[NETFILTER]: xt_helper: use RCU

The ->helper pointer is protected by RCU, no need to take
nf_conntrack_lock. Also remove excessive debugging.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 23 deletions

diff --git a/net/netfilter/xt_helper.c b/net/netfilter/xt_helper.c
index d03acb032cc8..0a1f4c6bcdef 100644
--- a/net/netfilter/xt_helper.c
+++ b/net/netfilter/xt_helper.c
@@ -22,11 +22,6 @@ MODULE_DESCRIPTION("iptables helper match module");
 MODULE_ALIAS("ipt_helper");
 MODULE_ALIAS("ip6t_helper");
 
-#if 0
-#define DEBUGP printk
-#else
-#define DEBUGP(format, args...)
-#endif
 
 static bool
 match(const struct sk_buff *skb,
@@ -41,38 +36,28 @@ match(const struct sk_buff *skb,
         const struct xt_helper_info *info = matchinfo;
         const struct nf_conn *ct;
         const struct nf_conn_help *master_help;
+        const struct nf_conntrack_helper *helper;
         enum ip_conntrack_info ctinfo;
         bool ret = info->invert;
 
         ct = nf_ct_get(skb, &ctinfo);
-        if (!ct) {
-                DEBUGP("xt_helper: Eek! invalid conntrack?\n");
+        if (!ct || !ct->master)
                 return ret;
-        }
-
-        if (!ct->master) {
-                DEBUGP("xt_helper: conntrack %p has no master\n", ct);
-                return ret;
-        }
 
-        read_lock_bh(&nf_conntrack_lock);
         master_help = nfct_help(ct->master);
-        if (!master_help || !master_help->helper) {
-                DEBUGP("xt_helper: master ct %p has no helper\n",
-                        exp->expectant);
-                goto out_unlock;
-        }
+        if (!master_help)
+                return ret;
 
-        DEBUGP("master's name = %s , info->name = %s\n",
-                ct->master->helper->name, info->name);
+        /* rcu_read_lock()ed by nf_hook_slow */
+        helper = rcu_dereference(master_help->helper);
+        if (!helper)
+                return ret;
 
         if (info->name[0] == '\0')
                 ret = !ret;
         else
                 ret ^= !strncmp(master_help->helper->name, info->name,
                                 strlen(master_help->helper->name));
-out_unlock:
-        read_unlock_bh(&nf_conntrack_lock);
         return ret;
 }