From: Sergei Trofimovich <slyfox@xxxxxxxxxx>
Subject: 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 #245
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@xxxxxxxxxx: s/dump_page_owner/dump_page/, per Vlastimil]
Link: https://lkml.kernel.org/r/20210407230800.1086854-1-slyfox@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20210404141735.2152984-1-slyfox@xxxxxxxxxx
Signed-off-by: Sergei Trofimovich <slyfox@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_poison.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/mm/page_poison.c~mm-page_poison-print-page-owner-info-when-corruption-is-caught
+++ a/mm/page_poison.c
@@ -2,6 +2,7 @@
#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>
@@ -45,7 +46,7 @@ static bool single_bit_flip(unsigned cha
return error && !(error & (error - 1));
}
-static void check_poison_mem(unsigned char *mem, size_t bytes)
+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;
@@ -70,6 +71,7 @@ static void check_poison_mem(unsigned ch
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)
@@ -83,7 +85,7 @@ static void unpoison_page(struct page *p
* that is freed to buddy. Thus no extra check is done to
* see if a page was poisoned.
*/
- check_poison_mem(kasan_reset_tag(addr), PAGE_SIZE);
+ check_poison_mem(page, kasan_reset_tag(addr), PAGE_SIZE);
kasan_enable_current();
kunmap_atomic(addr);
}
_
