netdev - [PATCH v2] mwifiex: don't call del_timer

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Date:   Fri, 21 Aug 2020 17:27:19 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     Ganapathi Bhat <ganapathi.bhat@....com>,
        Brian Norris <briannorris@...omium.org>
Cc:     amitkarwar@...il.com, andreyknvl@...gle.com, davem@...emloft.net,
        dvyukov@...gle.com, huxinming820@...il.com, kvalo@...eaurora.org,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        nishants@...vell.com, syzkaller-bugs@...glegroups.com,
        syzbot <syzbot+373e6719b49912399d21@...kaller.appspotmail.com>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        syzbot <syzbot+dc4127f950da51639216@...kaller.appspotmail.com>
Subject: [PATCH v2] mwifiex: don't call del_timer_sync() on uninitialized timer

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@...kaller.appspotmail.com>
Cc: Ganapathi Bhat <ganapathi.bhat@....com>
Cc: Brian Norris <briannorris@...omium.org>
Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
---
 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