CVE-2024-57924 fs: relax assertions on failure to encode file handles
A local attacker can trigger a kernel assertion failure via specific filesystem operations, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-57924?
CVE-2024-57924 is a medium-severity denial of service vulnerability in Linux kernel, published on 19 Jan 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-617
Which versions are affected by CVE-2024-57924?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-57924?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2024-57924 being exploited?
There is no known exploitation of CVE-2024-57924 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-67842, BELL-CVE-2024-57924, DEBIAN-CVE-2024-57924, GHSA-f344-cfpj-cvmx, ROOT-OS-DEBIAN-11-CVE-2024-57924, ROOT-OS-DEBIAN-12-CVE-2024-57924 and 2 more.