT_SYMBOL(_page_poisoning_enabled);
15
16static int __init early_page_poison_param(char *buf)
17{
18 return kstrtobool(buf, &_page_poisoning_enabled_early);
19}
20early_param("page_poison", early_page_poison_param);
21
22static void poison_page(struct page *page)
23{
24 void *addr = kmap_local_page(page);
25
26 /* KASAN still think the page is in-use, so skip it. */
27 kasan_disable_current();
28 memset(kasan_reset_tag(addr), PAGE_POISON, PAGE_SIZE);
29 kasan_enable_current();
30 kunmap_local(addr);
31}
32
33void __kernel_poison_pages(struct page *page, int n)
34{
35 int i;
36
37 for (i = 0; i < n; i++)
38 poison_page(page + i);
39}
40
41static bool single_bit_flip(unsigned char a, unsigned char b)
42{
43 unsigned char error = a ^ b;
44
45 return error && !(error & (error - 1));
46}
47
48static void check_poison_mem(struct page *page, unsigned char *mem, size_t bytes)
49{
50 static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
51 unsigned char *start;
52 unsigned char *end;
53
54 start = memchr_inv(mem, PAGE_POISON, bytes);
55 if (!start)
56 return;
57
58 for (end = mem + bytes - 1; end > start; end--) {
59 if (*end != PAGE_POISON)
60 break;
61 }
62
63 if (!__ratelimit(&ratelimit))
64 return;
65 else if (start == end && single_bit_flip(*start, PAGE_POISON))
66 pr_err("pagealloc: single bit error\n");
67 else
68 pr_err("pagealloc: memory corruption\n");
69
70 print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
71 end - start + 1, 1);
72 dump_stack();
73 dump_page(page, "pagealloc: corrupted page details");
74}
75
76static void unpoison_page(struct page *page)
77{
78 void *addr;
79
80 addr = kmap_local_page(page);
81 kasan_disable_current();
82 /*
83 * Page poisoning when enabled poisons each and every page
84 * that is freed to buddy. Thus no extra check is done to
85 * see if a page was poisoned.
86 */
87 check_poison_mem(page, kasan_reset_tag(addr), PAGE_SIZE);
88 kasan_enable_current();
89 kunmap_local(addr);
90}
91
92void __kernel_unpoison_pages(struct page *page, int n)
93{
94 int i;
95
96 for (i = 0; i < n; i++)
97 unpoison_page(page + i);
98}
99
100#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
101void __kernel_map_pages(struct page *page, int numpages, int enable)
102{
103 /* This function does nothing, all work is done via poison pages */
104}
105#endif
1#include <linux/kernel.h>
2#include <linux/string.h>
3#include <linux/mm.h>
4#include <linux/highmem.h>
5#include <linux/page_ext.h>
6#include <linux/poison.h>
7#include <linux/ratelimit.h>
8
9static bool __page_poisoning_enabled __read_mostly;
10static bool want_page_poisoning __read_mostly;
11
12static int early_page_poison_param(char *buf)
13{
14 if (!buf)
15 return -EINVAL;
16
17 if (strcmp(buf, "on") == 0)
18 want_page_poisoning = true;
19 else if (strcmp(buf, "off") == 0)
20 want_page_poisoning = false;
21
22 return 0;
23}
24early_param("page_poison", early_page_poison_param);
25
26bool page_poisoning_enabled(void)
27{
28 return __page_poisoning_enabled;
29}
30
31static bool need_page_poisoning(void)
32{
33 return want_page_poisoning;
34}
35
36static void init_page_poisoning(void)
37{
38 /*
39 * page poisoning is debug page alloc for some arches. If either
40 * of those options are enabled, enable poisoning
41 */
42 if (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC)) {
43 if (!want_page_poisoning && !debug_pagealloc_enabled())
44 return;
45 } else {
46 if (!want_page_poisoning)
47 return;
48 }
49
50 __page_poisoning_enabled = true;
51}
52
53struct page_ext_operations page_poisoning_ops = {
54 .need = need_page_poisoning,
55 .init = init_page_poisoning,
56};
57
58static inline void set_page_poison(struct page *page)
59{
60 struct page_ext *page_ext;
61
62 page_ext = lookup_page_ext(page);
63 __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
64}
65
66static inline void clear_page_poison(struct page *page)
67{
68 struct page_ext *page_ext;
69
70 page_ext = lookup_page_ext(page);
71 __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
72}
73
74bool page_is_poisoned(struct page *page)
75{
76 struct page_ext *page_ext;
77
78 page_ext = lookup_page_ext(page);
79 if (!page_ext)
80 return false;
81
82 return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
83}
84
85static void poison_page(struct page *page)
86{
87 void *addr = kmap_atomic(page);
88
89 set_page_poison(page);
90 memset(addr, PAGE_POISON, PAGE_SIZE);
91 kunmap_atomic(addr);
92}
93
94static void poison_pages(struct page *page, int n)
95{
96 int i;
97
98 for (i = 0; i < n; i++)
99 poison_page(page + i);
100}
101
102static bool single_bit_flip(unsigned char a, unsigned char b)
103{
104 unsigned char error = a ^ b;
105
106 return error && !(error & (error - 1));
107}
108
109static void check_poison_mem(unsigned char *mem, size_t bytes)
110{
111 static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
112 unsigned char *start;
113 unsigned char *end;
114
115 if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
116 return;
117
118 start = memchr_inv(mem, PAGE_POISON, bytes);
119 if (!start)
120 return;
121
122 for (end = mem + bytes - 1; end > start; end--) {
123 if (*end != PAGE_POISON)
124 break;
125 }
126
127 if (!__ratelimit(&ratelimit))
128 return;
129 else if (start == end && single_bit_flip(*start, PAGE_POISON))
130 pr_err("pagealloc: single bit error\n");
131 else
132 pr_err("pagealloc: memory corruption\n");
133
134 print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
135 end - start + 1, 1);
136 dump_stack();
137}
138
139static void unpoison_page(struct page *page)
140{
141 void *addr;
142
143 if (!page_is_poisoned(page))
144 return;
145
146 addr = kmap_atomic(page);
147 check_poison_mem(addr, PAGE_SIZE);
148 clear_page_poison(page);
149 kunmap_atomic(addr);
150}
151
152static void unpoison_pages(struct page *page, int n)
153{
154 int i;
155
156 for (i = 0; i < n; i++)
157 unpoison_page(page + i);
158}
159
160void kernel_poison_pages(struct page *page, int numpages, int enable)
161{
162 if (!page_poisoning_enabled())
163 return;
164
165 if (enable)
166 unpoison_pages(page, numpages);
167 else
168 poison_pages(page, numpages);
169}
170
171#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
172void __kernel_map_pages(struct page *page, int numpages, int enable)
173{
174 /* This function does nothing, all work is done via poison pages */
175}
176#endif