CVE-2026-68241: drm/i915/mst: limit DP MST ESI service loop

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

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

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

drm/i915/mst: limit DP MST ESI service loop

The loop in intel_dp_check_mst_status() keeps servicing interrupts
originating from the sink without bound. Add an upper bound to the new
interrupts occurring during interrupt processing to not get stuck on
potentially stuck sink devices. Use arbitrary 32 tries to clear incoming
interrupts in one go.

Discovered using AI-assisted static analysis confirmed by Intel Product
Security.

Note: The condition likely pre-dates the commit in the Fixes: tag, but
this is about as far back as a backport has any chance of
succeeding. Before that, the retry had a goto.

(cherry picked from commit b4ea5272133059acb493cc36599071a9e852ec2e)

The Linux kernel CVE team has assigned CVE-2026-68241 to this issue.


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

	Issue introduced in 5.8 with commit 3c0ec2c2d5948356a22c8f1c08a8087b12a303e7 and fixed in 6.18.42 with commit e3bcd3bf7eeca9570b9fa0b2f8a602c7bcc6b0d0
	Issue introduced in 5.8 with commit 3c0ec2c2d5948356a22c8f1c08a8087b12a303e7 and fixed in 7.1.6 with commit 9061fbf2230b6fcef042a6f637beae57c2fc93a5
	Issue introduced in 5.8 with commit 3c0ec2c2d5948356a22c8f1c08a8087b12a303e7 and fixed in 7.2-rc3 with commit 005771c18c5b2c98cb4e7517661aea460990fd3f

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-2026-68241
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/i915/display/intel_dp.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/e3bcd3bf7eeca9570b9fa0b2f8a602c7bcc6b0d0
	https://git.kernel.org/stable/c/9061fbf2230b6fcef042a6f637beae57c2fc93a5
	https://git.kernel.org/stable/c/005771c18c5b2c98cb4e7517661aea460990fd3f