rxrpc: Make /proc/net/rxrpc_calls safer

Make /proc/net/rxrpc_calls safer by stashing a copy of the peer pointer in
the rxrpc_call struct and checking in the show routine that the peer
pointer, the socket pointer and the local pointer obtained from the socket
pointer aren't NULL before we use them.
Signed-off-by: David Howells <dhowells@redhat.com>

net/rxrpc/ar-internal.h

@@ -407,6 +407,7 @@ enum rxrpc_call_state {
 struct rxrpc_call {
 	struct rcu_head		rcu;
 	struct rxrpc_connection	*conn;		/* connection carrying call */
+	struct rxrpc_peer	*peer;		/* Peer record for remote address */
 	struct rxrpc_sock	*socket;	/* socket responsible */
 	struct timer_list	lifetimer;	/* lifetime remaining on call */
 	struct timer_list	deadspan;	/* reap timer for re-ACK'ing, etc  */
@@ -717,9 +718,10 @@ struct rxrpc_peer *rxrpc_lookup_peer(struct rxrpc_local *,
 				     struct sockaddr_rxrpc *, gfp_t);
 struct rxrpc_peer *rxrpc_alloc_peer(struct rxrpc_local *, gfp_t);
 
-static inline void rxrpc_get_peer(struct rxrpc_peer *peer)
+static inline struct rxrpc_peer *rxrpc_get_peer(struct rxrpc_peer *peer)
 {
 	atomic_inc(&peer->usage);
+	return peer;
 }
 
 static inline

net/rxrpc/call_object.c

@@ -315,6 +315,7 @@ struct rxrpc_call *rxrpc_incoming_call(struct rxrpc_sock *rx,
 	chan = sp->hdr.cid & RXRPC_CHANNELMASK;
 	candidate->socket	= rx;
 	candidate->conn		= conn;
+	candidate->peer		= conn->params.peer;
 	candidate->cid		= sp->hdr.cid;
 	candidate->call_id	= sp->hdr.callNumber;
 	candidate->rx_data_post	= 0;
@@ -384,6 +385,7 @@ struct rxrpc_call *rxrpc_incoming_call(struct rxrpc_sock *rx,
 	rcu_assign_pointer(conn->channels[chan].call, call);
 	sock_hold(&rx->sk);
 	rxrpc_get_connection(conn);
+	rxrpc_get_peer(call->peer);
 	spin_unlock(&conn->channel_lock);
 
 	spin_lock(&conn->params.peer->lock);
@@ -610,6 +612,7 @@ static void rxrpc_rcu_destroy_call(struct rcu_head *rcu)
 	struct rxrpc_call *call = container_of(rcu, struct rxrpc_call, rcu);
 
 	rxrpc_purge_queue(&call->rx_queue);
+	rxrpc_put_peer(call->peer);
 	kmem_cache_free(rxrpc_call_jar, call);
 }
 

net/rxrpc/conn_client.c

@@ -280,6 +280,7 @@ int rxrpc_connect_call(struct rxrpc_call *call,
 found_channel:
 	_debug("found chan");
 	call->conn	= conn;
+	call->peer	= rxrpc_get_peer(conn->params.peer);
 	call->cid	= conn->proto.cid | chan;
 	call->call_id	= ++conn->channels[chan].call_counter;
 	conn->channels[chan].call_id = call->call_id;

net/rxrpc/proc.c

@@ -46,7 +46,9 @@ static void rxrpc_call_seq_stop(struct seq_file *seq, void *v)
 
 static int rxrpc_call_seq_show(struct seq_file *seq, void *v)
 {
-	struct rxrpc_connection *conn;
+	struct rxrpc_local *local;
+	struct rxrpc_sock *rx;
+	struct rxrpc_peer *peer;
 	struct rxrpc_call *call;
 	char lbuff[4 + 4 + 4 + 4 + 5 + 1], rbuff[4 + 4 + 4 + 4 + 5 + 1];
 
@@ -60,15 +62,24 @@ static int rxrpc_call_seq_show(struct seq_file *seq, void *v)
 
 	call = list_entry(v, struct rxrpc_call, link);
 
-	sprintf(lbuff, "%pI4:%u",
-		&call->socket->local->srx.transport.sin.sin_addr,
-		ntohs(call->socket->local->srx.transport.sin.sin_port));
+	rx = READ_ONCE(call->socket);
+	if (rx) {
+		local = READ_ONCE(rx->local);
+		if (local)
+			sprintf(lbuff, "%pI4:%u",
+				&local->srx.transport.sin.sin_addr,
+				ntohs(local->srx.transport.sin.sin_port));
+		else
+			strcpy(lbuff, "no_local");
+	} else {
+		strcpy(lbuff, "no_socket");
+	}
 
-	conn = call->conn;
-	if (conn)
+	peer = call->peer;
+	if (peer)
 		sprintf(rbuff, "%pI4:%u",
-			&conn->params.peer->srx.transport.sin.sin_addr,
-			ntohs(conn->params.peer->srx.transport.sin.sin_port));
+			&peer->srx.transport.sin.sin_addr,
+			ntohs(peer->srx.transport.sin.sin_port));
 	else
 		strcpy(rbuff, "no_connection");