[NETFILTER]: ipt_recent: avoid a possible NULL pointer deref in recent_seq_open()

If the call to seq_open() returns != 0 then the code calls 
kfree(st) but then on the very next line proceeds to 
dereference the pointer - not good.

Problem spotted by the Coverity checker.
Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/netfilter/ipt_recent.c

@@ -387,12 +387,17 @@ static int recent_seq_open(struct inode *inode, struct file *file)
 	st = kzalloc(sizeof(*st), GFP_KERNEL);
 	if (st == NULL)
 		return -ENOMEM;
+
 	ret = seq_open(file, &recent_seq_ops);
-	if (ret)
+	if (ret) {
 		kfree(st);
+		goto out;
+	}
+
 	st->table    = pde->data;
 	seq          = file->private_data;
 	seq->private = st;
+out:
 	return ret;
 }