[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>

diff --git a/net/netfilter/xt_helper.c b/net/netfilter/xt_helper.c
index d03acb0..0a1f4c6 100644 (file)
--- 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;
 }