[PATCH] net: wireless: ath: ath9k: Fix a possible data race in ath_chanctx_set_next

[PATCH] net: wireless: ath: ath9k: Fix a possible data race in ath_chanctx_set_next

[Jia-Ju Bai]

The write operation to "sc->next_chan" is protected by
the lock on line 1287, but the read operation to
this data on line 1262 is not protected by the lock.
Thus, there may exist a data race for "sc->next_chan".

To fix this data race, the read operation to "sc->next_chan" 
should be also protected by the lock.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 drivers/net/wireless/ath/ath9k/channel.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath9k/channel.c b/drivers/net/wireless/ath/ath9k/channel.c
index 1b05b5d7a038..ed3cd5523481 100644
--- a/drivers/net/wireless/ath/ath9k/channel.c
+++ b/drivers/net/wireless/ath/ath9k/channel.c
@@ -1257,12 +1257,12 @@ void ath_chanctx_set_next(struct ath_softc *sc, bool force)
 			"Stopping current chanctx: %d\n",
 			sc->cur_chan->chandef.center_freq1);
 		sc->cur_chan->stopped = true;
-		spin_unlock_bh(&sc->chan_lock);
 
 		if (sc->next_chan == &sc->offchannel.chan) {
 			getrawmonotonic(&ts);
 			measure_time = true;
 		}
+		spin_unlock_bh(&sc->chan_lock);
 
 		ath9k_chanctx_stop_queues(sc, sc->cur_chan);
 		queues_stopped = true;
-- 
2.17.0

Re: [PATCH] net: wireless: ath: ath9k: Fix a possible data race in ath_chanctx_set_next

[Kalle Valo]

Jia-Ju Bai <baijiaju1990@gmail.com> writes:

> The write operation to "sc->next_chan" is protected by
> the lock on line 1287, but the read operation to
> this data on line 1262 is not protected by the lock.
> Thus, there may exist a data race for "sc->next_chan".
>
> To fix this data race, the read operation to "sc->next_chan" 
> should be also protected by the lock.
>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>

I need this reviewed by someone else before I'm willing to take it.

-- 
Kalle Valo

Re: [PATCH] net: wireless: ath: ath9k: Fix a possible data race in ath_chanctx_set_next

[Toke Høiland-Jørgensen]

Kalle Valo <kvalo@codeaurora.org> writes:

> Jia-Ju Bai <baijiaju1990@gmail.com> writes:
>
>> The write operation to "sc->next_chan" is protected by
>> the lock on line 1287, but the read operation to
>> this data on line 1262 is not protected by the lock.
>> Thus, there may exist a data race for "sc->next_chan".
>>
>> To fix this data race, the read operation to "sc->next_chan" 
>> should be also protected by the lock.
>>
>> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
>
> I need this reviewed by someone else before I'm willing to take it.

Only possible issue I can see is that it puts a call to
getrawmonotonic() under the spinlock. Not sure if that has any bad
implications...

-Toke