linux-cve-announce - CVE-2022-49203: drm/amd/display: Fix double free during GPU reset on DC streams

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Message-ID: <2025022618-CVE-2022-49203-48ec@gregkh>
Date: Wed, 26 Feb 2025 02:56:48 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49203: drm/amd/display: Fix double free during GPU reset on DC streams

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

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

drm/amd/display: Fix double free during GPU reset on DC streams

[Why]
The issue only occurs during the GPU reset code path.

We first backup the current state prior to commiting 0 streams
internally from DM to DC. This state backup contains valid link
encoder assignments.

DC will clear the link encoder assignments as part of current state
(but not the backup, since it was a copied before the commit) and
free the extra stream reference it held.

DC requires that the link encoder assignments remain cleared/invalid
prior to commiting. Since the backup still has valid assignments we
call the interface post reset to clear them. This routine also
releases the extra reference that the link encoder interface held -
resulting in a double free (and eventually a NULL pointer dereference).

[How]
We'll have to do a full DC commit anyway after GPU reset because
the stream count previously went to 0.

We don't need to retain the assignment that we had backed up, so
just copy off of the now clean current state assignment after the
reset has occcurred with the new link_enc_cfg_copy() interface.

The Linux kernel CVE team has assigned CVE-2022-49203 to this issue.

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

	Issue introduced in 5.17 with commit 6d63fcc2a334f7bd15e4e9b1db50a19335d2af4f and fixed in 5.17.2 with commit bbfcdd6289ba6f00f0cd7d496946dce9f6c600ac
	Issue introduced in 5.17 with commit 6d63fcc2a334f7bd15e4e9b1db50a19335d2af4f and fixed in 5.18 with commit 32685b32d825ca08c5dec826477332df886c4743

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-2022-49203
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/dc/core/dc_link_enc_cfg.c
	drivers/gpu/drm/amd/display/dc/inc/link_enc_cfg.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/bbfcdd6289ba6f00f0cd7d496946dce9f6c600ac
	https://git.kernel.org/stable/c/32685b32d825ca08c5dec826477332df886c4743