Subject: CVE-2024-43863: drm/vmwgfx: Fix a deadlock in dma buf fence polling

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

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

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

drm/vmwgfx: Fix a deadlock in dma buf fence polling

Introduce a version of the fence ops that on release doesn't remove
the fence from the pending list, and thus doesn't require a lock to
fix poll->fence wait->fence unref deadlocks.

vmwgfx overwrites the wait callback to iterate over the list of all
fences and update their status, to do that it holds a lock to prevent
the list modifcations from other threads. The fence destroy callback
both deletes the fence and removes it from the list of pending
fences, for which it holds a lock.

dma buf polling cb unrefs a fence after it's been signaled: so the poll
calls the wait, which signals the fences, which are being destroyed.
The destruction tries to acquire the lock on the pending fences list
which it can never get because it's held by the wait from which it
was called.

Old bug, but not a lot of userspace apps were using dma-buf polling
interfaces. Fix those, in particular this fixes KDE stalls/deadlock.

The Linux kernel CVE team has assigned CVE-2024-43863 to this issue.

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

	Issue introduced in 3.18 with commit 2298e804e96e and fixed in 5.15.165 with commit 9e20d028d8d1
	Issue introduced in 3.18 with commit 2298e804e96e and fixed in 6.1.104 with commit 3b933b16c996
	Issue introduced in 3.18 with commit 2298e804e96e and fixed in 6.6.45 with commit a8943969f9ea
	Issue introduced in 3.18 with commit 2298e804e96e and fixed in 6.10.4 with commit c98ab18b9f31
	Issue introduced in 3.18 with commit 2298e804e96e and fixed in 6.11 with commit e58337100721

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-2024-43863
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/vmwgfx/vmwgfx_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/9e20d028d8d1deb1e7fed18f22ffc01669cf3237
	https://git.kernel.org/stable/c/3b933b16c996af8adb6bc1b5748a63dfb41a82bc
	https://git.kernel.org/stable/c/a8943969f9ead2fd3044fc826140a21622ef830e
	https://git.kernel.org/stable/c/c98ab18b9f315ff977c2c65d7c71298ef98be8e3
	https://git.kernel.org/stable/c/e58337100721f3cc0c7424a18730e4f39844934f