sd: get disk reference in sd_check_events()

sd_check_events() is called asynchronously, and might race
with device removal. So always take a disk reference when
processing the event to avoid the device being removed while
the event is processed.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 428c03ef02b2..f459dff30512 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1398,11 +1398,15 @@ static int media_not_present(struct scsi_disk *sdkp,
  **/
 static unsigned int sd_check_events(struct gendisk *disk, unsigned int clearing)
 {
-        struct scsi_disk *sdkp = scsi_disk(disk);
-        struct scsi_device *sdp = sdkp->device;
+        struct scsi_disk *sdkp = scsi_disk_get(disk);
+        struct scsi_device *sdp;
         struct scsi_sense_hdr *sshdr = NULL;
         int retval;
 
+        if (!sdkp)
+                return 0;
+
+        sdp = sdkp->device;
         SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp, "sd_check_events\n"));
 
         /*
@@ -1459,6 +1463,7 @@ out:
         kfree(sshdr);
         retval = sdp->changed ? DISK_EVENT_MEDIA_CHANGE : 0;
         sdp->changed = 0;
+        scsi_disk_put(sdkp);
         return retval;
 }