CVE-2024-42104

/// Technical description

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

nilfs2: add missing check for inode numbers on directory entries

Syzbot reported that mounting and unmounting a specific pattern of

corrupted nilfs2 filesystem images causes a use-after-free of metadata

file inodes, which triggers a kernel bug in lru_add_fn().

As Jan Kara pointed out, this is because the link count of a metadata file

gets corrupted to 0, and nilfs_evict_inode(), which is called from iput(),

tries to delete that inode (ifile inode in this case).

The inconsistency occurs because directories containing the inode numbers

of these metadata files that should not be visible in the namespace are

read without checking.

Fix this issue by treating the inode numbers of these internal files as

errors in the sanity check helper when reading directory folios/pages.

Also thanks to Hillf Danton and Matthew Wilcox for their initial mm-layer

analysis.

/// 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