linux-cve-announce - CVE-2024-56552: drm/xe/guc_submit: fix race around suspend

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Message-ID: <2024122710-CVE-2024-56552-aca0@gregkh>
Date: Fri, 27 Dec 2024 15:23:03 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-56552: drm/xe/guc_submit: fix race around suspend_pending

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

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

drm/xe/guc_submit: fix race around suspend_pending

Currently in some testcases we can trigger:

xe 0000:03:00.0: [drm] Assertion `exec_queue_destroyed(q)` failed!
....
WARNING: CPU: 18 PID: 2640 at drivers/gpu/drm/xe/xe_guc_submit.c:1826 xe_guc_sched_done_handler+0xa54/0xef0 [xe]
xe 0000:03:00.0: [drm] *ERROR* GT1: DEREGISTER_DONE: Unexpected engine state 0x00a1, guc_id=57

Looking at a snippet of corresponding ftrace for this GuC id we can see:

162.673311: xe_sched_msg_add:     dev=0000:03:00.0, gt=1 guc_id=57, opcode=3
162.673317: xe_sched_msg_recv:    dev=0000:03:00.0, gt=1 guc_id=57, opcode=3
162.673319: xe_exec_queue_scheduling_disable: dev=0000:03:00.0, 1:0x2, gt=1, width=1, guc_id=57, guc_state=0x29, flags=0x0
162.674089: xe_exec_queue_kill:   dev=0000:03:00.0, 1:0x2, gt=1, width=1, guc_id=57, guc_state=0x29, flags=0x0
162.674108: xe_exec_queue_close:  dev=0000:03:00.0, 1:0x2, gt=1, width=1, guc_id=57, guc_state=0xa9, flags=0x0
162.674488: xe_exec_queue_scheduling_done: dev=0000:03:00.0, 1:0x2, gt=1, width=1, guc_id=57, guc_state=0xa9, flags=0x0
162.678452: xe_exec_queue_deregister: dev=0000:03:00.0, 1:0x2, gt=1, width=1, guc_id=57, guc_state=0xa1, flags=0x0

It looks like we try to suspend the queue (opcode=3), setting
suspend_pending and triggering a disable_scheduling. The user then
closes the queue. However the close will also forcefully signal the
suspend fence after killing the queue, later when the G2H response for
disable_scheduling comes back we have now cleared suspend_pending when
signalling the suspend fence, so the disable_scheduling now incorrectly
tries to also deregister the queue. This leads to warnings since the queue
has yet to even be marked for destruction. We also seem to trigger
errors later with trying to double unregister the same queue.

To fix this tweak the ordering when handling the response to ensure we
don't race with a disable_scheduling that didn't actually intend to
perform an unregister.  The destruction path should now also correctly
wait for any pending_disable before marking as destroyed.

(cherry picked from commit f161809b362f027b6d72bd998e47f8f0bad60a2e)

The Linux kernel CVE team has assigned CVE-2024-56552 to this issue.

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

	Issue introduced in 6.8 with commit dd08ebf6c3525a7ea2186e636df064ea47281987 and fixed in 6.12.4 with commit 5ddcb50b700221fa7d7be2adcb3d7d7afe8633dd
	Issue introduced in 6.8 with commit dd08ebf6c3525a7ea2186e636df064ea47281987 and fixed in 6.13-rc1 with commit 87651f31ae4e6e6e7e6c7270b9b469405e747407

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-2024-56552
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_guc_submit.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/5ddcb50b700221fa7d7be2adcb3d7d7afe8633dd
	https://git.kernel.org/stable/c/87651f31ae4e6e6e7e6c7270b9b469405e747407