l2tp: put tunnel socket release on a workqueue

To allow l2tp_tunnel_delete to be called from an atomic context, place the
tunnel socket release calls on a workqueue for asynchronous execution.

Tunnel memory is eventually freed in the tunnel socket destructor.

Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 06389d5..73988c0 100644 (file)
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -101,6 +101,7 @@ struct l2tp_skb_cb {
 
 static atomic_t l2tp_tunnel_count;
 static atomic_t l2tp_session_count;
+static struct workqueue_struct *l2tp_wq;
 
 /* per-net private data for this module */
 static unsigned int l2tp_net_id;
@@ -122,7 +123,6 @@ static inline struct l2tp_net *l2tp_pernet(struct net *net)
        return net_generic(net, l2tp_net_id);
 }
 
-
 /* Tunnel reference counts. Incremented per session that is added to
  * the tunnel.
  */
@@ -1277,6 +1277,7 @@ EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
 static void l2tp_tunnel_destruct(struct sock *sk)
 {
        struct l2tp_tunnel *tunnel;
+       struct l2tp_net *pn;
 
        tunnel = sk->sk_user_data;
        if (tunnel == NULL)
@@ -1284,9 +1285,8 @@ static void l2tp_tunnel_destruct(struct sock *sk)
 
        l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: closing...\n", tunnel->name);
 
-       /* Close all sessions */
-       l2tp_tunnel_closeall(tunnel);
 
+       /* Disable udp encapsulation */
        switch (tunnel->encap) {
        case L2TP_ENCAPTYPE_UDP:
                /* No longer an encapsulation socket. See net/ipv4/udp.c */
@@ -1298,17 +1298,23 @@ static void l2tp_tunnel_destruct(struct sock *sk)
        }
 
        /* Remove hooks into tunnel socket */
-       tunnel->sock = NULL;
        sk->sk_destruct = tunnel->old_sk_destruct;
        sk->sk_user_data = NULL;
+       tunnel->sock = NULL;
 
-       /* Call the original destructor */
-       if (sk->sk_destruct)
-               (*sk->sk_destruct)(sk);
+       /* Remove the tunnel struct from the tunnel list */
+       pn = l2tp_pernet(tunnel->l2tp_net);
+       spin_lock_bh(&pn->l2tp_tunnel_list_lock);
+       list_del_rcu(&tunnel->list);
+       spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
+       atomic_dec(&l2tp_tunnel_count);
 
-       /* We're finished with the socket */
+       l2tp_tunnel_closeall(tunnel);
        l2tp_tunnel_dec_refcount(tunnel);
 
+       /* Call the original destructor */
+       if (sk->sk_destruct)
+               (*sk->sk_destruct)(sk);
 end:
        return;
 }
@@ -1382,20 +1388,41 @@ again:
  */
 static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
 {
-       struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
-
        BUG_ON(atomic_read(&tunnel->ref_count) != 0);
        BUG_ON(tunnel->sock != NULL);
-
        l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: free...\n", tunnel->name);
-
-       /* Remove from tunnel list */
-       spin_lock_bh(&pn->l2tp_tunnel_list_lock);
-       list_del_rcu(&tunnel->list);
        kfree_rcu(tunnel, rcu);
-       spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
+}
 
-       atomic_dec(&l2tp_tunnel_count);
+/* Workqueue tunnel deletion function */
+static void l2tp_tunnel_del_work(struct work_struct *work)
+{
+       struct l2tp_tunnel *tunnel = NULL;
+       struct socket *sock = NULL;
+       struct sock *sk = NULL;
+
+       tunnel = container_of(work, struct l2tp_tunnel, del_work);
+       sk = l2tp_tunnel_sock_lookup(tunnel);
+       if (!sk)
+               return;
+
+       sock = sk->sk_socket;
+       BUG_ON(!sock);
+
+       /* Force the tunnel socket to close. This will eventually
+        * cause the tunnel to be deleted via the normal socket close
+        * mechanisms when userspace closes the tunnel socket.
+        */
+       inet_shutdown(sock, 2);
+
+       /* If the tunnel's socket was created by the kernel,
+        * close the socket here since the socket was not
+        * created by userspace.
+        */
+       if (sock->file == NULL)
+               inet_release(sock);
+
+       l2tp_tunnel_sock_put(sk);
 }
 
 /* Create a socket for the tunnel, if one isn't set up by
@@ -1657,6 +1684,9 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
 
        sk->sk_allocation = GFP_ATOMIC;
 
+       /* Init delete workqueue struct */
+       INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work);
+
        /* Add tunnel to our list */
        INIT_LIST_HEAD(&tunnel->list);
        atomic_inc(&l2tp_tunnel_count);
@@ -1688,33 +1718,7 @@ EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
  */
 int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
 {
-       int err = -EBADF;
-       struct socket *sock = NULL;
-       struct sock *sk = NULL;
-
-       sk = l2tp_tunnel_sock_lookup(tunnel);
-       if (!sk)
-               goto out;
-
-       sock = sk->sk_socket;
-       BUG_ON(!sock);
-
-       /* Force the tunnel socket to close. This will eventually
-        * cause the tunnel to be deleted via the normal socket close
-        * mechanisms when userspace closes the tunnel socket.
-        */
-       err = inet_shutdown(sock, 2);
-
-       /* If the tunnel's socket was created by the kernel,
-        * close the socket here since the socket was not
-        * created by userspace.
-        */
-       if (sock->file == NULL)
-               err = inet_release(sock);
-
-       l2tp_tunnel_sock_put(sk);
-out:
-       return err;
+       return (false == queue_work(l2tp_wq, &tunnel->del_work));
 }
 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
 
@@ -1912,6 +1916,13 @@ static int __init l2tp_init(void)
        if (rc)
                goto out;
 
+       l2tp_wq = alloc_workqueue("l2tp", WQ_NON_REENTRANT | WQ_UNBOUND, 0);
+       if (!l2tp_wq) {
+               pr_err("alloc_workqueue failed\n");
+               rc = -ENOMEM;
+               goto out;
+       }
+
        pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION);
 
 out:
@@ -1921,6 +1932,10 @@ out:
 static void __exit l2tp_exit(void)
 {
        unregister_pernet_device(&l2tp_net_ops);
+       if (l2tp_wq) {
+               destroy_workqueue(l2tp_wq);
+               l2tp_wq = NULL;
+       }
 }
 
 module_init(l2tp_init);

diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index e62204c..8eb8f1d 100644 (file)
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -191,6 +191,8 @@ struct l2tp_tunnel {
        int                     fd;             /* Parent fd, if tunnel socket
                                                 * was created by userspace */
 
+       struct work_struct      del_work;
+
        uint8_t                 priv[0];        /* private data */
 };