Subject: CVE-2021-47573: xen/blkfront: harden blkfront against event channel storms

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

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

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

xen/blkfront: harden blkfront against event channel storms

The Xen blkfront driver is still vulnerable for an attack via excessive
number of events sent by the backend. Fix that by using lateeoi event
channels.

This is part of XSA-391

The Linux kernel CVE team has assigned CVE-2021-47573 to this issue.

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

	Fixed in 4.4.296 with commit 3e04b9e6aa7d
	Fixed in 4.9.294 with commit 25898389795b
	Fixed in 4.14.259 with commit 5ac3b68b79c9
	Fixed in 4.19.222 with commit 269d7124bcfa
	Fixed in 5.4.168 with commit 4ed9f5c511ce
	Fixed in 5.10.88 with commit 8ac3b6ee7c9f
	Fixed in 5.15.11 with commit caf9b51829a5
	Fixed in 5.16 with commit 0fd08a34e8e3

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-2021-47573
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/block/xen-blkfront.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/3e04b9e6aa7d77287e70a400be83060d2b7b2cfe
	https://git.kernel.org/stable/c/25898389795bd85d8e1520c0c75c3ad906c17da7
	https://git.kernel.org/stable/c/5ac3b68b79c9e964dd6f3cf80ff825518e502b79
	https://git.kernel.org/stable/c/269d7124bcfad2558d2329d0fe603ca20b20d3f4
	https://git.kernel.org/stable/c/4ed9f5c511ce95cb8db05ff82026ea901f45fd76
	https://git.kernel.org/stable/c/8ac3b6ee7c9ff2df7c99624bb1235e2e55623825
	https://git.kernel.org/stable/c/caf9b51829a50590b84daea924a0fd62d32bc952
	https://git.kernel.org/stable/c/0fd08a34e8e3b67ec9bd8287ac0facf8374b844a