[NETFILTER]: nf_queue: Use RCU and mutex for queue handlers
Yasuyuki Kozakai [Sun, 8 Jul 2007 05:40:26 +0000 (22:40 -0700)]
Queue handlers are registered/unregistered in only process context.

Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/nf_queue.c

index f402894..823fbf4 100644 (file)
@@ -17,7 +17,7 @@
  */
 static struct nf_queue_handler *queue_handler[NPROTO];
 
-static DEFINE_RWLOCK(queue_handler_lock);
+static DEFINE_MUTEX(queue_handler_mutex);
 
 /* return EBUSY when somebody else is registered, return EEXIST if the
  * same handler is registered, return 0 in case of success. */
@@ -28,16 +28,16 @@ int nf_register_queue_handler(int pf, struct nf_queue_handler *qh)
        if (pf >= NPROTO)
                return -EINVAL;
 
-       write_lock_bh(&queue_handler_lock);
+       mutex_lock(&queue_handler_mutex);
        if (queue_handler[pf] == qh)
                ret = -EEXIST;
        else if (queue_handler[pf])
                ret = -EBUSY;
        else {
-               queue_handler[pf] = qh;
+               rcu_assign_pointer(queue_handler[pf], qh);
                ret = 0;
        }
-       write_unlock_bh(&queue_handler_lock);
+       mutex_unlock(&queue_handler_mutex);
 
        return ret;
 }
@@ -49,14 +49,16 @@ int nf_unregister_queue_handler(int pf, struct nf_queue_handler *qh)
        if (pf >= NPROTO)
                return -EINVAL;
 
-       write_lock_bh(&queue_handler_lock);
+       mutex_lock(&queue_handler_mutex);
        if (queue_handler[pf] != qh) {
-               write_unlock_bh(&queue_handler_lock);
+               mutex_unlock(&queue_handler_mutex);
                return -EINVAL;
        }
 
-       queue_handler[pf] = NULL;
-       write_unlock_bh(&queue_handler_lock);
+       rcu_assign_pointer(queue_handler[pf], NULL);
+       mutex_unlock(&queue_handler_mutex);
+
+       synchronize_rcu();
 
        return 0;
 }
@@ -66,12 +68,14 @@ void nf_unregister_queue_handlers(struct nf_queue_handler *qh)
 {
        int pf;
 
-       write_lock_bh(&queue_handler_lock);
+       mutex_lock(&queue_handler_mutex);
        for (pf = 0; pf < NPROTO; pf++)  {
                if (queue_handler[pf] == qh)
-                       queue_handler[pf] = NULL;
+                       rcu_assign_pointer(queue_handler[pf], NULL);
        }
-       write_unlock_bh(&queue_handler_lock);
+       mutex_unlock(&queue_handler_mutex);
+
+       synchronize_rcu();
 }
 EXPORT_SYMBOL_GPL(nf_unregister_queue_handlers);
 
@@ -94,18 +98,21 @@ static int __nf_queue(struct sk_buff *skb,
        struct net_device *physoutdev = NULL;
 #endif
        struct nf_afinfo *afinfo;
+       struct nf_queue_handler *qh;
 
        /* QUEUE == DROP if noone is waiting, to be safe. */
-       read_lock(&queue_handler_lock);
-       if (!queue_handler[pf]) {
-               read_unlock(&queue_handler_lock);
+       rcu_read_lock();
+
+       qh = rcu_dereference(queue_handler[pf]);
+       if (!qh) {
+               rcu_read_unlock();
                kfree_skb(skb);
                return 1;
        }
 
        afinfo = nf_get_afinfo(pf);
        if (!afinfo) {
-               read_unlock(&queue_handler_lock);
+               rcu_read_unlock();
                kfree_skb(skb);
                return 1;
        }
@@ -115,7 +122,7 @@ static int __nf_queue(struct sk_buff *skb,
                if (net_ratelimit())
                        printk(KERN_ERR "OOM queueing packet %p\n",
                               skb);
-               read_unlock(&queue_handler_lock);
+               rcu_read_unlock();
                kfree_skb(skb);
                return 1;
        }
@@ -125,7 +132,7 @@ static int __nf_queue(struct sk_buff *skb,
 
        /* If it's going away, ignore hook. */
        if (!try_module_get(info->elem->owner)) {
-               read_unlock(&queue_handler_lock);
+               rcu_read_unlock();
                kfree(info);
                return 0;
        }
@@ -143,10 +150,9 @@ static int __nf_queue(struct sk_buff *skb,
        }
 #endif
        afinfo->saveroute(skb, info);
-       status = queue_handler[pf]->outfn(skb, info, queuenum,
-                                         queue_handler[pf]->data);
+       status = qh->outfn(skb, info, queuenum, qh->data);
 
-       read_unlock(&queue_handler_lock);
+       rcu_read_unlock();
 
        if (status < 0) {
                /* James M doesn't say fuck enough. */
@@ -313,13 +319,13 @@ static int seq_show(struct seq_file *s, void *v)
        loff_t *pos = v;
        struct nf_queue_handler *qh;
 
-       read_lock_bh(&queue_handler_lock);
-       qh = queue_handler[*pos];
+       rcu_read_lock();
+       qh = rcu_dereference(queue_handler[*pos]);
        if (!qh)
                ret = seq_printf(s, "%2lld NONE\n", *pos);
        else
                ret = seq_printf(s, "%2lld %s\n", *pos, qh->name);
-       read_unlock_bh(&queue_handler_lock);
+       rcu_read_unlock();
 
        return ret;
 }