cve/published/2023/CVE-2023-52981.mbox

From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: <linux-cve-announce@vger.kernel.org>
Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
Subject: CVE-2023-52981: drm/i915: Fix request ref counting during error capture & debugfs dump

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

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

drm/i915: Fix request ref counting during error capture & debugfs dump

When GuC support was added to error capture, the reference counting
around the request object was broken. Fix it up.

The context based search manages the spinlocking around the search
internally. So it needs to grab the reference count internally as
well. The execlist only request based search relies on external
locking, so it needs an external reference count but within the
spinlock not outside it.

The only other caller of the context based search is the code for
dumping engine state to debugfs. That code wasn't previously getting
an explicit reference at all as it does everything while holding the
execlist specific spinlock. So, that needs updaing as well as that
spinlock doesn't help when using GuC submission. Rather than trying to
conditionally get/put depending on submission model, just change it to
always do the get/put.

v2: Explicitly document adding an extra blank line in some dense code
(Andy Shevchenko). Fix multiple potential null pointer derefs in case
of no request found (some spotted by Tvrtko, but there was more!).
Also fix a leaked request in case of !started and another in
__guc_reset_context now that intel_context_find_active_request is
actually reference counting the returned request.
v3: Add a _get suffix to intel_context_find_active_request now that it
grabs a reference (Daniele).
v4: Split the intel_guc_find_hung_context change to a separate patch
and rename intel_context_find_active_request_get to
intel_context_get_active_request (Tvrtko).
v5: s/locking/reference counting/ in commit message (Tvrtko)

(cherry picked from commit 3700e353781e27f1bc7222f51f2cc36cbeb9b4ec)

The Linux kernel CVE team has assigned CVE-2023-52981 to this issue.


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

	Issue introduced in 5.15 with commit 573ba126aef37c8315e5bb68d2dad515efa96994 and fixed in 6.1.11 with commit 9467397f417dd7b5d0db91452f0474e79716a527
	Issue introduced in 5.15 with commit 573ba126aef37c8315e5bb68d2dad515efa96994 and fixed in 6.2 with commit 86d8ddc74124c3fdfc139f246ba6da15e45e86e3

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-2023-52981
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/i915/gt/intel_context.c
	drivers/gpu/drm/i915/gt/intel_context.h
	drivers/gpu/drm/i915/gt/intel_engine_cs.c
	drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
	drivers/gpu/drm/i915/i915_gpu_error.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/9467397f417dd7b5d0db91452f0474e79716a527
	https://git.kernel.org/stable/c/86d8ddc74124c3fdfc139f246ba6da15e45e86e3