Messages in this thread | | | Date | Sat, 14 Jun 2008 10:50:51 +0800 | From | "Dave Young" <> | Subject | Re: [patch 16/47] bluetooth: fix locking bug in the rfcomm socket cleanup handling |
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On Sat, Jun 14, 2008 at 8:10 AM, Greg KH <gregkh@suse.de> wrote: > -stable review patch. If anyone has any objections, please let us know. > > ------------------ > From: Arjan van de Ven <arjan@linux.intel.com> > > [ Upstream commit: 7dccf1f4e1696c79bff064c3770867cc53cbc71c ]
Hi greg Please including following commit as well because it will cause another bug: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=537d59af73d894750cff14f90fe2b6d77fbab15b
> > in net/bluetooth/rfcomm/sock.c, rfcomm_sk_state_change() does the > following operation: > > if (parent && sock_flag(sk, SOCK_ZAPPED)) { > /* We have to drop DLC lock here, otherwise > * rfcomm_sock_destruct() will dead lock. */ > rfcomm_dlc_unlock(d); > rfcomm_sock_kill(sk); > rfcomm_dlc_lock(d); > } > } > > which is fine, since rfcomm_sock_kill() will call sk_free() which will call > rfcomm_sock_destruct() which takes the rfcomm_dlc_lock()... so far so good. > > HOWEVER, this assumes that the rfcomm_sk_state_change() function always gets > called with the rfcomm_dlc_lock() taken. This is the case for all but one > case, and in that case where we don't have the lock, we do a double unlock > followed by an attempt to take the lock, which due to underflow isn't > going anywhere fast. > > This patch fixes this by moving the stragling case inside the lock, like > the other usages of the same call are doing in this code. > > This was found with the help of the www.kerneloops.org project, where this > deadlock was observed 51 times at this point in time: > http://www.kerneloops.org/search.php?search=rfcomm_sock_destruct > > Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> > Acked-by: Marcel Holtmann <marcel@holtmann.org> > Signed-off-by: David S. Miller <davem@davemloft.net> > Signed-off-by: Chris Wright <chrisw@sous-sol.org> > --- > net/bluetooth/rfcomm/core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- a/net/bluetooth/rfcomm/core.c > +++ b/net/bluetooth/rfcomm/core.c > @@ -423,8 +423,8 @@ static int __rfcomm_dlc_close(struct rfc > > rfcomm_dlc_lock(d); > d->state = BT_CLOSED; > - rfcomm_dlc_unlock(d); > d->state_change(d, err); > + rfcomm_dlc_unlock(d); > > skb_queue_purge(&d->tx_queue); > rfcomm_dlc_unlink(d); > > -- > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
-- Regards dave
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