CVE-2025-21970 Information

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 ( et/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: ? __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

Reference

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