[S390] dasd: fix reference counting in display method for proc/dasd/devices

Using the /proc/dasd/devices interface leaves the reference counter
of alias devices in an inconsistent state. A process that tries to set
such a device offline afterwards will hang.
The dasd_devices_show function returns immediately for alias devices
and this code path was missing a dasd_put_device call.

Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/s390/block/dasd_proc.c b/drivers/s390/block/dasd_proc.c
index 28a86f070048..556063e8f7a9 100644
--- a/drivers/s390/block/dasd_proc.c
+++ b/drivers/s390/block/dasd_proc.c
@@ -62,8 +62,10 @@ dasd_devices_show(struct seq_file *m, void *v)
                 return 0;
         if (device->block)
                 block = device->block;
-        else
+        else {
+                dasd_put_device(device);
                 return 0;
+        }
         /* Print device number. */
         seq_printf(m, "%s", device->cdev->dev.bus_id);
         /* Print discipline string. */