Subject: CVE-2024-49919: drm/amd/display: Add null check for head_pipe in dcn201_acquire_free_pipe_for_layer

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

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

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

drm/amd/display: Add null check for head_pipe in dcn201_acquire_free_pipe_for_layer

This commit addresses a potential null pointer dereference issue in the
`dcn201_acquire_free_pipe_for_layer` function. The issue could occur
when `head_pipe` is null.

The fix adds a check to ensure `head_pipe` is not null before asserting
it. If `head_pipe` is null, the function returns NULL to prevent a
potential null pointer dereference.

Reported by smatch:
drivers/gpu/drm/amd/amdgpu/../display/dc/resource/dcn201/dcn201_resource.c:1016 dcn201_acquire_free_pipe_for_layer() error: we previously assumed 'head_pipe' could be null (see line 1010)

The Linux kernel CVE team has assigned CVE-2024-49919 to this issue.

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

	Fixed in 6.10.14 with commit 390d757621f5
	Fixed in 6.11.3 with commit 8a1b1655a490
	Fixed in 6.12-rc1 with commit f22f4754aaa4

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-2024-49919
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/resource/dcn201/dcn201_resource.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/390d757621f5f35d11a63ed7d9d3262ead240064
	https://git.kernel.org/stable/c/8a1b1655a490a492a5a6987254c935ecce4eb9de
	https://git.kernel.org/stable/c/f22f4754aaa47d8c59f166ba3042182859e5dff7