CVE-2026-23034

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

drm/amdgpu/userq: Fix fence reference leak on queue teardown v2

The user mode queue keeps a pointer to the most recent fence in userq->lastfence. This pointer holds an extra dmafence reference.

When the queue is destroyed, we free the fence driver and its xarray, but we forgot to drop the last_fence reference.

Because of the missing dmafenceput(), the last fence object can stay alive when the driver unloads. This leaves an allocated object in the amdgpuuserqfence slab cache and triggers

This is visible during driver unload as:

BUG amdgpuuserqfence: Objects remaining on __kmemcacheshutdown() kmem_cachedestroy amdgpuuserqfence: Slab cache still has objects Call Trace: kmemcachedestroy amdgpuuserqfenceslabfini amdgpuexit _dosysdeletemodule

Fix this by putting userq->lastfence and clearing the pointer during amdgpuuserqfencedriver_free().

This makes sure the fence reference is released and the slab cache is empty when the module exits.

v2: Update to only release userq->lastfence with dmafence_put() (Christian)

(cherry picked from commit 8e051e38a8d45caf6a866d4ff842105b577953bb)