CVE-2025-21970

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>