linux-kernel - [112/116] b43: Workaround circular locking in hw-tkip key update callback

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Message-Id: <20100330225713.553002971@linux.site>
Date:	Tue, 30 Mar 2010 15:56:30 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org,
	Greg Kroah-Hartman <gregkh@...e.de>
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Michael Buesch <mb@...sch.de>,
	Johannes Berg <johannes@...solutions.net>,
	"John W. Linville" <linville@...driver.com>
Subject: [112/116] b43: Workaround circular locking in hw-tkip key update callback

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Michael Buesch <mb@...sch.de>

commit 96869a39399269a776a94812e9fff3d38b47d838 upstream

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@...sch.de>
Tested-by: Larry Finger <Larry.Finger@...inger.net>
Reported-by: kecsa@...fo.hit.bme.hu
Cc: Johannes Berg <johannes@...solutions.net>
Signed-off-by: John W. Linville <linville@...driver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/net/wireless/b43/main.c |   11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

--- a/drivers/net/wireless/b43/main.c
+++ b/drivers/net/wireless/b43/main.c
@@ -852,19 +852,16 @@ static void b43_op_update_tkip_key(struc
 	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);
 	keymac_write(dev, index, addr);
-
-out_unlock:
-	mutex_unlock(&wl->mutex);
 }
 
 static void do_key_write(struct b43_wldev *dev,


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