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

[Tetsuo Handa]

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].
Since mwifiex_usb_prepare_tx_aggr_skb() is calling del_timer() if
is_hold_timer_set == true, use the same condition for del_timer_sync().

[1] https://syzkaller.appspot.com/bug?id=fdeef9cf7348be8b8ab5b847f2ed993aba8ea7b6

Reported-by: syzbot <syzbot+373e6719b49912399d21@xxxxxxxxxxxxxxxxxxxxxxxxx>
Cc: Ganapathi Bhat <gbhat@xxxxxxxxxxx>
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
A patch from Ganapathi Bhat ( https://patchwork.kernel.org/patch/10990275/ ) is stalling
at https://lore.kernel.org/linux-usb/MN2PR18MB2637D7C742BC235FE38367F0A09C0@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ .
syzbot by now got this report for 10000 times. Do we want to go with this simple patch?

 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 6f3cfde..04a1461 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.is_hold_timer_set)
+			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;
 	}
-- 
1.8.3.1