CVE-2026-68442

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

btrfs: don't propagate EXTENT_FLAG_LOGGING to split extent maps

When btrfs_drop_extent_map_range() splits an extent map, the new split

maps inherit the original map's flags through a local 'flags' variable.

Commit f86f7a75e2fb ("btrfs: use the flags of an extent map to identify

the compression type") changed the EXTENT_FLAG_LOGGING clearing to

operate on em->flags instead of that local 'flags' copy, so a split of

an extent map that is currently being logged wrongly inherits

EXTENT_FLAG_LOGGING.

The flag is then never cleared on the split, and when it is freed while

still on the inode's modified_extents list (for example by the extent

map shrinker) it trips the WARN_ON(!list_empty(&em->list)) in

btrfs_free_extent_map() and leads to a use-after-free.

Clear EXTENT_FLAG_LOGGING from the local 'flags' copy used for the

splits and only clear EXTENT_FLAG_PINNED from em->flags, restoring the

behaviour prior to f86f7a75e2fb

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References