Executive brief
A synchronization issue was identified in the Linux kernel's graphics subsystem (DRM) specifically affecting shared memory (shmem) testing components. While primarily impacting internal kernel tests, such flaws in memory management can lead to system instability or unexpected behavior. The issue has been resolved by ensuring proper locking mechanisms are used during memory mapping operations.
Technical details
This vulnerability stems from a locking inconsistency in the Direct Rendering Manager (DRM) shmem helper. Specifically, Kunit tests were utilizing 'vmap_locked' and 'vunmap_locked' functions without actually holding the GEM object's reservation lock (dma_resv). This resulted in kernel warnings at 'drm_gem_shmem_vmap_locked', 'drm_gem_shmem_pin_locked', and 'drm_gem_shmem_get_pages_locked'. The fix introduces new Kunit-specific wrappers, 'drm_gem_shmem_vmap' and 'drm_gem_shmem_vunmap', which correctly acquire and release the dma_resv lock around the underlying locked operations. This issue primarily affects kernel testing environments (CONFIG_KUNIT) rather than production driver interfaces.
Affected products
- Linux Linux Kernel v6.16+
Timeline
- 2025-12-12: other: Patch authored
- 2026-05-08: disclosed: CVE published