Re: [PATCH v2] mwifiex: don't call del_timer_sync() on uninitialized timer

[Brian Norris]

On Fri, Aug 21, 2020 at 1:28 AM Tetsuo Handa
<penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote:
>
> syzbot is reporting that del_timer_sync() is called from
> mwifiex_usb_cleanup_tx_aggr() from mwifiex_unregister_dev() without
> checking timer_setup() from mwifiex_usb_tx_init() was called [1].
>
> Ganapathi Bhat proposed a possibly cleaner fix, but it seems that
> that fix was forgotten [2].
>
> "grep -FrB1 'del_timer' drivers/ | grep -FA1 '.function)'" says that
> currently there are 28 locations which call del_timer[_sync]() only if
> that timer's function field was initialized (because timer_setup() sets
> that timer's function field). Therefore, let's use same approach here.
>
> [1] https://syzkaller.appspot.com/bug?id=26525f643f454dd7be0078423e3cdb0d57744959
> [2] https://lkml.kernel.org/r/CA+ASDXMHt2gq9Hy+iP_BYkWXsSreWdp3_bAfMkNcuqJ3K+-jbQ@xxxxxxxxxxxxxx
>
> Reported-by: syzbot <syzbot+dc4127f950da51639216@xxxxxxxxxxxxxxxxxxxxxxxxx>
> Cc: Ganapathi Bhat <ganapathi.bhat@xxxxxxx>
> Cc: Brian Norris <briannorris@xxxxxxxxxxxx>
> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>

This seems good to me:

Reviewed-by: Brian Norris <briannorris@xxxxxxxxxxxx>

> ---
>  drivers/net/wireless/marvell/mwifiex/usb.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/marvell/mwifiex/usb.c b/drivers/net/wireless/marvell/mwifiex/usb.c
> index 6f3cfde4654c..426e39d4ccf0 100644
> --- a/drivers/net/wireless/marvell/mwifiex/usb.c
> +++ b/drivers/net/wireless/marvell/mwifiex/usb.c
> @@ -1353,7 +1353,8 @@ static void mwifiex_usb_cleanup_tx_aggr(struct mwifiex_adapter *adapter)
>                                 skb_dequeue(&port->tx_aggr.aggr_list)))
>                                 mwifiex_write_data_complete(adapter, skb_tmp,
>                                                             0, -1);
> -               del_timer_sync(&port->tx_aggr.timer_cnxt.hold_timer);
> +               if (port->tx_aggr.timer_cnxt.hold_timer.function)
> +                       del_timer_sync(&port->tx_aggr.timer_cnxt.hold_timer);
>                 port->tx_aggr.timer_cnxt.is_hold_timer_set = false;
>                 port->tx_aggr.timer_cnxt.hold_tmo_msecs = 0;
>         }
> --
> 2.18.4
>