scsi: scsi_dh_alua: Fix memory leak in alua_rtpg()

buff should be freed before returning with SCSI_DH_RETRY in alua_rtpg().
Signed-off-by: Ntang.junhui <tang.junhui@zte.com.cn>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/device_handler/scsi_dh_alua.c

@@ -583,6 +583,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 			sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
 				    ALUA_DH_NAME);
 			scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
+			kfree(buff);
 			return err;
 		}
 		sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",