linux-cve-announce - CVE-2026-23034: drm/amdgpu/userq: Fix fence reference leak on queue teardown v2

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Message-ID: <2026013121-CVE-2026-23034-9a60@gregkh>
Date: Sat, 31 Jan 2026 12:44:34 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2026-23034: drm/amdgpu/userq: Fix fence reference leak on queue teardown v2

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

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->last_fence. This pointer holds an extra dma_fence 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 dma_fence_put(), the last fence object can stay
alive when the driver unloads. This leaves an allocated object in the
amdgpu_userq_fence slab cache and triggers

This is visible during driver unload as:

  BUG amdgpu_userq_fence: Objects remaining on __kmem_cache_shutdown()
  kmem_cache_destroy amdgpu_userq_fence: Slab cache still has objects
  Call Trace:
    kmem_cache_destroy
    amdgpu_userq_fence_slab_fini
    amdgpu_exit
    __do_sys_delete_module

Fix this by putting userq->last_fence and clearing the pointer during
amdgpu_userq_fence_driver_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->last_fence with dma_fence_put()
    (Christian)

(cherry picked from commit 8e051e38a8d45caf6a866d4ff842105b577953bb)

The Linux kernel CVE team has assigned CVE-2026-23034 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.16 with commit edc762a51c7181d6fe1e0837e2eb69afb406f98e and fixed in 6.18.7 with commit e1a30e1ab33fc522785d04bbf7e1b13a5c5c9175
	Issue introduced in 6.16 with commit edc762a51c7181d6fe1e0837e2eb69afb406f98e and fixed in 6.19-rc6 with commit b2426a211dba6432e32a2e70e9183c6e134475c6

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-23034
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/e1a30e1ab33fc522785d04bbf7e1b13a5c5c9175
	https://git.kernel.org/stable/c/b2426a211dba6432e32a2e70e9183c6e134475c6