[PATCH 2.4] netfilter ipt_helper locking fix

From: Harald Welte (laforge@netfilter.org)
Date: Fri Jul 25 2003 - 15:50:58 EST

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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