Subject: CVE-2021-46920: dmaengine: idxd: Fix clobbering of SWERR overflow bit on writeback

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

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

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

dmaengine: idxd: Fix clobbering of SWERR overflow bit on writeback

Current code blindly writes over the SWERR and the OVERFLOW bits. Write
back the bits actually read instead so the driver avoids clobbering the
OVERFLOW bit that comes after the register is read.

The Linux kernel CVE team has assigned CVE-2021-46920 to this issue.

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

	Issue introduced in 5.6 with commit bfe1d56091c1 and fixed in 5.10.32 with commit a5ad12d5d69c
	Issue introduced in 5.6 with commit bfe1d56091c1 and fixed in 5.11.16 with commit 02981a44a0e4
	Issue introduced in 5.6 with commit bfe1d56091c1 and fixed in 5.12 with commit ea941ac294d7

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-2021-46920
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/dma/idxd/irq.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/a5ad12d5d69c63af289a37f05187a0c6fe93553d
	https://git.kernel.org/stable/c/02981a44a0e402089775416371bd2e0c935685f8
	https://git.kernel.org/stable/c/ea941ac294d75d0ace50797aebf0056f6f8f7a7f