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Vulnerability CVE-2024-35797
Published: 2024-05-17
| Description: |
In the Linux kernel, the following vulnerability has been resolved:
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. |
References: |
https://git.kernel.org/stable/c/b79f9e1ff27c994a4c452235ba09e672ec698e23
https://git.kernel.org/stable/c/d962f6c583458037dc7e529659b2b02b9dd3d94b
https://git.kernel.org/stable/c/24a0e73d544439bb9329fbbafac44299e548a677
https://git.kernel.org/stable/c/d5d39c707a4cf0bcc84680178677b97aa2cb2627
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