linux-cve-announce - CVE-2024-35952: drm/ast: Fix soft lockup

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Message-ID: <2024052017-CVE-2024-35952-645b@gregkh>
Date: Mon, 20 May 2024 11:42:17 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-35952: drm/ast: Fix soft lockup

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

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

drm/ast: Fix soft lockup

There is a while-loop in ast_dp_set_on_off() that could lead to
infinite-loop. This is because the register, VGACRI-Dx, checked in
this API is a scratch register actually controlled by a MCU, named
DPMCU, in BMC.

These scratch registers are protected by scu-lock. If suc-lock is not
off, DPMCU can not update these registers and then host will have soft
lockup due to never updated status.

DPMCU is used to control DP and relative registers to handshake with
host's VGA driver. Even the most time-consuming task, DP's link
training, is less than 100ms. 200ms should be enough.

The Linux kernel CVE team has assigned CVE-2024-35952 to this issue.


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

	Issue introduced in 5.19 with commit 594e9c04b586 and fixed in 6.1.87 with commit 8a6fea3fcb57
	Issue introduced in 5.19 with commit 594e9c04b586 and fixed in 6.6.28 with commit a81b2acd43e2
	Issue introduced in 5.19 with commit 594e9c04b586 and fixed in 6.8.7 with commit 35768baf0fdf
	Issue introduced in 5.19 with commit 594e9c04b586 and fixed in 6.9 with commit bc004f503822

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-2024-35952
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/ast/ast_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/8a6fea3fcb577a543ef67683ca7105bde49a38fb
	https://git.kernel.org/stable/c/a81b2acd43e24e419f65df97348c76a5a1496066
	https://git.kernel.org/stable/c/35768baf0fdfc47ede42d899506bad78450e9294
	https://git.kernel.org/stable/c/bc004f5038220b1891ef4107134ccae44be55109