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

From: Brian Norris <briannorris@chromium.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Ganapathi Bhat <ganapathi.bhat@nxp.com>,
	amit karwar <amitkarwar@gmail.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	"David S. Miller" <davem@davemloft.net>,
	Dmitry Vyukov <dvyukov@google.com>,
	Xinming Hu <huxinming820@gmail.com>,
	Kalle Valo <kvalo@codeaurora.org>,
	Linux Kernel <linux-kernel@vger.kernel.org>,
	Linux USB Mailing List <linux-usb@vger.kernel.org>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	"<netdev@vger.kernel.org>" <netdev@vger.kernel.org>,
	Nishant Sarmukadam <nishants@marvell.com>,
	syzkaller-bugs@googlegroups.com,
	syzbot <syzbot+373e6719b49912399d21@syzkaller.appspotmail.com>,
	syzbot <syzbot+dc4127f950da51639216@syzkaller.appspotmail.com>
Subject: Re: [PATCH v2] mwifiex: don't call del_timer_sync() on uninitialized timer
Date: Mon, 24 Aug 2020 11:52:53 -0700	[thread overview]
Message-ID: <CA+ASDXOHDU+SWmr+7aOUtbuzC22T-UWhZXJ5UXtcsev5ZTbqMw@mail.gmail.com> (raw)
In-Reply-To: <20200821082720.7716-1-penguin-kernel@I-love.SAKURA.ne.jp>

On Fri, Aug 21, 2020 at 1:28 AM Tetsuo Handa
<penguin-kernel@i-love.sakura.ne.jp> 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@mail.gmail.com
>
> Reported-by: syzbot <syzbot+dc4127f950da51639216@syzkaller.appspotmail.com>
> Cc: Ganapathi Bhat <ganapathi.bhat@nxp.com>
> Cc: Brian Norris <briannorris@chromium.org>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

This seems good to me:

Reviewed-by: Brian Norris <briannorris@chromium.org>

> ---
>  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
>