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, 10 insertions, 39 deletions

diff --git a/net/rxrpc/conn_event.c b/net/rxrpc/conn_event.c
index 8d0b9ff0a5e1..44414e724415 100644
--- a/net/rxrpc/conn_event.c
+++ b/net/rxrpc/conn_event.c
@@ -100,9 +100,7 @@ void rxrpc_conn_retransmit_call(struct rxrpc_connection *conn,
 	/* If the last call got moved on whilst we were waiting to run, just
 	 * ignore this packet.
 	 */
-	call_id = READ_ONCE(chan->last_call);
-	/* Sync with __rxrpc_disconnect_call() */
-	smp_rmb();
+	call_id = chan->last_call;
 	if (skb && call_id != sp->hdr.callNumber)
 		return;
 
@@ -119,9 +117,12 @@ void rxrpc_conn_retransmit_call(struct rxrpc_connection *conn,
 	iov[2].iov_base	= &ack_info;
 	iov[2].iov_len	= sizeof(ack_info);
 
+	serial = atomic_inc_return(&conn->serial);
+
 	pkt.whdr.epoch		= htonl(conn->proto.epoch);
 	pkt.whdr.cid		= htonl(conn->proto.cid | channel);
 	pkt.whdr.callNumber	= htonl(call_id);
+	pkt.whdr.serial		= htonl(serial);
 	pkt.whdr.seq		= 0;
 	pkt.whdr.type		= chan->last_type;
 	pkt.whdr.flags		= conn->out_clientflag;
@@ -158,31 +159,15 @@ void rxrpc_conn_retransmit_call(struct rxrpc_connection *conn,
 		iov[0].iov_len += sizeof(pkt.ack);
 		len += sizeof(pkt.ack) + 3 + sizeof(ack_info);
 		ioc = 3;
-		break;
-
-	default:
-		return;
-	}
-
-	/* Resync with __rxrpc_disconnect_call() and check that the last call
-	 * didn't get advanced whilst we were filling out the packets.
-	 */
-	smp_rmb();
-	if (READ_ONCE(chan->last_call) != call_id)
-		return;
-
-	serial = atomic_inc_return(&conn->serial);
-	pkt.whdr.serial = htonl(serial);
 
-	switch (chan->last_type) {
-	case RXRPC_PACKET_TYPE_ABORT:
-		break;
-	case RXRPC_PACKET_TYPE_ACK:
 		trace_rxrpc_tx_ack(chan->call_debug_id, serial,
 				   ntohl(pkt.ack.firstPacket),
 				   ntohl(pkt.ack.serial),
 				   pkt.ack.reason, 0);
 		break;
+
+	default:
+		return;
 	}
 
 	ret = kernel_sendmsg(conn->local->socket, &msg, iov, ioc, len);
@@ -207,12 +192,8 @@ static void rxrpc_abort_calls(struct rxrpc_connection *conn)
 
 	_enter("{%d},%x", conn->debug_id, conn->abort_code);
 
-	spin_lock(&conn->bundle->channel_lock);
-
 	for (i = 0; i < RXRPC_MAXCALLS; i++) {
-		call = rcu_dereference_protected(
-			conn->channels[i].call,
-			lockdep_is_held(&conn->bundle->channel_lock));
+		call = conn->channels[i].call;
 		if (call)
 			rxrpc_set_call_completion(call,
 						  conn->completion,
@@ -220,7 +201,6 @@ static void rxrpc_abort_calls(struct rxrpc_connection *conn)
 						  conn->error);
 	}
 
-	spin_unlock(&conn->bundle->channel_lock);
 	_leave("");
 }
 
@@ -316,9 +296,7 @@ again:
 		if (!test_bit(RXRPC_CONN_FINAL_ACK_0 + channel, &conn->flags))
 			continue;
 
-		smp_rmb(); /* vs rxrpc_disconnect_client_call */
-		ack_at = READ_ONCE(chan->final_ack_at);
-
+		ack_at = chan->final_ack_at;
 		if (time_before(j, ack_at) && !force) {
 			if (time_before(ack_at, next_j)) {
 				next_j = ack_at;
@@ -446,15 +424,8 @@ void rxrpc_input_conn_event(struct rxrpc_connection *conn, struct sk_buff *skb)
 		if (conn->state != RXRPC_CONN_SERVICE)
 			break;
 
-		spin_lock(&conn->bundle->channel_lock);
-
 		for (loop = 0; loop < RXRPC_MAXCALLS; loop++)
-			rxrpc_call_is_secure(
-				rcu_dereference_protected(
-					conn->channels[loop].call,
-					lockdep_is_held(&conn->bundle->channel_lock)));
-
-		spin_unlock(&conn->bundle->channel_lock);
+			rxrpc_call_is_secure(conn->channels[loop].call);
 		break;
 	}