CVE-2025-21807 block: fix queue freeze vs limits lock order in sysfs store methods
A race condition in the Linux kernel block layer can cause a deadlock when modifying queue limits, 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-2025-21807?
CVE-2025-21807 is a medium-severity vulnerability in Linux kernel, published on 27 Feb 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:
block: fix queue freeze vs limits lock order in sysfs store methods
queue_attr_store() always freezes a device queue before calling the attribute store operation. For attributes that control queue limits, the store operation will also lock the queue limits with a call to queue_limits_start_update(). However, some drivers (e.g. SCSI sd) may need to issue commands to a device to obtain limit values from the hardware with the queue limits locked. This creates a potential ABBA deadlock situation if a user attempts to modify a limit (thus freezing the device queue) while the device driver starts a revalidation of the device queue limits.
Avoid such deadlock by not freezing the queue before calling the ->store_limit() method in struct queue_sysfs_entry and instead use the queue_limits_commit_update_frozen helper to freeze the queue after taking the limits lock.
This also removes taking the sysfs lock for the store_limit method as it doesn't protect anything here, but creates even more nesting. Hopefully it will go away from the actual sysfs methods entirely soon.
(commit log adapted from a similar patch from Damien Le Moal)
Weakness: CWE-667
Which versions are affected by CVE-2025-21807?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21807?
Apply the vendor's patch.
Is CVE-2025-21807 being exploited?
There is no known exploitation of CVE-2025-21807 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-21807, DEBIAN-CVE-2025-21807, GHSA-cp43-x3rr-gwcc, ROOT-OS-DEBIAN-13-CVE-2025-21807, UBUNTU-CVE-2025-21807.