CVE-2024-57924
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk10th percentile - higher than 10% of all known CVEs
Summary
In the Linux kernel, a vulnerability was found due to overly strict assertions (WARN_ON) when file handle encoding fails. These assertions are incorrect because encoding can fail for various reasons, and main users (nfsd, name_to_handle_at) are already prepared to handle errors.
Risk Assessment
Unnecessary assertions may cause unexpected warnings and potentially destabilize the system, especially in configurations with overlayfs, inotify, and drop_caches. This can lead to unpredictable kernel behavior and complicate diagnostics.
Recommendation
Apply the patch that removes the incorrect WARN_ON assertions in exportfs_encode_fh() and exportfs_encode_fid(). Update the kernel to a version containing the fix (e.g., v6.13 or later) or manually patch older stable kernels.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: fs: relax assertions on failure to encode file handles Encoding file handles is usually performed by a filesystem >encode_fh() method that may fail for various reasons. The legacy users of exportfs_encode_fh(), namely, nfsd and name_to_handle_at(2) syscall are ready to cope with the possibility of failure to encode a file handle. There are a few other users of exportfs_encode_{fh,fid}() that currently have a WARN_ON() assertion when ->encode_fh() fails. Relax those assertions because they are wrong. The second linked bug report states commit 16aac5ad1fa9 ("ovl: support encoding non-decodable file handles") in v6.6 as the regressing commit, but this is not accurate. The aforementioned commit only increases the chances of the assertion and allows triggering the assertion with the reproducer using overlayfs, inotify and drop_caches. Triggering this assertion was always possible with other filesystems and other reasons of ->encode_fh() failures and more particularly, it was also possible with the exact same reproducer using overlayfs that is mounted with options index=on,nfs_export=on also on kernels < v6.6. Therefore, I am not listing the aforementioned commit as a Fixes commit. Backport hint: this patch will have a trivial conflict applying to v6.6.y, and other trivial conflicts applying to stable kernels < v6.6.