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
11 bool _page_poisoning_enabled_early;
12 EXPORT_SYMBOL(_page_poisoning_enabled_early);
13 DEFINE_STATIC_KEY_FALSE(_page_poisoning_enabled);
14 EXPORT_SYMBOL(_page_poisoning_enabled);
15
early_page_poison_param(char * buf)16 static int __init early_page_poison_param(char *buf)
17 {
18 return kstrtobool(buf, &_page_poisoning_enabled_early);
19 }
20 early_param("page_poison", early_page_poison_param);
21
poison_page(struct page * page)22 static void poison_page(struct page *page)
23 {
24 void *addr = kmap_atomic(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_atomic(addr);
31 }
32
__kernel_poison_pages(struct page * page,int n)33 void __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
single_bit_flip(unsigned char a,unsigned char b)41 static 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
check_poison_mem(struct page * page,unsigned char * mem,size_t bytes)48 static 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
unpoison_page(struct page * page)76 static void unpoison_page(struct page *page)
77 {
78 void *addr;
79
80 addr = kmap_atomic(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_atomic(addr);
90 }
91
__kernel_unpoison_pages(struct page * page,int n)92 void __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
__kernel_map_pages(struct page * page,int numpages,int enable)101 void __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
106