CVE-2022-50668

Description

In the Linux kernel, the following vulnerability has been resolved: ext4: fix deadlock due to mbcache entry corruption When manipulating xattr blocks, we can deadlock infinitely looping inside ext4_xattr_block_set() where we constantly keep finding xattr block for reuse in mbcache but we are unable to reuse it because its reference count is too big. This happens because cache entry for the xattr block is marked as reusable (e_reusable set) although its reference count is too big. When this inconsistency happens, this inconsistent state is kept indefinitely and so ext4_xattr_block_set() keeps retrying indefinitely. The inconsistent state is caused by non-atomic update of e_reusable bit. e_reusable is part of a bitfield and e_reusable update can race with update of e_referenced bit in the same bitfield resulting in loss of one of the updates. Fix the problem by using atomic bitops instead. This bug has been around for many years, but it became *much* easier to hit after commit 65f8b80053a1 ("ext4: fix race when reusing xattr blocks").

PUBLISHED Reserved 2025-12-09 | Published 2025-12-09 | Updated 2025-12-09 | Assigner Linux

Product status

References

git.kernel.org/...c/efaa0ca678f56d47316a08030b2515678cebbc50

git.kernel.org/...c/af53065276376750dfac35a7248af18806404c5d

git.kernel.org/...c/1be16a0c2f10186df505e28b0cc92d7f3366e2a8

git.kernel.org/...c/5bc0b2fda4b47c86278f7c6d30c211f425bf51cf

git.kernel.org/...c/127b80cefb941a81255c72f11081123f3a705369

git.kernel.org/...c/cc1538c693d25e282bed8c54b65c914a04023a78

git.kernel.org/...c/a44e84a9b7764c72896f7241a0ec9ac7e7ef38dd

cve.org (CVE-2022-50668)

nvd.nist.gov (CVE-2022-50668)

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