CVE-2024-56549 cachefiles: Fix NULL pointer dereference in object->file
A race condition in the Linux kernel's cachefiles module causes a NULL pointer dereference, leading to 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-2024-56549?
CVE-2024-56549 is a high-severity vulnerability in Linux kernel, published on 27 Dec 2024. 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:
cachefiles: Fix NULL pointer dereference in object->file
At present, the object->file has the NULL pointer dereference problem in ondemand-mode. The root cause is that the allocated fd and object->file lifetime are inconsistent, and the user-space invocation to anon_fd uses object->file. Following is the process that triggers the issue:
[write fd] [umount] cachefiles_ondemand_fd_write_iter fscache_cookie_state_machine cachefiles_withdraw_cookie if (!file) return -ENOBUFS cachefiles_clean_up_object cachefiles_unmark_inode_in_use fput(object->file) object->file = NULL // file NULL pointer dereference! __cachefiles_write(..., file, ...)
Fix this issue by add an additional reference count to the object->file before write/llseek, and decrement after it finished.
Weakness: CWE-476
Which versions are affected by CVE-2024-56549?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-56549?
Apply the vendor's patch.
Is CVE-2024-56549 being exploited?
There is no known exploitation of CVE-2024-56549 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-55195, BELL-CVE-2024-56549, DEBIAN-CVE-2024-56549, GHSA-hm4v-3pg5-6f5c, UBUNTU-CVE-2024-56549.