rxrpc: Move client call connection to the I/O thread

Move the connection setup of client calls to the I/O thread so that a whole
load of locking and barrierage can be eliminated.  This necessitates the
app thread waiting for connection to complete before it can begin
encrypting data.

This also completes the fix for a race that exists between call connection
and call disconnection whereby the data transmission code adds the call to
the peer error distribution list after the call has been disconnected (say
by the rxrpc socket getting closed).

The fix is to complete the process of moving call connection, data
transmission and call disconnection into the I/O thread and thus forcibly
serialising them.

Note that the issue may predate the overhaul to an I/O thread model that
were included in the merge window for v6.2, but the timing is very much
changed by the change given below.

Fixes: cf37b5987508 ("rxrpc: Move DATA transmission into call processor work item")
Reported-by: syzbot+c22650d2844392afdcfd@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org

1 files changed, 7 insertions, 12 deletions

diff --git a/net/rxrpc/conn_object.c b/net/rxrpc/conn_object.c
index 3d8c1dc6a82a..ac85d4644a3c 100644
--- a/net/rxrpc/conn_object.c
+++ b/net/rxrpc/conn_object.c
@@ -67,6 +67,7 @@ struct rxrpc_connection *rxrpc_alloc_connection(struct rxrpc_net *rxnet,
 		INIT_WORK(&conn->destructor, rxrpc_clean_up_connection);
 		INIT_LIST_HEAD(&conn->proc_link);
 		INIT_LIST_HEAD(&conn->link);
+		mutex_init(&conn->security_lock);
 		skb_queue_head_init(&conn->rx_queue);
 		conn->rxnet = rxnet;
 		conn->security = &rxrpc_no_security;
@@ -157,7 +158,7 @@ void __rxrpc_disconnect_call(struct rxrpc_connection *conn,
 
 	_enter("%d,%x", conn->debug_id, call->cid);
 
-	if (rcu_access_pointer(chan->call) == call) {
+	if (chan->call == call) {
 		/* Save the result of the call so that we can repeat it if necessary
 		 * through the channel, whilst disposing of the actual call record.
 		 */
@@ -177,12 +178,9 @@ void __rxrpc_disconnect_call(struct rxrpc_connection *conn,
 			break;
 		}
 
-		/* Sync with rxrpc_conn_retransmit(). */
-		smp_wmb();
 		chan->last_call = chan->call_id;
 		chan->call_id = chan->call_counter;
-
-		rcu_assign_pointer(chan->call, NULL);
+		chan->call = NULL;
 	}
 
 	_leave("");
@@ -210,10 +208,7 @@ void rxrpc_disconnect_call(struct rxrpc_call *call)
 	if (rxrpc_is_client_call(call)) {
 		rxrpc_disconnect_client_call(call->bundle, call);
 	} else {
-		spin_lock(&conn->bundle->channel_lock);
 		__rxrpc_disconnect_call(conn, call);
-		spin_unlock(&conn->bundle->channel_lock);
-
 		conn->idle_timestamp = jiffies;
 		if (atomic_dec_and_test(&conn->active))
 			rxrpc_set_service_reap_timer(conn->rxnet,
@@ -316,10 +311,10 @@ static void rxrpc_clean_up_connection(struct work_struct *work)
 		container_of(work, struct rxrpc_connection, destructor);
 	struct rxrpc_net *rxnet = conn->rxnet;
 
-	ASSERT(!rcu_access_pointer(conn->channels[0].call) &&
-	       !rcu_access_pointer(conn->channels[1].call) &&
-	       !rcu_access_pointer(conn->channels[2].call) &&
-	       !rcu_access_pointer(conn->channels[3].call));
+	ASSERT(!conn->channels[0].call &&
+	       !conn->channels[1].call &&
+	       !conn->channels[2].call &&
+	       !conn->channels[3].call);
 	ASSERT(list_empty(&conn->cache_link));
 
 	del_timer_sync(&conn->timer);