[patch 10/20] : ulog: fix panic on SMP kernels

[Greg KH <gregkh@suse.de>]

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

------------------
From: Mark Huang <mlhuang@cs.princeton.edu>

[NETFILTER]: ulog: fix panic on SMP kernels

Fix kernel panic on various SMP machines. The culprit is a null
ub->skb in ulog_send(). If ulog_timer() has already been scheduled on
one CPU and is spinning on the lock, and ipt_ulog_packet() flushes the
queue on another CPU by calling ulog_send() right before it exits,
there will be no skbuff when ulog_timer() acquires the lock and calls
ulog_send(). Cancelling the timer in ulog_send() doesn't help because
it has already been scheduled and is running on the first CPU.

Similar problem exists in ebt_ulog.c and nfnetlink_log.c.

Signed-off-by: Mark Huang <mlhuang@cs.princeton.edu>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 net/bridge/netfilter/ebt_ulog.c |    3 +++
 net/ipv4/netfilter/ipt_ULOG.c   |    5 +++++
 net/netfilter/nfnetlink_log.c   |    3 +++
 3 files changed, 11 insertions(+)

--- linux-2.6.17.9.orig/net/bridge/netfilter/ebt_ulog.c
+++ linux-2.6.17.9/net/bridge/netfilter/ebt_ulog.c
@@ -75,6 +75,9 @@ static void ulog_send(unsigned int nlgro
 	if (timer_pending(&ub->timer))
 		del_timer(&ub->timer);
 
+	if (!ub->skb)
+		return;
+
 	/* last nlmsg needs NLMSG_DONE */
 	if (ub->qlen > 1)
 		ub->lastnlh->nlmsg_type = NLMSG_DONE;
--- linux-2.6.17.9.orig/net/ipv4/netfilter/ipt_ULOG.c
+++ linux-2.6.17.9/net/ipv4/netfilter/ipt_ULOG.c
@@ -116,6 +116,11 @@ static void ulog_send(unsigned int nlgro
 		del_timer(&ub->timer);
 	}
 
+	if (!ub->skb) {
+		DEBUGP("ipt_ULOG: ulog_send: nothing to send\n");
+		return;
+	}
+
 	/* last nlmsg needs NLMSG_DONE */
 	if (ub->qlen > 1)
 		ub->lastnlh->nlmsg_type = NLMSG_DONE;
--- linux-2.6.17.9.orig/net/netfilter/nfnetlink_log.c
+++ linux-2.6.17.9/net/netfilter/nfnetlink_log.c
@@ -366,6 +366,9 @@ __nfulnl_send(struct nfulnl_instance *in
 	if (timer_pending(&inst->timer))
 		del_timer(&inst->timer);
 
+	if (!inst->skb)
+		return 0;
+
 	if (inst->qlen > 1)
 		inst->lastnlh->nlmsg_type = NLMSG_DONE;
 

--
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