CVE-2025-38584

In the Linux kernel, the following vulnerability has been resolved:

padata: Fix pd UAF once and for all

There is a race condition/UAF in padata_reorder that goes back to the initial commit. A reference count is taken at the start of the process in padata_do_parallel, and released at the end in padata_serial_worker.

This reference count is (and only is) required for padata_replace to function correctly. If padata_replace is never called then there is no issue.

In the function padata_reorder which serves as the core of padata, as soon as padata is added to queue->serial.list, and the associated spin lock released, that padata may be processed and the reference count on pd would go away.

Fix this by getting the next padata before the squeue->serial lock is released.

In order to make this possible, simplify padata_reorder by only calling it once the next padata arrives.

The issue requires local access and the ability to trigger cachestat against shmem in specific race conditions, so Privileges Required = Low for the CVSS. Because of the high timing sensitivity, Attack Complexity = High. The impact is limited to Availability (A:H) since the bug can cause kernel crashes or DoS only.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.