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>

2 files changed, 61 insertions, 44 deletions

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 06389d5ff120..73988c070561 100644
--- 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 e62204cad4fe..8eb8f1d47f3a 100644
--- 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 */
 };