[PATCH]: fix ipt_helper locking

[PATCH]: fix ipt_helper locking

[Patrick McHardy]

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Hi Martin,
this patch fixes locking of ipt_helper. We need to hold ip_conntrack_lock
when dereferencing exp->expectant.

Best regards,
Patrick


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# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
#	           ChangeSet	1.1213  -> 1.1214 
#	net/ipv4/netfilter/ipt_helper.c	1.1     -> 1.2    
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 03/07/12	kaber@trash.net		1.1214
# [NETFILTER]: Fix ipt_helper locking (must hold ip_conntrack_lock when dereferencing exp->expectant).
# --------------------------------------------
#
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,

Re: [PATCH]: fix ipt_helper locking

[Harald Welte]

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On Sat, Jul 12, 2003 at 12:44:30PM +0200, Patrick McHardy wrote:
> Hi Martin,
> this patch fixes locking of ipt_helper. We need to hold ip_conntrack_lock
> when dereferencing exp->expectant.

Thanks, I'll apply it to CVS once I return to some IP connectivity (I'm
travelling right now)

> Best regards,
> Patrick

-- 
- 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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