rxrpc: Fix missing active use pinning of rxrpc_local object

[ Upstream commit 04d36d748fac349b068ef621611f454010054c58 ]

The introduction of a split between the reference count on rxrpc_local
objects and the usage count didn't quite go far enough.  A number of kernel
work items need to make use of the socket to perform transmission.  These
also need to get an active count on the local object to prevent the socket
from being closed.

Fix this by getting the active count in those places.

Also split out the raw active count get/put functions as these places tend
to hold refs on the rxrpc_local object already, so getting and putting an
extra object ref is just a waste of time.

The problem can lead to symptoms like:

    BUG: kernel NULL pointer dereference, address: 0000000000000018
    ..
    CPU: 2 PID: 818 Comm: kworker/u9:0 Not tainted 5.5.0-fscache+ #51
    ...
    RIP: 0010:selinux_socket_sendmsg+0x5/0x13
    ...
    Call Trace:
     security_socket_sendmsg+0x2c/0x3e
     sock_sendmsg+0x1a/0x46
     rxrpc_send_keepalive+0x131/0x1ae
     rxrpc_peer_keepalive_worker+0x219/0x34b
     process_one_work+0x18e/0x271
     worker_thread+0x1a3/0x247
     kthread+0xe6/0xeb
     ret_from_fork+0x1f/0x30

Fixes: 730c5fd42c1e ("rxrpc: Fix local endpoint refcounting")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/rxrpc/af_rxrpc.c b/net/rxrpc/af_rxrpc.c
index a74edb10cbfc6ff72f9cb78f788f65f0c1134301..57f835d2442ec9b2b7a9cc9e8223f3330e517e49 100644 (file)
--- a/net/rxrpc/af_rxrpc.c
+++ b/net/rxrpc/af_rxrpc.c
@@ -196,6 +196,7 @@ static int rxrpc_bind(struct socket *sock, struct sockaddr *saddr, int len)
 service_in_use:
        write_unlock(&local->services_lock);
        rxrpc_unuse_local(local);
+       rxrpc_put_local(local);
        ret = -EADDRINUSE;
 error_unlock:
        release_sock(&rx->sk);
@@ -906,6 +907,7 @@ static int rxrpc_release_sock(struct sock *sk)
        rxrpc_purge_queue(&sk->sk_receive_queue);
 
        rxrpc_unuse_local(rx->local);
+       rxrpc_put_local(rx->local);
        rx->local = NULL;
        key_put(rx->key);
        rx->key = NULL;

diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index ccef6e40e002060aea2e28576f5ceab507d2ec82..4e47da6ab728463af6a21dbea297cfd27b16cd72 100644 (file)
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -1006,6 +1006,16 @@ void rxrpc_unuse_local(struct rxrpc_local *);
 void rxrpc_queue_local(struct rxrpc_local *);
 void rxrpc_destroy_all_locals(struct rxrpc_net *);
 
+static inline bool __rxrpc_unuse_local(struct rxrpc_local *local)
+{
+       return atomic_dec_return(&local->active_users) == 0;
+}
+
+static inline bool __rxrpc_use_local(struct rxrpc_local *local)
+{
+       return atomic_fetch_add_unless(&local->active_users, 1, 0) != 0;
+}
+
 /*
  * misc.c
  */

diff --git a/net/rxrpc/conn_event.c b/net/rxrpc/conn_event.c
index b6fca8ebb1173f4de1047e96315c26072666c2e9..126154a97a5921697d1c385dec78a3291d19179b 100644 (file)
--- a/net/rxrpc/conn_event.c
+++ b/net/rxrpc/conn_event.c
@@ -453,16 +453,12 @@ again:
 /*
  * connection-level event processor
  */
-void rxrpc_process_connection(struct work_struct *work)
+static void rxrpc_do_process_connection(struct rxrpc_connection *conn)
 {
-       struct rxrpc_connection *conn =
-               container_of(work, struct rxrpc_connection, processor);
        struct sk_buff *skb;
        u32 abort_code = RX_PROTOCOL_ERROR;
        int ret;
 
-       rxrpc_see_connection(conn);
-
        if (test_and_clear_bit(RXRPC_CONN_EV_CHALLENGE, &conn->events))
                rxrpc_secure_connection(conn);
 
@@ -490,18 +486,33 @@ void rxrpc_process_connection(struct work_struct *work)
                }
        }
 
