Message-ID: <2025040146-CVE-2025-21970-fbac@gregkh>
Date: Tue,  1 Apr 2025 16:45:55 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21970: net/mlx5: Bridge, fix the crash caused by LAG state check

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

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

net/mlx5: Bridge, fix the crash caused by LAG state check

When removing LAG device from bridge, NETDEV_CHANGEUPPER event is
triggered. Driver finds the lower devices (PFs) to flush all the
offloaded entries. And mlx5_lag_is_shared_fdb is checked, it returns
false if one of PF is unloaded. In such case,
mlx5_esw_bridge_lag_rep_get() and its caller return NULL, instead of
the alive PF, and the flush is skipped.

Besides, the bridge fdb entry's lastuse is updated in mlx5 bridge
event handler. But this SWITCHDEV_FDB_ADD_TO_BRIDGE event can be
ignored in this case because the upper interface for bond is deleted,
and the entry will never be aged because lastuse is never updated.

To make things worse, as the entry is alive, mlx5 bridge workqueue
keeps sending that event, which is then handled by kernel bridge
notifier. It causes the following crash when accessing the passed bond
netdev which is already destroyed.

To fix this issue, remove such checks. LAG state is already checked in
commit 15f8f168952f ("net/mlx5: Bridge, verify LAG state when adding
bond to bridge"), driver still need to skip offload if LAG becomes
invalid state after initialization.

 Oops: stack segment: 0000 [#1] SMP
 CPU: 3 UID: 0 PID: 23695 Comm: kworker/u40:3 Tainted: G           OE      6.11.0_mlnx #1
 Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 Workqueue: mlx5_bridge_wq mlx5_esw_bridge_update_work [mlx5_core]
 RIP: 0010:br_switchdev_event+0x2c/0x110 [bridge]
 Code: 44 00 00 48 8b 02 48 f7 00 00 02 00 00 74 69 41 54 55 53 48 83 ec 08 48 8b a8 08 01 00 00 48 85 ed 74 4a 48 83 fe 02 48 89 d3 <4c> 8b 65 00 74 23 76 49 48 83 fe 05 74 7e 48 83 fe 06 75 2f 0f b7
 RSP: 0018:ffffc900092cfda0 EFLAGS: 00010297
 RAX: ffff888123bfe000 RBX: ffffc900092cfe08 RCX: 00000000ffffffff
 RDX: ffffc900092cfe08 RSI: 0000000000000001 RDI: ffffffffa0c585f0
 RBP: 6669746f6e690a30 R08: 0000000000000000 R09: ffff888123ae92c8
 R10: 0000000000000000 R11: fefefefefefefeff R12: ffff888123ae9c60
 R13: 0000000000000001 R14: ffffc900092cfe08 R15: 0000000000000000
 FS:  0000000000000000(0000) GS:ffff88852c980000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00007f15914c8734 CR3: 0000000002830005 CR4: 0000000000770ef0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 PKRU: 55555554
 Call Trace:
  <TASK>
  ? __die_body+0x1a/0x60
  ? die+0x38/0x60
  ? do_trap+0x10b/0x120
  ? do_error_trap+0x64/0xa0
  ? exc_stack_segment+0x33/0x50
  ? asm_exc_stack_segment+0x22/0x30
  ? br_switchdev_event+0x2c/0x110 [bridge]
  ? sched_balance_newidle.isra.149+0x248/0x390
  notifier_call_chain+0x4b/0xa0
  atomic_notifier_call_chain+0x16/0x20
  mlx5_esw_bridge_update+0xec/0x170 [mlx5_core]
  mlx5_esw_bridge_update_work+0x19/0x40 [mlx5_core]
  process_scheduled_works+0x81/0x390
  worker_thread+0x106/0x250
  ? bh_worker+0x110/0x110
  kthread+0xb7/0xe0
  ? kthread_park+0x80/0x80
  ret_from_fork+0x2d/0x50
  ? kthread_park+0x80/0x80
  ret_from_fork_asm+0x11/0x20
  </TASK>

The Linux kernel CVE team has assigned CVE-2025-21970 to this issue.


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

	Issue introduced in 5.15 with commit ff9b7521468bc2909293c1cda66a245a49688f6f and fixed in 6.1.132 with commit 86ff45f5f61ae1d0d17f0f6d8797b052eacfd8f1
	Issue introduced in 5.15 with commit ff9b7521468bc2909293c1cda66a245a49688f6f and fixed in 6.6.84 with commit bd7e3a42800743a7748c83243e4cafc1b995d4c4
	Issue introduced in 5.15 with commit ff9b7521468bc2909293c1cda66a245a49688f6f and fixed in 6.12.20 with commit f7bf259a04271165ae667ad21cfc60c6413f25ca
	Issue introduced in 5.15 with commit ff9b7521468bc2909293c1cda66a245a49688f6f and fixed in 6.13.8 with commit 5dd8bf6ab1d6db40f5d09603759fa88caec19e7f
	Issue introduced in 5.15 with commit ff9b7521468bc2909293c1cda66a245a49688f6f and fixed in 6.14 with commit 4b8eeed4fb105770ce6dc84a2c6ef953c7b71cbb

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-2025-21970
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/bridge.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/86ff45f5f61ae1d0d17f0f6d8797b052eacfd8f1
	https://git.kernel.org/stable/c/bd7e3a42800743a7748c83243e4cafc1b995d4c4
	https://git.kernel.org/stable/c/f7bf259a04271165ae667ad21cfc60c6413f25ca
	https://git.kernel.org/stable/c/5dd8bf6ab1d6db40f5d09603759fa88caec19e7f
	https://git.kernel.org/stable/c/4b8eeed4fb105770ce6dc84a2c6ef953c7b71cbb

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