CVE-2026-68382: drm/xe/guc: Hold device ref until queue teardown completes

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

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

drm/xe/guc: Hold device ref until queue teardown completes

GuC exec queue destruction can run asynchronously. If the final device
put happens from a destroy worker, drmm cleanup can end up draining
the same workqueue and deadlock.

Hold a drm_device reference for the queue lifetime and drop it after
queue teardown completes. This keeps drmm cleanup from running while
async destroy work is still pending.

Move GuC destroy work to a module-lifetime Xe workqueue and flush it
on PCI remove so hot-unbind/rebind still waits for pending destroy work.

With queue-held device refs, guc_submit_sw_fini() cannot run with live
GuC IDs. Replace the fini wait with an assertion and remove the unused
fini_wq.

v2:
  - Rebase

v3:
  - Switch to queue-lifetime drm_dev_get()/drm_dev_put() model. (Matt)
  - Queue async teardown on system_dfl_wq instead of xe->destroy_wq. (Matt)
  - Drop separate deferred drm_dev_put worker.
  - Remove stale drain_workqueue(xe->destroy_wq) from guc_submit_sw_fini().

v4:
  - Replace the guc_submit_sw_fini() wait with an assertion and remove
    the now-unused fini_wq. (sashiko)

v5:
  - Move destroy work to a module-lifetime Xe workqueue instead of
    system_dfl_wq. (Matt)
  - Flush the module-lifetime destroy workqueue during PCI remove to
    preserve the old device-remove wait semantics.

v6:
  - Keep SVM pagemap destroy work on the per-device destroy_wq to avoid
    letting it outlive the xe_device/drm_device. (Sashiko)
  - Use WQ_MEM_RECLAIM for xe->destroy_wq because SVM pagemap destroy work
    can be queued from the reclaim path.

v7:
  - Drop the per-device xe->destroy_wq and use the module-level destroy WQ
    for SVM pagemap destroy as well. (Matt)
  - Rename xe_exec_queue_destroy_wq_*() helpers to xe_destroy_wq_*()
    helpers because the WQ is no longer exec-queue specific. (Matt)

v8:
  - Rebase.

v9:
  - Keep SVM pagemap destroy work on the per-device WQ_MEM_RECLAIM
    destroy_wq because it can be queued from reclaim and embeds
    the dev_pagemap used by devres teardown. (Sashiko)
  - Keep the module-level destroy WQ GuC-only and drop WQ_MEM_RECLAIM
    from it.
  - Update the module-WQ kdoc to document the GuC/SVM split.

v10:
  - Keep xe->destroy_wq per-cpu while adding WQ_MEM_RECLAIM to fix the
    workqueue allocation warning.

v11:
  - Drop the SVM pagemap destroy comment as it was revision-specific.
    (Thomas)

v12:
  - Rebase.

(cherry picked from commit da1124abac689cc2b1d8995e5f0a816f8a122edb)

The Linux kernel CVE team has assigned CVE-2026-68382 to this issue.


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

	Issue introduced in 6.12 with commit 2d2be279f1ca9e7288282d4214f16eea8a727cdb and fixed in 7.1.6 with commit 03d6f83979b0d75a0b0893dfe1735ec93facf515
	Issue introduced in 6.12 with commit 2d2be279f1ca9e7288282d4214f16eea8a727cdb and fixed in 7.2-rc4 with commit 9b7e60184f4b22e893d4ae95234d5f26261a430c
	Issue introduced in 6.10.14 with commit 272b0e78874586d6ccae04079d75b27b47705544
	Issue introduced in 6.11.3 with commit 421c74670b0f9d5c007f1276d3647aa58f407fde

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-2026-68382
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/xe/xe_device.c
	drivers/gpu/drm/xe/xe_device_types.h
	drivers/gpu/drm/xe/xe_guc_submit.c
	drivers/gpu/drm/xe/xe_guc_types.h
	drivers/gpu/drm/xe/xe_module.c
	drivers/gpu/drm/xe/xe_module.h
	drivers/gpu/drm/xe/xe_pci.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/03d6f83979b0d75a0b0893dfe1735ec93facf515
	https://git.kernel.org/stable/c/9b7e60184f4b22e893d4ae95234d5f26261a430c