-out:
-       rxrpc_put_connection(conn);
-       _leave("");
        return;
 
 requeue_and_leave:
        skb_queue_head(&conn->rx_queue, skb);
-       goto out;
+       return;
 
 protocol_error:
        if (rxrpc_abort_connection(conn, ret, abort_code) < 0)
                goto requeue_and_leave;
        rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
-       goto out;
+       return;
+}
+
+void rxrpc_process_connection(struct work_struct *work)
+{
+       struct rxrpc_connection *conn =
+               container_of(work, struct rxrpc_connection, processor);
+
+       rxrpc_see_connection(conn);
+
+       if (__rxrpc_use_local(conn->params.local)) {
+               rxrpc_do_process_connection(conn);
+               rxrpc_unuse_local(conn->params.local);
+       }
+
+       rxrpc_put_connection(conn);
+       _leave("");
+       return;
 }
+

diff --git a/net/rxrpc/local_object.c b/net/rxrpc/local_object.c
index 4fe92211c77ff68817215d8c4e4da4001d76070b..4c0087a48e8726919c04b8fa92d3d591905d1101 100644 (file)
--- a/net/rxrpc/local_object.c
+++ b/net/rxrpc/local_object.c
@@ -387,14 +387,11 @@ void rxrpc_put_local(struct rxrpc_local *local)
  */
 struct rxrpc_local *rxrpc_use_local(struct rxrpc_local *local)
 {
-       unsigned int au;
-
        local = rxrpc_get_local_maybe(local);
        if (!local)
                return NULL;
 
-       au = atomic_fetch_add_unless(&local->active_users, 1, 0);
-       if (au == 0) {
+       if (!__rxrpc_use_local(local)) {
                rxrpc_put_local(local);
                return NULL;
        }
@@ -408,14 +405,11 @@ struct rxrpc_local *rxrpc_use_local(struct rxrpc_local *local)
  */
 void rxrpc_unuse_local(struct rxrpc_local *local)
 {
-       unsigned int au;
-
        if (local) {
-               au = atomic_dec_return(&local->active_users);
-               if (au == 0)
+               if (__rxrpc_unuse_local(local)) {
+                       rxrpc_get_local(local);
                        rxrpc_queue_local(local);
-               else
-                       rxrpc_put_local(local);
+               }
        }
 }
 
@@ -472,7 +466,7 @@ static void rxrpc_local_processor(struct work_struct *work)
 
        do {
                again = false;
-               if (atomic_read(&local->active_users) == 0) {
+               if (!__rxrpc_use_local(local)) {
                        rxrpc_local_destroyer(local);
                        break;
                }
@@ -486,6 +480,8 @@ static void rxrpc_local_processor(struct work_struct *work)
                        rxrpc_process_local_events(local);
                        again = true;
                }
+
+               __rxrpc_unuse_local(local);
        } while (again);
 
        rxrpc_put_local(local);

diff --git a/net/rxrpc/peer_event.c b/net/rxrpc/peer_event.c
index 42582a9ff81d3aee99cfdf60b36ea69bd45e5a38..85bdc31d3dbf9e11157a805ec2b404e817198156 100644 (file)
--- a/net/rxrpc/peer_event.c
+++ b/net/rxrpc/peer_event.c
@@ -357,27 +357,31 @@ static void rxrpc_peer_keepalive_dispatch(struct rxrpc_net *rxnet,
                if (!rxrpc_get_peer_maybe(peer))
                        continue;
 
-               spin_unlock_bh(&rxnet->peer_hash_lock);
-
-               keepalive_at = peer->last_tx_at + RXRPC_KEEPALIVE_TIME;
-               slot = keepalive_at - base;
-               _debug("%02x peer %u t=%d {%pISp}",
-                      cursor, peer->debug_id, slot, &peer->srx.transport);
+               if (__rxrpc_use_local(peer->local)) {
+                       spin_unlock_bh(&rxnet->peer_hash_lock);
+
+                       keepalive_at = peer->last_tx_at + RXRPC_KEEPALIVE_TIME;
+                       slot = keepalive_at - base;
+                       _debug("%02x peer %u t=%d {%pISp}",
+                              cursor, peer->debug_id, slot, &peer->srx.transport);
+
+                       if (keepalive_at <= base ||
+                           keepalive_at > base + RXRPC_KEEPALIVE_TIME) {
+                               rxrpc_send_keepalive(peer);
+                               slot = RXRPC_KEEPALIVE_TIME;
+                       }
 
-               if (keepalive_at <= base ||
-                   keepalive_at > base + RXRPC_KEEPALIVE_TIME) {
-                       rxrpc_send_keepalive(peer);
-                       slot = RXRPC_KEEPALIVE_TIME;
+                       /* A transmission to this peer occurred since last we
+                        * examined it so put it into the appropriate future
+                        * bucket.
+                        */
+                       slot += cursor;
+                       slot &= mask;
+                       spin_lock_bh(&rxnet->peer_hash_lock);
+                       list_add_tail(&peer->keepalive_link,
+                                     &rxnet->peer_keepalive[slot & mask]);
+                       rxrpc_unuse_local(peer->local);
                }
-
-               /* A transmission to this peer occurred since last we examined
-                * it so put it into the appropriate future bucket.
-                */
-               slot += cursor;
-               slot &= mask;
-               spin_lock_bh(&rxnet->peer_hash_lock);
-               list_add_tail(&peer->keepalive_link,
-                             &rxnet->peer_keepalive[slot & mask]);
                rxrpc_put_peer_locked(peer);
        }