The patch titled
Subject: mm: fix data race in PagePoisoned()
has been added to the -mm tree. Its filename is
mm-fix-data-race-in-pagepoisoned.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-fix-data-race-in-pagepoisoned.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-fix-data-race-in-pagepoisoned.patch
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------------------------------------------------------
From: Marco Elver <elver@xxxxxxxxxx>
Subject: mm: fix data race in PagePoisoned()
PagePoisoned() accesses page->flags which can be updated concurrently:
| BUG: KCSAN: data-race in next_uptodate_page / unlock_page
|
| write (marked) to 0xffffea00050f37c0 of 8 bytes by task 1872 on cpu 1:
| instrument_atomic_write include/linux/instrumented.h:87 [inline]
| clear_bit_unlock_is_negative_byte include/asm-generic/bitops/instrumented-lock.h:74 [inline]
| unlock_page+0x102/0x1b0 mm/filemap.c:1465
| filemap_map_pages+0x6c6/0x890 mm/filemap.c:3057
| ...
| read to 0xffffea00050f37c0 of 8 bytes by task 1873 on cpu 0:
| PagePoisoned include/linux/page-flags.h:204 [inline]
| PageReadahead include/linux/page-flags.h:382 [inline]
| next_uptodate_page+0x456/0x830 mm/filemap.c:2975
| ...
| CPU: 0 PID: 1873 Comm: systemd-udevd Not tainted 5.11.0-rc4-00001-gf9ce0be71d1f #1
To avoid the compiler tearing or otherwise optimizing the access, use
READ_ONCE() to access flags.
Link: https://lore.kernel.org/all/20210826144157.GA26950@xsang-OptiPlex-9020/
Link: https://lkml.kernel.org/r/20210913113542.2658064-1-elver@xxxxxxxxxx
Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/page-flags.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/include/linux/page-flags.h~mm-fix-data-race-in-pagepoisoned
+++ a/include/linux/page-flags.h
@@ -206,7 +206,7 @@ static __always_inline int PageCompound(
#define PAGE_POISON_PATTERN -1l
static inline int PagePoisoned(const struct page *page)
{
- return page->flags == PAGE_POISON_PATTERN;
+ return READ_ONCE(page->flags) == PAGE_POISON_PATTERN;
}
#ifdef CONFIG_DEBUG_VM
_
Patches currently in -mm which might be from elver@xxxxxxxxxx are
kasan-fix-kconfig-check-of-cc_has_working_nosanitize_address.patch
mm-fix-data-race-in-pagepoisoned.patch
