Subject: CVE-2021-47604: vduse: check that offset is within bounds in get_config()

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

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

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

vduse: check that offset is within bounds in get_config()

This condition checks "len" but it does not check "offset" and that
could result in an out of bounds read if "offset > dev->config_size".
The problem is that since both variables are unsigned the
"dev->config_size - offset" subtraction would result in a very high
unsigned value.

I think these checks might not be necessary because "len" and "offset"
are supposed to already have been validated using the
vhost_vdpa_config_validate() function.  But I do not know the code
perfectly, and I like to be safe.

The Linux kernel CVE team has assigned CVE-2021-47604 to this issue.

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

	Issue introduced in 5.15 with commit c8a6153b6c59 and fixed in 5.15.11 with commit ebbbc5fea3f6
	Issue introduced in 5.15 with commit c8a6153b6c59 and fixed in 5.16 with commit dc1db0060c02

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-2021-47604
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/vdpa/vdpa_user/vduse_dev.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/ebbbc5fea3f648175df1aa3f127c78eb0252cc2a
	https://git.kernel.org/stable/c/dc1db0060c02d119fd4196924eff2d1129e9a442