CVE-2025-38709

NameCVE-2025-38709
DescriptionIn 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.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
linux (PTS)bullseye5.10.223-1vulnerable
bullseye (security)5.10.244-1vulnerable
bookworm6.1.148-1vulnerable
bookworm (security)6.1.153-1vulnerable
trixie6.12.43-1fixed
trixie (security)6.12.48-1fixed
forky6.16.12-2fixed
sid6.17.6-1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
linuxsourcetrixie6.12.43-1
linuxsource(unstable)6.16.3-1

Notes

https://git.kernel.org/linus/7e49538288e523427beedd26993d446afef1a6fb (6.17-rc1)

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