Subject: CVE-2024-49905: drm/amd/display: Add null check for 'afb' in amdgpu_dm_plane_handle_cursor_update (v2)

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

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

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

drm/amd/display: Add null check for 'afb' in amdgpu_dm_plane_handle_cursor_update (v2)

This commit adds a null check for the 'afb' variable in the
amdgpu_dm_plane_handle_cursor_update function. Previously, 'afb' was
assumed to be null, but was used later in the code without a null check.
This could potentially lead to a null pointer dereference.

Changes since v1:
- Moved the null check for 'afb' to the line where 'afb' is used. (Alex)

Fixes the below:
drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_plane.c:1298 amdgpu_dm_plane_handle_cursor_update() error: we previously assumed 'afb' could be null (see line 1252)

The Linux kernel CVE team has assigned CVE-2024-49905 to this issue.

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

	Fixed in 6.1.113 with commit bd0e24e5e608
	Fixed in 6.6.55 with commit 75839e2365b6
	Fixed in 6.10.14 with commit 9132882eaae4
	Fixed in 6.11.3 with commit e4e26cbe34d7
	Fixed in 6.12-rc1 with commit cd9e9e0852d5

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-2024-49905
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_plane.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/bd0e24e5e608ccb9fdda300bb974496d6d8cf57d
	https://git.kernel.org/stable/c/75839e2365b666ff4e1b9047e442cab138eac4f6
	https://git.kernel.org/stable/c/9132882eaae4d21d2fc5843b3308379a481ebdf0
	https://git.kernel.org/stable/c/e4e26cbe34d7c1c1db5fb7b3101573c29866439f
	https://git.kernel.org/stable/c/cd9e9e0852d501f169aa3bb34e4b413d2eb48c37