diff options
| author | Qian Cai <cai@lca.pw> | 2020-06-01 21:48:40 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-06-02 10:59:08 -0700 |
| commit | d6c1f098f2a7ba62627c9bc17cda28f534ef9e4a (patch) | |
| tree | 1af69e6f983385bb0618fb2d2e03e2a60656322d | |
| parent | 213516ac0752144ad1c82a0f8393f805c8abbc76 (diff) | |
mm/swap_state: fix a data race in swapin_nr_pages
"prev_offset" is a static variable in swapin_nr_pages() that can be
accessed concurrently with only mmap_sem held in read mode as noticed by
KCSAN,
BUG: KCSAN: data-race in swap_cluster_readahead / swap_cluster_readahead
write to 0xffffffff92763830 of 8 bytes by task 14795 on cpu 17:
swap_cluster_readahead+0x2a6/0x5e0
swapin_readahead+0x92/0x8dc
do_swap_page+0x49b/0xf20
__handle_mm_fault+0xcfb/0xd70
handle_mm_fault+0xfc/0x2f0
do_page_fault+0x263/0x715
page_fault+0x34/0x40
1 lock held by (dnf)/14795:
#0: ffff897bd2e98858 (&mm->mmap_sem#2){++++}-{3:3}, at: do_page_fault+0x143/0x715
do_user_addr_fault at arch/x86/mm/fault.c:1405
(inlined by) do_page_fault at arch/x86/mm/fault.c:1535
irq event stamp: 83493
count_memcg_event_mm+0x1a6/0x270
count_memcg_event_mm+0x119/0x270
__do_softirq+0x365/0x589
irq_exit+0xa2/0xc0
read to 0xffffffff92763830 of 8 bytes by task 1 on cpu 22:
swap_cluster_readahead+0xfd/0x5e0
swapin_readahead+0x92/0x8dc
do_swap_page+0x49b/0xf20
__handle_mm_fault+0xcfb/0xd70
handle_mm_fault+0xfc/0x2f0
do_page_fault+0x263/0x715
page_fault+0x34/0x40
1 lock held by systemd/1:
#0: ffff897c38f14858 (&mm->mmap_sem#2){++++}-{3:3}, at: do_page_fault+0x143/0x715
irq event stamp: 43530289
count_memcg_event_mm+0x1a6/0x270
count_memcg_event_mm+0x119/0x270
__do_softirq+0x365/0x589
irq_exit+0xa2/0xc0
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Marco Elver <elver@google.com>
Cc: Hugh Dickins <hughd@google.com>
Link: http://lkml.kernel.org/r/20200402213748.2237-1-cai@lca.pw
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/swap_state.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c index ebed37bbf7a3..8238954ae781 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -509,10 +509,11 @@ static unsigned long swapin_nr_pages(unsigned long offset) return 1; hits = atomic_xchg(&swapin_readahead_hits, 0); - pages = __swapin_nr_pages(prev_offset, offset, hits, max_pages, + pages = __swapin_nr_pages(READ_ONCE(prev_offset), offset, hits, + max_pages, atomic_read(&last_readahead_pages)); if (!hits) - prev_offset = offset; + WRITE_ONCE(prev_offset, offset); atomic_set(&last_readahead_pages, pages); return pages; |