linux/mm/page_poison.c
Sergei Trofimovich f58bd538e6 mm: page_poison: print page info when corruption is caught
When page_poison detects page corruption it's useful to see who freed a
page recently to have a guess where write-after-free corruption happens.

After this change corruption report has extra page data.
Example report from real corruption (includes only page_pwner part):

    pagealloc: memory corruption
    e00000014cd61d10: 11 00 00 00 00 00 00 00 30 1d d2 ff ff 0f 00 60  ........0......`
    e00000014cd61d20: b0 1d d2 ff ff 0f 00 60 90 fe 1c 00 08 00 00 20  .......`.......
    ...
    CPU: 1 PID: 220402 Comm: cc1plus Not tainted 5.12.0-rc5-00107-g9720c6f59ecf 
    Hardware name: hp server rx3600, BIOS 04.03 04/08/2008
    ...
    Call Trace:
     [<a000000100015210>] show_stack+0x90/0xc0
     [<a000000101163390>] dump_stack+0x150/0x1c0
     [<a0000001003f1e90>] __kernel_unpoison_pages+0x410/0x440
     [<a0000001003c2460>] get_page_from_freelist+0x1460/0x2ca0
     [<a0000001003c6be0>] __alloc_pages_nodemask+0x3c0/0x660
     [<a0000001003ed690>] alloc_pages_vma+0xb0/0x500
     [<a00000010037deb0>] __handle_mm_fault+0x1230/0x1fe0
     [<a00000010037ef70>] handle_mm_fault+0x310/0x4e0
     [<a00000010005dc70>] ia64_do_page_fault+0x1f0/0xb80
     [<a00000010000ca00>] ia64_leave_kernel+0x0/0x270
    page_owner tracks the page as freed
    page allocated via order 0, migratetype Movable,
      gfp_mask 0x100dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), pid 37, ts 8173444098740
     __reset_page_owner+0x40/0x200
     free_pcp_prepare+0x4d0/0x600
     free_unref_page+0x20/0x1c0
     __put_page+0x110/0x1a0
     migrate_pages+0x16d0/0x1dc0
     compact_zone+0xfc0/0x1aa0
     proactive_compact_node+0xd0/0x1e0
     kcompactd+0x550/0x600
     kthread+0x2c0/0x2e0
     call_payload+0x50/0x80

Here we can see that page was freed by page migration but something
managed to write to it afterwards.

[slyfox@gentoo.org: s/dump_page_owner/dump_page/, per Vlastimil]
  Link: https://lkml.kernel.org/r/20210407230800.1086854-1-slyfox@gentoo.org

Link: https://lkml.kernel.org/r/20210404141735.2152984-1-slyfox@gentoo.org
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-04-30 11:20:36 -07:00

107 lines
2.5 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/mmdebug.h>
#include <linux/highmem.h>
#include <linux/page_ext.h>
#include <linux/poison.h>
#include <linux/ratelimit.h>
#include <linux/kasan.h>
bool _page_poisoning_enabled_early;
EXPORT_SYMBOL(_page_poisoning_enabled_early);
DEFINE_STATIC_KEY_FALSE(_page_poisoning_enabled);
EXPORT_SYMBOL(_page_poisoning_enabled);
static int __init early_page_poison_param(char *buf)
{
return kstrtobool(buf, &_page_poisoning_enabled_early);
}
early_param("page_poison", early_page_poison_param);
static void poison_page(struct page *page)
{
void *addr = kmap_atomic(page);
/* KASAN still think the page is in-use, so skip it. */
kasan_disable_current();
memset(kasan_reset_tag(addr), PAGE_POISON, PAGE_SIZE);
kasan_enable_current();
kunmap_atomic(addr);
}
void __kernel_poison_pages(struct page *page, int n)
{
int i;
for (i = 0; i < n; i++)
poison_page(page + i);
}
static bool single_bit_flip(unsigned char a, unsigned char b)
{
unsigned char error = a ^ b;
return error && !(error & (error - 1));
}
static void check_poison_mem(struct page *page, unsigned char *mem, size_t bytes)
{
static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
unsigned char *start;
unsigned char *end;
start = memchr_inv(mem, PAGE_POISON, bytes);
if (!start)
return;
for (end = mem + bytes - 1; end > start; end--) {
if (*end != PAGE_POISON)
break;
}
if (!__ratelimit(&ratelimit))
return;
else if (start == end && single_bit_flip(*start, PAGE_POISON))
pr_err("pagealloc: single bit error\n");
else
pr_err("pagealloc: memory corruption\n");
print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
end - start + 1, 1);
dump_stack();
dump_page(page, "pagealloc: corrupted page details");
}
static void unpoison_page(struct page *page)
{
void *addr;
addr = kmap_atomic(page);
kasan_disable_current();
/*
* Page poisoning when enabled poisons each and every page
* that is freed to buddy. Thus no extra check is done to
* see if a page was poisoned.
*/
check_poison_mem(page, kasan_reset_tag(addr), PAGE_SIZE);
kasan_enable_current();
kunmap_atomic(addr);
}
void __kernel_unpoison_pages(struct page *page, int n)
{
int i;
for (i = 0; i < n; i++)
unpoison_page(page + i);
}
#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
void __kernel_map_pages(struct page *page, int numpages, int enable)
{
/* This function does nothing, all work is done via poison pages */
}
#endif