Re: [PATCH net v1] mac802154: drain mac_wq before unregistering interfaces

[Miquel Raynal]

On 28/08/2026 at 18:19:05 +08, Xuanqiang Luo <xuanqiang.luo@xxxxxxxxx> wrote:

> From: Xuanqiang Luo <luoxuanqiang@xxxxxxxxxx>
>
> ieee802154_unregister_hw() unregisters the wpan netdevs before
> destroying mac_wq. The RX path stores the receiving sub-interface
> (sdata) in the queued MAC command descriptor without taking a
> reference to the netdev.
>
> If mac802154_rx_mac_cmd_worker() runs after the netdev has been freed,
> it dereferences the stale pointer and triggers a KASAN
> slab-use-after-free:
>
>   BUG: KASAN: slab-use-after-free in mac802154_rx_mac_cmd_worker+0xc0/0x498 [mac802154]
>   Read of size 8 at addr ffff0000c6db0ba8 by task kworker/u16:3/61
>   ...
>   Call trace:
>    show_stack+0x20/0x38 (C)
>    dump_stack_lvl+0x78/0x90
>    print_address_description.constprop.0+0x88/0x398
>    print_report+0xa8/0x278
>    kasan_report+0xa8/0xf8
>    __asan_load8+0x9c/0xc0
>    mac802154_rx_mac_cmd_worker+0xc0/0x498 [mac802154]
>    process_one_work+0x334/0x8b8
>   ...
>   Allocated by task 630:
>    kasan_save_stack+0x2c/0x58
>    kasan_save_track+0x20/0x40
>    kasan_save_alloc_info+0x40/0x58
>    __kasan_kmalloc+0xa0/0xb8
>    __kvmalloc_node_noprof+0x1e8/0x588
>    alloc_netdev_mqs+0x74/0x7f0
>    ieee802154_if_add+0xac/0x630 [mac802154]
>    ieee802154_register_hw+0x31c/0x3d0 [mac802154]
>    fakelb_add_one+0x250/0x318 [fakelb]
>   ...
>   Freed by task 652:
>    kasan_save_stack+0x2c/0x58
>    kasan_save_track+0x20/0x40
>    kasan_save_free_info+0x4c/0x78
>    __kasan_slab_free+0x60/0x90
>    kfree+0x194/0x478
>    kvfree+0x44/0x60
>    netdev_release+0x4c/0x68
>    device_release+0xac/0x130
>    kobject_cleanup+0x84/0x248
>    kobject_put+0x98/0xf8
>    netdev_run_todo+0x3a0/0x5e0
>    rtnl_unlock+0x18/0x30
>    ieee802154_unregister_hw+0x48/0x90 [mac802154]
>    fakelb_remove+0xe8/0x148 [fakelb]
>
> After killing local->tasklet, drain mac_wq before calling
> ieee802154_remove_interfaces() so pending work completes before the
> interfaces are unregistered. Do this without holding rtnl because scan
> and beacon workers acquire it themselves.
>
> Fixes: d021d218f6d9 ("mac802154: Handle received BEACON_REQ")
> Signed-off-by: Xuanqiang Luo <luoxuanqiang@xxxxxxxxxx>

Missing Cc: stable.

Reviewed-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>

Thanks,
Miquèl