Subject: CVE-2024-46857: net/mlx5: Fix bridge mode operations when there are no VFs

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

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

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

net/mlx5: Fix bridge mode operations when there are no VFs

Currently, trying to set the bridge mode attribute when numvfs=0 leads to a
crash:

bridge link set dev eth2 hwmode vepa

[  168.967392] BUG: kernel NULL pointer dereference, address: 0000000000000030
[...]
[  168.969989] RIP: 0010:mlx5_add_flow_rules+0x1f/0x300 [mlx5_core]
[...]
[  168.976037] Call Trace:
[  168.976188]  <TASK>
[  168.978620]  _mlx5_eswitch_set_vepa_locked+0x113/0x230 [mlx5_core]
[  168.979074]  mlx5_eswitch_set_vepa+0x7f/0xa0 [mlx5_core]
[  168.979471]  rtnl_bridge_setlink+0xe9/0x1f0
[  168.979714]  rtnetlink_rcv_msg+0x159/0x400
[  168.980451]  netlink_rcv_skb+0x54/0x100
[  168.980675]  netlink_unicast+0x241/0x360
[  168.980918]  netlink_sendmsg+0x1f6/0x430
[  168.981162]  ____sys_sendmsg+0x3bb/0x3f0
[  168.982155]  ___sys_sendmsg+0x88/0xd0
[  168.985036]  __sys_sendmsg+0x59/0xa0
[  168.985477]  do_syscall_64+0x79/0x150
[  168.987273]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[  168.987773] RIP: 0033:0x7f8f7950f917

(esw->fdb_table.legacy.vepa_fdb is null)

The bridge mode is only relevant when there are multiple functions per
port. Therefore, prevent setting and getting this setting when there are no
VFs.

Note that after this change, there are no settings to change on the PF
interface using `bridge link` when there are no VFs, so the interface no
longer appears in the `bridge link` output.

The Linux kernel CVE team has assigned CVE-2024-46857 to this issue.

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

	Issue introduced in 5.1 with commit 4b89251de024 and fixed in 6.1.111 with commit 52c4beb79e09
	Issue introduced in 5.1 with commit 4b89251de024 and fixed in 6.6.52 with commit 65feee671e37
	Issue introduced in 5.1 with commit 4b89251de024 and fixed in 6.10.11 with commit 505ae01f75f8
	Issue introduced in 5.1 with commit 4b89251de024 and fixed in 6.11 with commit b1d305abef46

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-2024-46857
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/esw/legacy.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/52c4beb79e095e0631b5cac46ed48a2aefe51985
	https://git.kernel.org/stable/c/65feee671e37f3b6eda0b6af28f204b5bcf7fa50
	https://git.kernel.org/stable/c/505ae01f75f839b54329164bbfecf24cc1361b31
	https://git.kernel.org/stable/c/b1d305abef4640af1b4f1b4774d513cd81b10cfc