linux-cve-announce - CVE-2024-44956: drm/xe/preempt_fence: enlarge the fence critical section

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Message-ID: <2024090412-CVE-2024-44956-8bcf@gregkh>
Date: Wed,  4 Sep 2024 20:36:16 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-44956: drm/xe/preempt_fence: enlarge the fence critical section

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

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

drm/xe/preempt_fence: enlarge the fence critical section

It is really easy to introduce subtle deadlocks in
preempt_fence_work_func() since we operate on single global ordered-wq
for signalling our preempt fences behind the scenes, so even though we
signal a particular fence, everything in the callback should be in the
fence critical section, since blocking in the callback will prevent
other published fences from signalling. If we enlarge the fence critical
section to cover the entire callback, then lockdep should be able to
understand this better, and complain if we grab a sensitive lock like
vm->lock, which is also held when waiting on preempt fences.

The Linux kernel CVE team has assigned CVE-2024-44956 to this issue.

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

	Fixed in 6.10.5 with commit 458bb83119df
	Fixed in 6.11-rc1 with commit 3cd1585e5790

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-2024-44956
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/xe/xe_preempt_fence.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/458bb83119dfee5d14c677f7846dd9363817006f
	https://git.kernel.org/stable/c/3cd1585e57908b6efcd967465ef7685f40b2a294