rds: cancel send/recv work before queuing connection shutdown

We could end up executing rds_conn_shutdown before the rds_recv_worker
thread, then rds_conn_shutdown -> rds_tcp_conn_shutdown can do a
sock_release and set sock->sk to null, which may interleave in bad
ways with rds_recv_worker, e.g., it could result in:

"BUG: unable to handle kernel NULL pointer dereference at 0000000000000078"
    [ffff881769f6fd70] release_sock at ffffffff815f337b
    [ffff881769f6fd90] rds_tcp_recv at ffffffffa043c888 [rds_tcp]
    [ffff881769f6fdb0] rds_recv_worker at ffffffffa04a4810 [rds]
    [ffff881769f6fde0] process_one_work at ffffffff810a14c1
    [ffff881769f6fe40] worker_thread at ffffffff810a1940
    [ffff881769f6fec0] kthread at ffffffff810a6b1e

Also, do not enqueue any new shutdown workq items when the connection is
shutting down (this may happen for rds-tcp in softirq mode, if a FIN
or CLOSE is received while the modules is in the middle of an unload)

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 6 deletions

diff --git a/net/rds/connection.c b/net/rds/connection.c
index 50a3789..005bca6 100644
--- a/net/rds/connection.c
+++ b/net/rds/connection.c
@@ -374,13 +374,13 @@ static void rds_conn_path_destroy(struct rds_conn_path *cp)
 	if (!cp->cp_transport_data)
 		return;
 
-	rds_conn_path_drop(cp);
-	flush_work(&cp->cp_down_w);
-
 	/* make sure lingering queued work won't try to ref the conn */
 	cancel_delayed_work_sync(&cp->cp_send_w);
 	cancel_delayed_work_sync(&cp->cp_recv_w);
 
+	rds_conn_path_drop(cp, true);
+	flush_work(&cp->cp_down_w);
+
 	/* tear down queued messages */
 	list_for_each_entry_safe(rm, rtmp,
 				 &cp->cp_send_queue,
@@ -664,9 +664,13 @@ void rds_conn_exit(void)
 /*
  * Force a disconnect
  */
-void rds_conn_path_drop(struct rds_conn_path *cp)
+void rds_conn_path_drop(struct rds_conn_path *cp, bool destroy)
 {
 	atomic_set(&cp->cp_state, RDS_CONN_ERROR);
+
+	if (!destroy && cp->cp_conn->c_destroy_in_prog)
+		return;
+
 	queue_work(rds_wq, &cp->cp_down_w);
 }
 EXPORT_SYMBOL_GPL(rds_conn_path_drop);
@@ -674,7 +678,7 @@ EXPORT_SYMBOL_GPL(rds_conn_path_drop);
 void rds_conn_drop(struct rds_connection *conn)
 {
 	WARN_ON(conn->c_trans->t_mp_capable);
-	rds_conn_path_drop(&conn->c_path[0]);
+	rds_conn_path_drop(&conn->c_path[0], false);
 }
 EXPORT_SYMBOL_GPL(rds_conn_drop);
 
@@ -706,5 +710,5 @@ __rds_conn_path_error(struct rds_conn_path *cp, const char *fmt, ...)
 	vprintk(fmt, ap);
 	va_end(ap);
 
-	rds_conn_path_drop(cp);
+	rds_conn_path_drop(cp, false);
 }