linux-kernel - Re: [PATCH 2.6.20 13/14] nfnetlink

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Date:	Wed, 14 Feb 2007 12:38:41 +0100
From:	Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:	netfilter-devel@...ts.netfilter.org
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.20 13/14] nfnetlink_log: fix reference counting

On Tue, Feb 13, 2007 at 01:58:34PM +0100, Patrick McHardy wrote:
> Micha³ Miros³aw wrote:
> > Fix reference counting (memory leak) problem in __nfulnl_send() and callers
> > related to packet queueing.
> > 
> > Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
> > 
> > --- linux-2.6.20/net/netfilter/nfnetlink_log.c.11	2007-02-12 17:35:50.000000000 +0100
> > +++ linux-2.6.20/net/netfilter/nfnetlink_log.c	2007-02-12 17:58:01.000000000 +0100
> > @@ -223,6 +223,11 @@ _instance_destroy2(struct nfulnl_instanc
> >  
> >  	spin_lock_bh(&inst->lock);
> >  	if (inst->skb) {
> > +		/* timer "holds" one reference (we have one more) */
> > +		if (timer_pending(&inst->timer)) {
> > +			del_timer(&inst->timer);
> > +			instance_put(inst);
> This should be done outside of the locked section and using
> del_timer_sync to make sure the timer is not already active
> and waiting for the lock.

I found another solution, as this won't work (I explained the case in my
reply to your comment on 07/10). I noticed that we should just check
what del_timer() returns instead of timer_pending().

Heres the patch:

Fix reference counting (memory leak) problem in __nfulnl_send() and callers
related to packet queueing.

Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>

--- linux-2.6.20/net/netfilter/nfnetlink_log.c.11	2007-02-12 17:35:50.000000000 +0100
+++ linux-2.6.20/net/netfilter/nfnetlink_log.c.12	2007-02-14 12:27:09.000000000 +0100
@@ -223,6 +223,9 @@ _instance_destroy2(struct nfulnl_instanc
 
 	spin_lock_bh(&inst->lock);
 	if (inst->skb) {
+		/* timer "holds" one reference (we have one more) */
+		if (del_timer(&inst->timer))
+			instance_put(inst);
 		if (inst->qlen)
 			__nfulnl_send(inst);
 		if (inst->skb) {
@@ -370,9 +373,6 @@ __nfulnl_send(struct nfulnl_instance *in
 {
 	int status;
 
-	if (timer_pending(&inst->timer))
-		del_timer(&inst->timer);
-
 	if (!inst->skb)
 		return 0;
 
@@ -683,6 +683,9 @@ nfulnl_log_packet(unsigned int pf,
 		 * enough room in the skb left. flush to userspace. */
 		UDEBUG("flushing old skb\n");
 
+		/* timer "holds" one reference (we have another one) */
+		if (del_timer(&inst->timer))
+			instance_put(inst);
 		__nfulnl_send(inst);
 	}
 
-
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