BackPup/Linux
1
0 Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-10-07 05:31:08 -04:00
Code Issues Packages Projects Releases Wiki Activity

mm/swap_state: fix a data race in swapin_nr_pages

Browse Source 
"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 <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Marco Elver <[email protected]>
Cc: Hugh Dickins <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Qian Cai authored and Linus Torvalds committed 2020-06-02 10:59:08 -07:00
1 parent 213516ac07
commit d6c1f098f2
1 file changed
+3 -2
Download Patch File Download Diff File Expand all files Collapse all files
mm/swap_state.c
+3 -2
View File
@@ -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;