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
11static bool want_page_poisoning __read_mostly;
12
13static int __init early_page_poison_param(char *buf)
14{
15 if (!buf)
16 return -EINVAL;
17 return strtobool(buf, &want_page_poisoning);
18}
19early_param("page_poison", early_page_poison_param);
20
21/**
22 * page_poisoning_enabled - check if page poisoning is enabled
23 *
24 * Return true if page poisoning is enabled, or false if not.
25 */
26bool page_poisoning_enabled(void)
27{
28 /*
29 * Assumes that debug_pagealloc_enabled is set before
30 * memblock_free_all.
31 * Page poisoning is debug page alloc for some arches. If
32 * either of those options are enabled, enable poisoning.
33 */
34 return (want_page_poisoning ||
35 (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
36 debug_pagealloc_enabled()));
37}
38EXPORT_SYMBOL_GPL(page_poisoning_enabled);
39
40static void poison_page(struct page *page)
41{
42 void *addr = kmap_atomic(page);
43
44 /* KASAN still think the page is in-use, so skip it. */
45 kasan_disable_current();
46 memset(addr, PAGE_POISON, PAGE_SIZE);
47 kasan_enable_current();
48 kunmap_atomic(addr);
49}
50
51static void poison_pages(struct page *page, int n)
52{
53 int i;
54
55 for (i = 0; i < n; i++)
56 poison_page(page + i);
57}
58
59static bool single_bit_flip(unsigned char a, unsigned char b)
60{
61 unsigned char error = a ^ b;
62
63 return error && !(error & (error - 1));
64}
65
66static void check_poison_mem(unsigned char *mem, size_t bytes)
67{
68 static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
69 unsigned char *start;
70 unsigned char *end;
71
72 if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
73 return;
74
75 start = memchr_inv(mem, PAGE_POISON, bytes);
76 if (!start)
77 return;
78
79 for (end = mem + bytes - 1; end > start; end--) {
80 if (*end != PAGE_POISON)
81 break;
82 }
83
84 if (!__ratelimit(&ratelimit))
85 return;
86 else if (start == end && single_bit_flip(*start, PAGE_POISON))
87 pr_err("pagealloc: single bit error\n");
88 else
89 pr_err("pagealloc: memory corruption\n");
90
91 print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
92 end - start + 1, 1);
93 dump_stack();
94}
95
96static void unpoison_page(struct page *page)
97{
98 void *addr;
99
100 addr = kmap_atomic(page);
101 /*
102 * Page poisoning when enabled poisons each and every page
103 * that is freed to buddy. Thus no extra check is done to
104 * see if a page was posioned.
105 */
106 check_poison_mem(addr, PAGE_SIZE);
107 kunmap_atomic(addr);
108}
109
110static void unpoison_pages(struct page *page, int n)
111{
112 int i;
113
114 for (i = 0; i < n; i++)
115 unpoison_page(page + i);
116}
117
118void kernel_poison_pages(struct page *page, int numpages, int enable)
119{
120 if (!page_poisoning_enabled())
121 return;
122
123 if (enable)
124 unpoison_pages(page, numpages);
125 else
126 poison_pages(page, numpages);
127}
128
129#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
130void __kernel_map_pages(struct page *page, int numpages, int enable)
131{
132 /* This function does nothing, all work is done via poison pages */
133}
134#endif
135