Subject: CVE-2024-40976: drm/lima: mask irqs in timeout path before hard reset

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

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

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

drm/lima: mask irqs in timeout path before hard reset

There is a race condition in which a rendering job might take just long
enough to trigger the drm sched job timeout handler but also still
complete before the hard reset is done by the timeout handler.
This runs into race conditions not expected by the timeout handler.
In some very specific cases it currently may result in a refcount
imbalance on lima_pm_idle, with a stack dump such as:

[10136.669170] WARNING: CPU: 0 PID: 0 at drivers/gpu/drm/lima/lima_devfreq.c:205 lima_devfreq_record_idle+0xa0/0xb0
...
[10136.669459] pc : lima_devfreq_record_idle+0xa0/0xb0
...
[10136.669628] Call trace:
[10136.669634]  lima_devfreq_record_idle+0xa0/0xb0
[10136.669646]  lima_sched_pipe_task_done+0x5c/0xb0
[10136.669656]  lima_gp_irq_handler+0xa8/0x120
[10136.669666]  __handle_irq_event_percpu+0x48/0x160
[10136.669679]  handle_irq_event+0x4c/0xc0

We can prevent that race condition entirely by masking the irqs at the
beginning of the timeout handler, at which point we give up on waiting
for that job entirely.
The irqs will be enabled again at the next hard reset which is already
done as a recovery by the timeout handler.

The Linux kernel CVE team has assigned CVE-2024-40976 to this issue.

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

	Fixed in 5.10.221 with commit 03e7b2f7ae4c
	Fixed in 5.15.162 with commit 70aa1f2dec46
	Fixed in 6.1.96 with commit 9fd8ddd23793
	Fixed in 6.6.36 with commit bdbc4ca77f5e
	Fixed in 6.9.7 with commit 58bfd311c93d
	Fixed in 6.10 with commit a421cc7a6a00

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-2024-40976
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/lima/lima_sched.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/03e7b2f7ae4c0ae5fb8e4e2454ba4008877f196a
	https://git.kernel.org/stable/c/70aa1f2dec46b6fdb5f6b9f37b6bfa4a4dee0d3a
	https://git.kernel.org/stable/c/9fd8ddd23793a50dbcd11c6ba51f437f1ea7d344
	https://git.kernel.org/stable/c/bdbc4ca77f5eaac15de7230814253cddfed273b1
	https://git.kernel.org/stable/c/58bfd311c93d66d8282bf21ebbf35cc3bb8ad9db
	https://git.kernel.org/stable/c/a421cc7a6a001b70415aa4f66024fa6178885a14