linux-cve-announce - CVE-2025-38019: mlxsw: spectrum_router: Fix use-after-free when deleting GRE net devices

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Message-ID: <2025061845-CVE-2025-38019-efab@gregkh>
Date: Wed, 18 Jun 2025 11:28:53 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38019: mlxsw: spectrum_router: Fix use-after-free when deleting GRE net devices

From: Greg Kroah-Hartman <gregkh@...nel.org>

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

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

mlxsw: spectrum_router: Fix use-after-free when deleting GRE net devices

The driver only offloads neighbors that are constructed on top of net
devices registered by it or their uppers (which are all Ethernet). The
device supports GRE encapsulation and decapsulation of forwarded
traffic, but the driver will not offload dummy neighbors constructed on
top of GRE net devices as they are not uppers of its net devices:

 # ip link add name gre1 up type gre tos inherit local 192.0.2.1 remote 198.51.100.1
 # ip neigh add 0.0.0.0 lladdr 0.0.0.0 nud noarp dev gre1
 $ ip neigh show dev gre1 nud noarp
 0.0.0.0 lladdr 0.0.0.0 NOARP

(Note that the neighbor is not marked with 'offload')

When the driver is reloaded and the existing configuration is replayed,
the driver does not perform the same check regarding existing neighbors
and offloads the previously added one:

 # devlink dev reload pci/0000:01:00.0
 $ ip neigh show dev gre1 nud noarp
 0.0.0.0 lladdr 0.0.0.0 offload NOARP

If the neighbor is later deleted, the driver will ignore the
notification (given the GRE net device is not its upper) and will
therefore keep referencing freed memory, resulting in a use-after-free
[1] when the net device is deleted:

 # ip neigh del 0.0.0.0 lladdr 0.0.0.0 dev gre1
 # ip link del dev gre1

Fix by skipping neighbor replay if the net device for which the replay
is performed is not our upper.

[1]
BUG: KASAN: slab-use-after-free in mlxsw_sp_neigh_entry_update+0x1ea/0x200
Read of size 8 at addr ffff888155b0e420 by task ip/2282
[...]
Call Trace:
 <TASK>
 dump_stack_lvl+0x6f/0xa0
 print_address_description.constprop.0+0x6f/0x350
 print_report+0x108/0x205
 kasan_report+0xdf/0x110
 mlxsw_sp_neigh_entry_update+0x1ea/0x200
 mlxsw_sp_router_rif_gone_sync+0x2a8/0x440
 mlxsw_sp_rif_destroy+0x1e9/0x750
 mlxsw_sp_netdevice_ipip_ol_event+0x3c9/0xdc0
 mlxsw_sp_router_netdevice_event+0x3ac/0x15e0
 notifier_call_chain+0xca/0x150
 call_netdevice_notifiers_info+0x7f/0x100
 unregister_netdevice_many_notify+0xc8c/0x1d90
 rtnl_dellink+0x34e/0xa50
 rtnetlink_rcv_msg+0x6fb/0xb70
 netlink_rcv_skb+0x131/0x360
 netlink_unicast+0x426/0x710
 netlink_sendmsg+0x75a/0xc20
 __sock_sendmsg+0xc1/0x150
 ____sys_sendmsg+0x5aa/0x7b0
 ___sys_sendmsg+0xfc/0x180
 __sys_sendmsg+0x121/0x1b0
 do_syscall_64+0xbb/0x1d0
 entry_SYSCALL_64_after_hwframe+0x4b/0x53

The Linux kernel CVE team has assigned CVE-2025-38019 to this issue.


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

	Issue introduced in 6.6 with commit 8fdb09a7674c61c4f0e5faf0d63b3ce500a341b0 and fixed in 6.6.92 with commit f1ecccb5cdda39bca8cd17bb0b6cf61361e33578
	Issue introduced in 6.6 with commit 8fdb09a7674c61c4f0e5faf0d63b3ce500a341b0 and fixed in 6.12.30 with commit abc43c1ffdbc801b0b04ac845bfaf1d42b8f68f7
	Issue introduced in 6.6 with commit 8fdb09a7674c61c4f0e5faf0d63b3ce500a341b0 and fixed in 6.14.8 with commit 9ab7945f3a61ed23da412e30f1e56414c05c4f06
	Issue introduced in 6.6 with commit 8fdb09a7674c61c4f0e5faf0d63b3ce500a341b0 and fixed in 6.15 with commit 92ec4855034b2c4d13f117558dc73d20581fa9ff

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-2025-38019
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_router.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/f1ecccb5cdda39bca8cd17bb0b6cf61361e33578
	https://git.kernel.org/stable/c/abc43c1ffdbc801b0b04ac845bfaf1d42b8f68f7
	https://git.kernel.org/stable/c/9ab7945f3a61ed23da412e30f1e56414c05c4f06
	https://git.kernel.org/stable/c/92ec4855034b2c4d13f117558dc73d20581fa9ff