Subject: CVE-2021-47560: mlxsw: spectrum: Protect driver from buggy firmware

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

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

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

mlxsw: spectrum: Protect driver from buggy firmware

When processing port up/down events generated by the device's firmware,
the driver protects itself from events reported for non-existent local
ports, but not the CPU port (local port 0), which exists, but lacks a
netdev.

This can result in a NULL pointer dereference when calling
netif_carrier_{on,off}().

Fix this by bailing early when processing an event reported for the CPU
port. Problem was only observed when running on top of a buggy emulator.

The Linux kernel CVE team has assigned CVE-2021-47560 to this issue.

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

	Issue introduced in 5.4 with commit 28b1987ef506 and fixed in 5.10.83 with commit 90d0736876c5
	Issue introduced in 5.4 with commit 28b1987ef506 and fixed in 5.15.6 with commit da4d70199e5d
	Issue introduced in 5.4 with commit 28b1987ef506 and fixed in 5.16 with commit 63b08b1f6834

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-2021-47560
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/net/ethernet/mellanox/mlxsw/spectrum.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/90d0736876c50ecde1a3275636a06b9ddb1cace9
	https://git.kernel.org/stable/c/da4d70199e5d82da664a80077508d6c18f5e76df
	https://git.kernel.org/stable/c/63b08b1f6834bbb0b4f7783bf63b80c8c8e9a047