Subject: CVE-2024-46850: drm/amd/display: Avoid race between dcn35_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 dcn35_set_drr() and dc_state_destruct()

dc_state_destruct() nulls the resource context of the DC state. The pipe
context passed to dcn35_set_drr() is a member of this resource context.

If dc_state_destruct() is called parallel to the IRQ processing (which
calls dcn35_set_drr() at some point), we can end up using already nulled
function callback fields of struct stream_resource.

The logic in dcn35_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 0607a50c004798a96e62c089a4c34c220179dcb5)

The Linux kernel CVE team has assigned CVE-2024-46850 to this issue.

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

	Issue introduced in 6.7 with commit 06ad7e164256 and fixed in 6.10.11 with commit 42850927656a
	Issue introduced in 6.7 with commit 06ad7e164256 and fixed in 6.11 with commit e835d5144f5e

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-2024-46850
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/dcn35/dcn35_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/42850927656a540428e58d370b3c1599a617bac7
	https://git.kernel.org/stable/c/e835d5144f5ef78e4f8828c63e2f0d61144f283a