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author | Johannes Weiner <hannes@cmpxchg.org> | 2024-03-15 12:55:56 +0300 |
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committer | Andrew Morton <akpm@linux-foundation.org> | 2024-03-26 21:07:20 +0300 |
commit | d5d39c707a4cf0bcc84680178677b97aa2cb2627 (patch) | |
tree | d0eb07a289d1765abe38aa2bb1265d519842651f /.get_maintainer.ignore | |
parent | 9cecde80aae0fb0aa44425575d5aca71bc646d89 (diff) | |
download | linux-d5d39c707a4cf0bcc84680178677b97aa2cb2627.tar.xz |
mm: cachestat: fix two shmem bugs
When cachestat on shmem races with swapping and invalidation, there
are two possible bugs:
1) A swapin error can have resulted in a poisoned swap entry in the
shmem inode's xarray. Calling get_shadow_from_swap_cache() on it
will result in an out-of-bounds access to swapper_spaces[].
Validate the entry with non_swap_entry() before going further.
2) When we find a valid swap entry in the shmem's inode, the shadow
entry in the swapcache might not exist yet: swap IO is still in
progress and we're before __remove_mapping; swapin, invalidation,
or swapoff have removed the shadow from swapcache after we saw the
shmem swap entry.
This will send a NULL to workingset_test_recent(). The latter
purely operates on pointer bits, so it won't crash - node 0, memcg
ID 0, eviction timestamp 0, etc. are all valid inputs - but it's a
bogus test. In theory that could result in a false "recently
evicted" count.
Such a false positive wouldn't be the end of the world. But for
code clarity and (future) robustness, be explicit about this case.
Bail on get_shadow_from_swap_cache() returning NULL.
Link: https://lkml.kernel.org/r/20240315095556.GC581298@cmpxchg.org
Fixes: cf264e1329fb ("cachestat: implement cachestat syscall")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Chengming Zhou <chengming.zhou@linux.dev> [Bug #1]
Reported-by: Jann Horn <jannh@google.com> [Bug #2]
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: <stable@vger.kernel.org> [v6.5+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to '.get_maintainer.ignore')
0 files changed, 0 insertions, 0 deletions