b43: Workaround circular locking in hw-tkip key update callback

The TKIP key update callback is called from the RX path, where the driver
mutex is already locked. This results in a circular locking bug.
Avoid this by removing the lock.

Johannes noted that there is a separate bug: The callback still breaks on SDIO
hardware, because SDIO hardware access needs to sleep, but we are not allowed
to sleep in the callback due to mac80211's RCU locking.

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Tested-by: Larry Finger <Larry.Finger@lwfinger.net>
Reported-by: kecsa@kutfo.hit.bme.hu
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: stable <stable@kernel.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/drivers/net/wireless/b43/main.c b/drivers/net/wireless/b43/main.c
index 6d7cf3c..66220cd 100644 (file)
--- a/drivers/net/wireless/b43/main.c
+++ b/drivers/net/wireless/b43/main.c
@@ -856,22 +856,19 @@ static void b43_op_update_tkip_key(struct ieee80211_hw *hw,
        if (B43_WARN_ON(!modparam_hwtkip))
                return;
 
-       mutex_lock(&wl->mutex);
-
+       /* This is only called from the RX path through mac80211, where
+        * our mutex is already locked. */
+       B43_WARN_ON(!mutex_is_locked(&wl->mutex));
        dev = wl->current_dev;
-       if (!dev || b43_status(dev) < B43_STAT_INITIALIZED)
-               goto out_unlock;
+       B43_WARN_ON(!dev || b43_status(dev) < B43_STAT_INITIALIZED);
 
        keymac_write(dev, index, NULL); /* First zero out mac to avoid race */
 
        rx_tkip_phase1_write(dev, index, iv32, phase1key);
        /* only pairwise TKIP keys are supported right now */
        if (WARN_ON(!sta))
-               goto out_unlock;
+               return;
        keymac_write(dev, index, sta->addr);
-
-out_unlock:
-       mutex_unlock(&wl->mutex);
 }
 
 static void do_key_write(struct b43_wldev *dev,