CVE-2026-68256: drm/amd/display: detect_link_and_local_sink: DP alt mode timeout path leaks prev_sink reference

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

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

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

drm/amd/display: detect_link_and_local_sink: DP alt mode timeout path leaks prev_sink reference

prev_sink is unconditionally retained via dc_sink_retain at function
  entry, but the DP alt mode timeout path inside SIGNAL_TYPE_DISPLAY_PORT
  returns false without releasing prev_sink. All other return paths in the
  function correctly call dc_sink_release(prev_sink), making this the only
  missing cleanup.

(cherry picked from commit 45510cf662dcf46b5d8926d454f338809f107b9d)

The Linux kernel CVE team has assigned CVE-2026-68256 to this issue.


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

	Issue introduced in 6.3 with commit 54618888d1ea7a26f8bccfb89e3c2420350c8047 and fixed in 6.6.148 with commit f9922828a4ebd26286fbe0286cc61695e7d9b07b
	Issue introduced in 6.3 with commit 54618888d1ea7a26f8bccfb89e3c2420350c8047 and fixed in 6.12.101 with commit a59e493567d18ef3858be9368acd132a01ebfa09
	Issue introduced in 6.3 with commit 54618888d1ea7a26f8bccfb89e3c2420350c8047 and fixed in 6.18.42 with commit 4ee77643e6194f2deb62fe62f04396f9825e27d8
	Issue introduced in 6.3 with commit 54618888d1ea7a26f8bccfb89e3c2420350c8047 and fixed in 7.1.6 with commit 58ea24dd96848626039296e9e8510270ec8dc4bf
	Issue introduced in 6.3 with commit 54618888d1ea7a26f8bccfb89e3c2420350c8047 and fixed in 7.2-rc2 with commit a6e14b976be48eebd8769cb5b883a6af7fc5ade1

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-2026-68256
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/dc/link/link_detection.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/f9922828a4ebd26286fbe0286cc61695e7d9b07b
	https://git.kernel.org/stable/c/a59e493567d18ef3858be9368acd132a01ebfa09
	https://git.kernel.org/stable/c/4ee77643e6194f2deb62fe62f04396f9825e27d8
	https://git.kernel.org/stable/c/58ea24dd96848626039296e9e8510270ec8dc4bf
	https://git.kernel.org/stable/c/a6e14b976be48eebd8769cb5b883a6af7fc5ade1