[SCSI] zfcp: invalid usage after free of port resources

In certain error scenarios ports, rports are getting attached,
validated and removed from the systems environment. Depending on the
layer this occurs asynchronously. This patch fixes the few races
which existed and ensures all references and cross references are
cleared at the time they're invalid. In addition fc transports
actions are only scheduled when required.

Signed-off-by: Swen Schillig <swen@vnet.ibm.com>
Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

2 files changed, 9 insertions, 4 deletions

diff --git a/drivers/s390/scsi/zfcp_aux.c b/drivers/s390/scsi/zfcp_aux.c
index 2ccbd185a5fb..fa2460b42298 100644
--- a/drivers/s390/scsi/zfcp_aux.c
+++ b/drivers/s390/scsi/zfcp_aux.c
@@ -672,12 +672,15 @@ err_out:
  */
 void zfcp_port_dequeue(struct zfcp_port *port)
 {
-        wait_event(port->remove_wq, atomic_read(&port->refcount) == 0);
         write_lock_irq(&zfcp_data.config_lock);
         list_del(&port->list);
         write_unlock_irq(&zfcp_data.config_lock);
-        if (port->rport)
+        if (port->rport) {
                 port->rport->dd_data = NULL;
+                port->rport = NULL;
+        }
+        wait_event(port->remove_wq, atomic_read(&port->refcount) == 0);
+        cancel_work_sync(&port->rport_work); /* usually not necessary */
         zfcp_adapter_put(port->adapter);
         sysfs_remove_group(&port->sysfs_device.kobj, &zfcp_sysfs_port_attrs);
         device_unregister(&port->sysfs_device);
diff --git a/drivers/s390/scsi/zfcp_scsi.c b/drivers/s390/scsi/zfcp_scsi.c
index 6925a1784682..54a7a7474aa5 100644
--- a/drivers/s390/scsi/zfcp_scsi.c
+++ b/drivers/s390/scsi/zfcp_scsi.c
@@ -582,8 +582,10 @@ void zfcp_scsi_schedule_rport_block(struct zfcp_port *port)
         zfcp_port_get(port);
         port->rport_task = RPORT_DEL;
 
-        if (!queue_work(zfcp_data.work_queue, &port->rport_work))
-                zfcp_port_put(port);
+        if (port->rport && queue_work(zfcp_data.work_queue, &port->rport_work))
+                return;
+
+        zfcp_port_put(port);
 }
 
 void zfcp_scsi_schedule_rports_block(struct zfcp_adapter *adapter)