CVE-2025-21807: block: fix queue freeze vs limits lock order in sysfs store methods
In the Linux kernel, the following vulnerability has been resolved:
block: fix queue freeze vs limits lock order in sysfs store methods
queueattrstore() 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 queuelimitsstartupdate(). 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 ->storelimit() method in struct queuesysfsentry and instead use the queuelimitscommitupdatefrozen helper to freeze the queue after taking the limits lock.
This also removes taking the sysfs lock for the storelimit 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)
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2025-21807?
CVE-2025-21807 has a medium severity rating due to potential impacts on device queue management.
How do I fix CVE-2025-21807?
To fix CVE-2025-21807, update to the latest stable version of the Linux kernel that includes the patch.
Who is affected by CVE-2025-21807?
CVE-2025-21807 affects systems running specific versions of the Linux kernel that utilize queue attribute manipulation.
What are the potential consequences of CVE-2025-21807?
Potential consequences of CVE-2025-21807 include race conditions that could lead to system instability during device queue operations.
Is there a workaround for CVE-2025-21807?
There are no formal workarounds for CVE-2025-21807; updating the kernel is the recommended approach.