[PATCH 2.4] netfilter ipt_helper locking fix

[PATCH 2.4] netfilter ipt_helper locking fix

[Harald Welte]

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Hi Dave!

This is the 4th of a set of bugfixes (all tested against 2.4.22-pre7).
You might need to apply them incrementally (didn't test it in a
different order).  You will receive 2.6 merges of those patches soon.

Author: Patrick McHardy <kaber@trash.net>

Fix locking of ipt_helper.

Please apply,

diff -Nru a/net/ipv4/netfilter/ipt_helper.c b/net/ipv4/netfilter/ipt_helper.c
--- a/net/ipv4/netfilter/ipt_helper.c	Sat Jul 12 04:57:37 2003
+++ b/net/ipv4/netfilter/ipt_helper.c	Sat Jul 12 04:57:37 2003
@@ -10,6 +10,7 @@
 #include <linux/module.h>
 #include <linux/skbuff.h>
 #include <linux/netfilter_ipv4/ip_conntrack.h>
+#include <linux/netfilter_ipv4/ip_conntrack_core.h>
 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
 #include <linux/netfilter_ipv4/ip_tables.h>
 #include <linux/netfilter_ipv4/ipt_helper.h>
@@ -36,6 +37,7 @@
 	struct ip_conntrack_expect *exp;
 	struct ip_conntrack *ct;
 	enum ip_conntrack_info ctinfo;
+	int ret = 0;
 	
 	ct = ip_conntrack_get((struct sk_buff *)skb, &ctinfo);
 	if (!ct) {
@@ -49,23 +51,27 @@
 	}
 
 	exp = ct->master;
+	READ_LOCK(&ip_conntrack_lock);
 	if (!exp->expectant) {
 		DEBUGP("ipt_helper: expectation %p without expectant !?!\n", 
 			exp);
-		return 0;
+		goto out_unlock;
 	}
 
 	if (!exp->expectant->helper) {
 		DEBUGP("ipt_helper: master ct %p has no helper\n", 
 			exp->expectant);
-		return 0;
+		goto out_unlock;
 	}
 
 	DEBUGP("master's name = %s , info->name = %s\n", 
 		exp->expectant->helper->name, info->name);
 
-	return !strncmp(exp->expectant->helper->name, info->name, 
-			strlen(exp->expectant->helper->name)) ^ info->invert;
+	ret = !strncmp(exp->expectant->helper->name, info->name, 
+	               strlen(exp->expectant->helper->name)) ^ info->invert;
+out_unlock:
+	READ_UNLOCK(&ip_conntrack_lock);
+	return ret;
 }
 
 static int check(const char *tablename,
-- 
- Harald Welte <laforge@netfilter.org>             http://www.netfilter.org/
============================================================================
  "Fragmentation is like classful addressing -- an interesting early
   architectural error that shows how much experimentation was going
   on while IP was being designed."                    -- Paul Vixie

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