scsi: sr: Fix sshdr use in sr_get_events

If scsi_execute_cmd returns < 0, it doesn't initialize the sshdr, so we
shouldn't access the sshdr. If it returns 0, then the cmd executed
successfully, so there is no need to check the sshdr. This has us access
the sshdr when we get a return value > 0.

Signed-off-by: Mike Christie <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: John Garry <[email protected]>
Reviewed-by: Martin Wilck <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>

Author: mikechristie

drivers/scsi/sr.c

@@ -177,7 +177,8 @@ static unsigned int sr_get_events(struct scsi_device *sdev)
 
 	result = scsi_execute_cmd(sdev, cmd, REQ_OP_DRV_IN, buf, sizeof(buf),
 				  SR_TIMEOUT, MAX_RETRIES, &exec_args);
-	if (scsi_sense_valid(&sshdr) && sshdr.sense_key == UNIT_ATTENTION)
+	if (result > 0 && scsi_sense_valid(&sshdr) &&
+	    sshdr.sense_key == UNIT_ATTENTION)
 		return DISK_EVENT_MEDIA_CHANGE;
 
 	if (result || be16_to_cpu(eh->data_len) < sizeof(*med))