Subject: CVE-2024-46851: drm/amd/display: Avoid race between dcn10_set_drr() and dc_state_destruct()

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

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

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

drm/amd/display: Avoid race between dcn10_set_drr() and dc_state_destruct()

dc_state_destruct() nulls the resource context of the DC state. The pipe
context passed to dcn10_set_drr() is a member of this resource context.

If dc_state_destruct() is called parallel to the IRQ processing (which
calls dcn10_set_drr() at some point), we can end up using already nulled
function callback fields of struct stream_resource.

The logic in dcn10_set_drr() already tries to avoid this, by checking tg
against NULL. But if the nulling happens exactly after the NULL check and
before the next access, then we get a race.

Avoid this by copying tg first to a local variable, and then use this
variable for all the operations. This should work, as long as nobody
frees the resource pool where the timing generators live.

(cherry picked from commit a3cc326a43bdc48fbdf53443e1027a03e309b643)

The Linux kernel CVE team has assigned CVE-2024-46851 to this issue.

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

	Issue introduced in 6.7 with commit 06ad7e164256 and fixed in 6.10.11 with commit b6ce047a81f5
	Issue introduced in 6.7 with commit 06ad7e164256 and fixed in 6.11 with commit a7aeb03888b9

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-2024-46851
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/hwss/dcn10/dcn10_hwseq.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/b6ce047a81f508f5c60756db8dfb5ff486e4dad0
	https://git.kernel.org/stable/c/a7aeb03888b92304e2fc7d4d1c242f54a312561b