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| author | Pei Li <peili.dev@gmail.com> | 2024-07-11 18:32:30 +0200 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-07-18 06:05:18 +0200 |
| commit | 7b7aca6d7c0f9b2d9400bfc57cb2b23cfbd5134d (patch) | |
| tree | 43e443ca63e0852120e37c9f5335edb7d31ea2ce /mm/page_io.c | |
| parent | hugetlbfs: ensure generic_hugetlb_get_unmapped_area() returns higher address ... (diff) | |
| download | linux-7b7aca6d7c0f9b2d9400bfc57cb2b23cfbd5134d.tar.xz linux-7b7aca6d7c0f9b2d9400bfc57cb2b23cfbd5134d.zip | |
mm: ignore data-race in __swap_writepage
Syzbot reported a possible data race:
BUG: KCSAN: data-race in __swap_writepage / scan_swap_map_slots
read-write to 0xffff888102fca610 of 8 bytes by task 7106 on cpu 1.
read to 0xffff888102fca610 of 8 bytes by task 7080 on cpu 0.
While we are in __swap_writepage to read sis->flags, scan_swap_map_slots
is trying to update it with SWP_SCANNING.
value changed: 0x0000000000008083 -> 0x0000000000004083.
While this can be updated non-atomicially, this won't affect
SWP_SYNCHRONOUS_IO, so we consider this data-race safe.
This is possibly introduced by commit 3222d8c2a7f8 ("block: remove
->rw_page"), where this if branch is introduced.
Link: https://lkml.kernel.org/r/20240711-bug13-v1-1-cea2b8ae8d76@gmail.com
Fixes: 3222d8c2a7f8 ("block: remove ->rw_page")
Signed-off-by: Pei Li <peili.dev@gmail.com>
Reported-by: syzbot+da25887cc13da6bf3b8c@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=da25887cc13da6bf3b8c
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/page_io.c')
| -rw-r--r-- | mm/page_io.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/mm/page_io.c b/mm/page_io.c index 6c1c1828bb88..ff8c99ee3af7 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -382,7 +382,12 @@ void __swap_writepage(struct folio *folio, struct writeback_control *wbc) */ if (data_race(sis->flags & SWP_FS_OPS)) swap_writepage_fs(folio, wbc); - else if (sis->flags & SWP_SYNCHRONOUS_IO) + /* + * ->flags can be updated non-atomicially (scan_swap_map_slots), + * but that will never affect SWP_SYNCHRONOUS_IO, so the data_race + * is safe. + */ + else if (data_race(sis->flags & SWP_SYNCHRONOUS_IO)) swap_writepage_bdev_sync(folio, wbc, sis); else swap_writepage_bdev_async(folio, wbc, sis); |