Subject: CVE-2021-47471: drm: mxsfb: Fix NULL pointer dereference crash on unload

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

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

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

drm: mxsfb: Fix NULL pointer dereference crash on unload

The mxsfb->crtc.funcs may already be NULL when unloading the driver,
in which case calling mxsfb_irq_disable() via drm_irq_uninstall() from
mxsfb_unload() leads to NULL pointer dereference.

Since all we care about is masking the IRQ and mxsfb->base is still
valid, just use that to clear and mask the IRQ.

The Linux kernel CVE team has assigned CVE-2021-47471 to this issue.

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

	Issue introduced in 5.10 with commit ae1ed0093281 and fixed in 5.10.76 with commit f40c2281d2c0
	Issue introduced in 5.10 with commit ae1ed0093281 and fixed in 5.14.15 with commit b0e6db0656dd
	Issue introduced in 5.10 with commit ae1ed0093281 and fixed in 5.15 with commit 3cfc183052c3

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-2021-47471
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/mxsfb/mxsfb_drv.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/f40c2281d2c0674d32ba732fee45222d76495472
	https://git.kernel.org/stable/c/b0e6db0656ddfd8bb57303c2ef61ee1c1cc694a8
	https://git.kernel.org/stable/c/3cfc183052c3dbf8eae57b6c1685dab00ed3db4a