From: Mark Huang <mlhuang@cs.princeton.edu>
Date: Mon, 14 Aug 2006 01:57:54 +0000 (-0700)
Subject: [NETFILTER]: ulog: fix panic on SMP kernels
X-Git-Tag: v2.6.18-rc5~97
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=dcb7cd97f133f7cfbd181149a1e60215a869f895;p=linux-2.6

[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: David S. Miller <davem@davemloft.net>
---

diff --git a/net/bridge/netfilter/ebt_ulog.c b/net/bridge/netfilter/ebt_ulog.c
index 02693a230d..9f950db3b7 100644
--- a/net/bridge/netfilter/ebt_ulog.c
+++ b/net/bridge/netfilter/ebt_ulog.c
@@ -74,6 +74,9 @@ static void ulog_send(unsigned int nlgroup)
 	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;
diff --git a/net/ipv4/netfilter/ipt_ULOG.c b/net/ipv4/netfilter/ipt_ULOG.c
index d7dd7fe705..d46fd677fa 100644
--- a/net/ipv4/netfilter/ipt_ULOG.c
+++ b/net/ipv4/netfilter/ipt_ULOG.c
@@ -115,6 +115,11 @@ static void ulog_send(unsigned int nlgroupnum)
 		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;
diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index 61cdda4e5d..b59d3b2bde 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -366,6 +366,9 @@ __nfulnl_send(struct nfulnl_instance *inst)
 	if (timer_pending(&inst->timer))
 		del_timer(&inst->timer);
 
+	if (!inst->skb)
+		return 0;
+
 	if (inst->qlen > 1)
 		inst->lastnlh->nlmsg_type = NLMSG_DONE;