Subject: CVE-2021-47164: net/mlx5e: Fix null deref accessing lag dev

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

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

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

net/mlx5e: Fix null deref accessing lag dev

It could be the lag dev is null so stop processing the event.
In bond_enslave() the active/backup slave being set before setting the
upper dev so first event is without an upper dev.
After setting the upper dev with bond_master_upper_dev_link() there is
a second event and in that event we have an upper dev.

The Linux kernel CVE team has assigned CVE-2021-47164 to this issue.

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

	Issue introduced in 5.8 with commit 7e51891a237f and fixed in 5.10.42 with commit 2e4b0b95a489
	Issue introduced in 5.8 with commit 7e51891a237f and fixed in 5.12.9 with commit bdfd3593a824
	Issue introduced in 5.8 with commit 7e51891a237f and fixed in 5.13 with commit 83026d83186b

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-2021-47164
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/mlx5/core/en/rep/bond.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/2e4b0b95a489259f9d35a3db17023061f8f3d587
	https://git.kernel.org/stable/c/bdfd3593a8248eea6ecfcbf7b47b56b86515672d
	https://git.kernel.org/stable/c/83026d83186bc48bb41ee4872f339b83f31dfc55