CVE-2025-21911: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-21911 is a vulnerability discovered in the Linux kernel affecting the DRM/Imagination subsystem, specifically related to deadlock issues in fence release processing. The vulnerability was disclosed on April 1, 2025, and affects Linux kernel versions from 6.13 up to 6.13.7, as well as release candidates 6.14-rc1 through 6.14-rc5 (NVD).

The vulnerability stems from improper locking mechanisms in the DRM/Imagination driver, specifically during fence release processing. The issue manifests as a recursive locking scenario where a task attempts to acquire a lock (reservationwwclass_mutex) while already holding the same lock, leading to a deadlock condition. The vulnerability has been assigned a CVSS v3.1 base score of 5.5 (MEDIUM) with a vector string of CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H, indicating local access requirements and potential high impact on system availability (NVD).

The vulnerability can result in system deadlocks, potentially causing system hangs or reduced availability of the affected system. The CVSS scoring indicates no impact on confidentiality or integrity, but a high impact on system availability (NVD).

The vulnerability has been resolved by modifying the scheduler queue fence release processing to operate on a workqueue rather than in the release function itself. Patches have been made available through the Linux kernel repository (Kernel Patch 1, Kernel Patch 2, Kernel Patch 3).