RE: [PATCH v0] ieee802154/adf7242: defer destroy_workqueue call

[Hennerich, Michael]

> -----Original Message-----
> From: Lin Ma <linma@xxxxxxxxxx>
> Sent: Montag, 8. August 2022 05:42
> To: Hennerich, Michael <Michael.Hennerich@xxxxxxxxxx>;
> alex.aring@xxxxxxxxx; stefan@xxxxxxxxxxxxxxxxxx; davem@xxxxxxxxxxxxx;
> edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx; linux-
> wpan@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Cc: Lin Ma <linma@xxxxxxxxxx>
> Subject: [PATCH v0] ieee802154/adf7242: defer destroy_workqueue call
> 
> 
> There is a possible race condition (use-after-free) like below
> 
>   (FREE)                     |  (USE)
>   adf7242_remove             |  adf7242_channel
>    cancel_delayed_work_sync  |
>     destroy_workqueue (1)    |   adf7242_cmd_rx
>                              |    mod_delayed_work (2)
>                              |
> 
> The root cause for this race is that the upper layer (ieee802154) is unaware of
> this detaching event and the function adf7242_channel can be called without
> any checks.
> 
> To fix this, we can add a flag write at the beginning of adf7242_remove and
> add flag check in adf7242_channel. Or we can just defer the destructive
> operation like other commit 3e0588c291d6 ("hamradio: defer
> ax25 kfree after unregister_netdev") which let the
> ieee802154_unregister_hw() to handle the synchronization. This patch takes
> the second option.
> 
> Fixes: 58e9683d1475 ("net: ieee802154: adf7242: Fix OCL calibration
> runs")
> Signed-off-by: Lin Ma <linma@xxxxxxxxxx>

Acked-by: Michael Hennerich <michael.hennerich@xxxxxxxxxx>

> ---
>  drivers/net/ieee802154/adf7242.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ieee802154/adf7242.c
> b/drivers/net/ieee802154/adf7242.c
> index 6afdf1622944..efcc45aef508 100644
> --- a/drivers/net/ieee802154/adf7242.c
> +++ b/drivers/net/ieee802154/adf7242.c
> @@ -1310,10 +1310,11 @@ static void adf7242_remove(struct spi_device
> *spi)
> 
>  	debugfs_remove_recursive(lp->debugfs_root);
> 
> +	ieee802154_unregister_hw(lp->hw);
> +
>  	cancel_delayed_work_sync(&lp->work);
>  	destroy_workqueue(lp->wqueue);
> -
> -	ieee802154_unregister_hw(lp->hw);
> +
>  	mutex_destroy(&lp->bmux);
>  	ieee802154_free_hw(lp->hw);
>  }
> --
> 2.36.1