From: David Howells <dhowells@redhat.com>
Date: Mon, 7 Oct 2019 10:58:29 +0100
Subject: rxrpc: Fix trace-after-put looking at the put connection record
Patch-mainline: v5.4-rc4
Git-commit: 4c1295dccc0afe0905b6ca4c62ade7f2406f2cfb
References: bsc#1154353

rxrpc_put_*conn() calls trace_rxrpc_conn() after they have done the
decrement of the refcount - which looks at the debug_id in the connection
record.  But unless the refcount was reduced to zero, we no longer have the
right to look in the record and, indeed, it may be deleted by some other
thread.

Fix this by getting the debug_id out before decrementing the refcount and
then passing that into the tracepoint.

Fixes: 363deeab6d0f ("rxrpc: Add connection tracepoint and client conn state tracepoint")
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 include/trace/events/rxrpc.h |    6 +++---
 net/rxrpc/call_accept.c      |    2 +-
 net/rxrpc/conn_client.c      |    6 ++++--
 net/rxrpc/conn_object.c      |   13 +++++++------
 net/rxrpc/conn_service.c     |    2 +-
 5 files changed, 16 insertions(+), 13 deletions(-)

--- a/include/trace/events/rxrpc.h
+++ b/include/trace/events/rxrpc.h
@@ -546,10 +546,10 @@ TRACE_EVENT(rxrpc_peer,
 	    );
 
 TRACE_EVENT(rxrpc_conn,
-	    TP_PROTO(struct rxrpc_connection *conn, enum rxrpc_conn_trace op,
+	    TP_PROTO(unsigned int conn_debug_id, enum rxrpc_conn_trace op,
 		     int usage, const void *where),
 
-	    TP_ARGS(conn, op, usage, where),
+	    TP_ARGS(conn_debug_id, op, usage, where),
 
 	    TP_STRUCT__entry(
 		    __field(unsigned int,	conn		)
@@ -559,7 +559,7 @@ TRACE_EVENT(rxrpc_conn,
 			     ),
 
 	    TP_fast_assign(
-		    __entry->conn = conn->debug_id;
+		    __entry->conn = conn_debug_id;
 		    __entry->op = op;
 		    __entry->usage = usage;
 		    __entry->where = where;
--- a/net/rxrpc/call_accept.c
+++ b/net/rxrpc/call_accept.c
@@ -84,7 +84,7 @@ static int rxrpc_service_prealloc_one(st
 		smp_store_release(&b->conn_backlog_head,
 				  (head + 1) & (size - 1));
 
-		trace_rxrpc_conn(conn, rxrpc_conn_new_service,
+		trace_rxrpc_conn(conn->debug_id, rxrpc_conn_new_service,
 				 atomic_read(&conn->usage), here);
 	}
 
--- a/net/rxrpc/conn_client.c
+++ b/net/rxrpc/conn_client.c
@@ -212,7 +212,8 @@ rxrpc_alloc_client_connection(struct rxr
 	rxrpc_get_local(conn->params.local);
 	key_get(conn->params.key);
 
-	trace_rxrpc_conn(conn, rxrpc_conn_new_client, atomic_read(&conn->usage),
+	trace_rxrpc_conn(conn->debug_id, rxrpc_conn_new_client,
+			 atomic_read(&conn->usage),
 			 __builtin_return_address(0));
 	trace_rxrpc_client(conn, -1, rxrpc_client_alloc);
 	_leave(" = %p", conn);
@@ -985,11 +986,12 @@ rxrpc_put_one_client_conn(struct rxrpc_c
 void rxrpc_put_client_conn(struct rxrpc_connection *conn)
 {
 	const void *here = __builtin_return_address(0);
+	unsigned int debug_id = conn->debug_id;
 	int n;
 
 	do {
 		n = atomic_dec_return(&conn->usage);
-		trace_rxrpc_conn(conn, rxrpc_conn_put_client, n, here);
+		trace_rxrpc_conn(debug_id, rxrpc_conn_put_client, n, here);
 		if (n > 0)
 			return;
 		ASSERTCMP(n, >=, 0);
--- a/net/rxrpc/conn_object.c
+++ b/net/rxrpc/conn_object.c
@@ -269,7 +269,7 @@ bool rxrpc_queue_conn(struct rxrpc_conne
 	if (n == 0)
 		return false;
 	if (rxrpc_queue_work(&conn->processor))
-		trace_rxrpc_conn(conn, rxrpc_conn_queued, n + 1, here);
+		trace_rxrpc_conn(conn->debug_id, rxrpc_conn_queued, n + 1, here);
 	else
 		rxrpc_put_connection(conn);
 	return true;
@@ -284,7 +284,7 @@ void rxrpc_see_connection(struct rxrpc_c
 	if (conn) {
 		int n = atomic_read(&conn->usage);
 
-		trace_rxrpc_conn(conn, rxrpc_conn_seen, n, here);
+		trace_rxrpc_conn(conn->debug_id, rxrpc_conn_seen, n, here);
 	}
 }
 
@@ -296,7 +296,7 @@ void rxrpc_get_connection(struct rxrpc_c
 	const void *here = __builtin_return_address(0);
 	int n = atomic_inc_return(&conn->usage);
 
-	trace_rxrpc_conn(conn, rxrpc_conn_got, n, here);
+	trace_rxrpc_conn(conn->debug_id, rxrpc_conn_got, n, here);
 }
 
 /*
@@ -310,7 +310,7 @@ rxrpc_get_connection_maybe(struct rxrpc_
 	if (conn) {
 		int n = atomic_fetch_add_unless(&conn->usage, 1, 0);
 		if (n > 0)
-			trace_rxrpc_conn(conn, rxrpc_conn_got, n + 1, here);
+			trace_rxrpc_conn(conn->debug_id, rxrpc_conn_got, n + 1, here);
 		else
 			conn = NULL;
 	}
@@ -333,10 +333,11 @@ static void rxrpc_set_service_reap_timer
 void rxrpc_put_service_conn(struct rxrpc_connection *conn)
 {
 	const void *here = __builtin_return_address(0);
+	unsigned int debug_id = conn->debug_id;
 	int n;
 
 	n = atomic_dec_return(&conn->usage);
-	trace_rxrpc_conn(conn, rxrpc_conn_put_service, n, here);
+	trace_rxrpc_conn(debug_id, rxrpc_conn_put_service, n, here);
 	ASSERTCMP(n, >=, 0);
 	if (n == 1)
 		rxrpc_set_service_reap_timer(conn->params.local->rxnet,
@@ -420,7 +421,7 @@ void rxrpc_service_connection_reaper(str
 		 */
 		if (atomic_cmpxchg(&conn->usage, 1, 0) != 1)
 			continue;
-		trace_rxrpc_conn(conn, rxrpc_conn_reap_service, 0, NULL);
+		trace_rxrpc_conn(conn->debug_id, rxrpc_conn_reap_service, 0, NULL);
 
 		if (rxrpc_conn_is_client(conn))
 			BUG();
--- a/net/rxrpc/conn_service.c
+++ b/net/rxrpc/conn_service.c
@@ -134,7 +134,7 @@ struct rxrpc_connection *rxrpc_prealloc_
 		list_add_tail(&conn->proc_link, &rxnet->conn_proc_list);
 		write_unlock(&rxnet->conn_lock);
 
-		trace_rxrpc_conn(conn, rxrpc_conn_new_service,
+		trace_rxrpc_conn(conn->debug_id, rxrpc_conn_new_service,
 				 atomic_read(&conn->usage),
 				 __builtin_return_address(0));
 	}