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/highmem.h>
6 #include <linux/page_ext.h>
7 #include <linux/poison.h>
8 #include <linux/ratelimit.h>
9 #include <linux/kasan.h>
10
11 static bool want_page_poisoning __read_mostly;
12
early_page_poison_param(char * buf)13 static int __init early_page_poison_param(char *buf)
14 {
15 if (!buf)
16 return -EINVAL;
17 return strtobool(buf, &want_page_poisoning);
18 }
19 early_param("page_poison", early_page_poison_param);
20
page_poisoning_enabled(void)21 bool page_poisoning_enabled(void)
22 {
23 /*
24 * Assumes that debug_pagealloc_enabled is set before
25 * free_all_bootmem.
26 * Page poisoning is debug page alloc for some arches. If
27 * either of those options are enabled, enable poisoning.
28 */
29 return (want_page_poisoning ||
30 (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
31 debug_pagealloc_enabled()));
32 }
33
poison_page(struct page * page)34 static void poison_page(struct page *page)
35 {
36 void *addr = kmap_atomic(page);
37
38 /* KASAN still think the page is in-use, so skip it. */
39 kasan_disable_current();
40 memset(addr, PAGE_POISON, PAGE_SIZE);
41 kasan_enable_current();
42 kunmap_atomic(addr);
43 }
44
poison_pages(struct page * page,int n)45 static void poison_pages(struct page *page, int n)
46 {
47 int i;
48
49 for (i = 0; i < n; i++)
50 poison_page(page + i);
51 }
52
single_bit_flip(unsigned char a,unsigned char b)53 static bool single_bit_flip(unsigned char a, unsigned char b)
54 {
55 unsigned char error = a ^ b;
56
57 return error && !(error & (error - 1));
58 }
59
check_poison_mem(unsigned char * mem,size_t bytes)60 static void check_poison_mem(unsigned char *mem, size_t bytes)
61 {
62 static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
63 unsigned char *start;
64 unsigned char *end;
65
66 if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
67 return;
68
69 start = memchr_inv(mem, PAGE_POISON, bytes);
70 if (!start)
71 return;
72
73 for (end = mem + bytes - 1; end > start; end--) {
74 if (*end != PAGE_POISON)
75 break;
76 }
77
78 if (!__ratelimit(&ratelimit))
79 return;
80 else if (start == end && single_bit_flip(*start, PAGE_POISON))
81 pr_err("pagealloc: single bit error\n");
82 else
83 pr_err("pagealloc: memory corruption\n");
84
85 print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
86 end - start + 1, 1);
87 dump_stack();
88 }
89
unpoison_page(struct page * page)90 static void unpoison_page(struct page *page)
91 {
92 void *addr;
93
94 addr = kmap_atomic(page);
95 /*
96 * Page poisoning when enabled poisons each and every page
97 * that is freed to buddy. Thus no extra check is done to
98 * see if a page was posioned.
99 */
100 check_poison_mem(addr, PAGE_SIZE);
101 kunmap_atomic(addr);
102 }
103
unpoison_pages(struct page * page,int n)104 static void unpoison_pages(struct page *page, int n)
105 {
106 int i;
107
108 for (i = 0; i < n; i++)
109 unpoison_page(page + i);
110 }
111
kernel_poison_pages(struct page * page,int numpages,int enable)112 void kernel_poison_pages(struct page *page, int numpages, int enable)
113 {
114 if (!page_poisoning_enabled())
115 return;
116
117 if (enable)
118 unpoison_pages(page, numpages);
119 else
120 poison_pages(page, numpages);
121 }
122
123 #ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
__kernel_map_pages(struct page * page,int numpages,int enable)124 void __kernel_map_pages(struct page *page, int numpages, int enable)
125 {
126 /* This function does nothing, all work is done via poison pages */
127 }
128 #endif
129