Subject: CVE-2021-47172: iio: adc: ad7124: Fix potential overflow due to non sequential channel numbers

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

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

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

iio: adc: ad7124: Fix potential overflow due to non sequential channel numbers

Channel numbering must start at 0 and then not have any holes, or
it is possible to overflow the available storage.  Note this bug was
introduced as part of a fix to ensure we didn't rely on the ordering
of child nodes.  So we need to support arbitrary ordering but they all
need to be there somewhere.

Note I hit this when using qemu to test the rest of this series.
Arguably this isn't the best fix, but it is probably the most minimal
option for backporting etc.

Alexandru's sign-off is here because he carried this patch in a larger
set that Jonathan then applied.

The Linux kernel CVE team has assigned CVE-2021-47172 to this issue.

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

	Issue introduced in 5.4.14 with commit 5408cbc63373 and fixed in 5.4.124 with commit f49149964d24
	Issue introduced in 5.5 with commit d7857e4ee1ba and fixed in 5.10.42 with commit f70122825076
	Issue introduced in 5.5 with commit d7857e4ee1ba and fixed in 5.12.9 with commit 26da8040eccc
	Issue introduced in 5.5 with commit d7857e4ee1ba and fixed in 5.13 with commit f2a772c51206

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-2021-47172
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/iio/adc/ad7124.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/f49149964d2423fb618fb6b755bb1eaa431cca2c
	https://git.kernel.org/stable/c/f70122825076117787b91e7f219e21c09f11a5b9
	https://git.kernel.org/stable/c/26da8040eccc6c6b0e415e9a3baf72fd39eb2fdc
	https://git.kernel.org/stable/c/f2a772c51206b0c3f262e4f6a3812c89a650191b