CVE-2026-68364: drm/amd/display: Fix ISM dc_lock deadlock during suspend

From: Greg Kroah-Hartman <[email protected]>

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

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

drm/amd/display: Fix ISM dc_lock deadlock during suspend

[Why]
System hang observed during suspend/resume while video is playing.
amdgpu_dm_ism_disable() is called under dc_lock and waits for ISM
delayed work via disable_delayed_work_sync(). The work handlers
themselves take dc_lock, producing an ABBA deadlock when a worker is
in flight at suspend time.

[How]
Split the disable path into two phases with opposite locking
contracts:
  1. amdgpu_dm_ism_disable() -- quiesces workers, must NOT hold
     dc_lock.
  2. amdgpu_dm_ism_force_full_power() (new) -- drives the ISM FSM
     back to FULL_POWER_RUNNING, must hold dc_lock.

The Linux kernel CVE team has assigned CVE-2026-68364 to this issue.


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

	Fixed in 7.1.6 with commit 95776812e6b8f908563e8994d5d947b68baf68a6
	Fixed in 7.2-rc1 with commit 3714fe242592e3699ac5e2c19d68b275a210be7d

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-2026-68364
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/display/amdgpu_dm/amdgpu_dm.c
	drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_ism.c
	drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_ism.h


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/95776812e6b8f908563e8994d5d947b68baf68a6
	https://git.kernel.org/stable/c/3714fe242592e3699ac5e2c19d68b275a210be7d