Description
In the Linux kernel, the following vulnerability has been resolved: loop: Avoid updating block size under exclusive owner Syzbot came up with a reproducer where a loop device block size is changed underneath a mounted filesystem. This causes a mismatch between the block device block size and the block size stored in the superblock causing confusion in various places such as fs/buffer.c. The particular issue triggered by syzbot was a warning in __getblk_slow() due to requested buffer size not matching block device block size. Fix the problem by getting exclusive hold of the loop device to change its block size. This fails if somebody (such as filesystem) has already an exclusive ownership of the block device and thus prevents modifying the loop device under some exclusive owner which doesn't expect it.
Affected products
linux: linux kernel
References6
- git.kernel.org/stable/c/139a000d20f2f38ce34296feddd641d730fe1c08 Patch
- git.kernel.org/stable/c/457d2c5e112fd08dc1039b1ae39a83ec1782360d Patch
- git.kernel.org/stable/c/5d67b30aefeb7a949040bbb1b4e3b84c5d29a624 Patch
- git.kernel.org/stable/c/7e49538288e523427beedd26993d446afef1a6fb Patch
- git.kernel.org/stable/c/b928438cc87c0bf7ae078e4b7b6e14261e84c5c5 Patch
- git.kernel.org/stable/c/46034518cae95db4abfde990c9ca1a0751855072
Metrics
- CVSS 3.1
-
5.5
MEDIUM
Score source: NVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - EPSS — exploit probability
- 0% percentile: 5 · as of 8 November 2026
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