scsi: ses: Don't attach if enclosure has no components

An enclosure with no components can't usefully be operated by the driver
(since effectively it has nothing to manage), so report the problem and
don't attach. Not attaching also fixes an oops which could occur if the
driver tries to manage a zero component enclosure.

[mkp: Switched to KERN_WARNING since this scenario is common]

Link: https://lore.kernel.org/r/c5deac044ac409e32d9ad9968ce0dcbc996bfc7a.camel@linux.ibm.com
Cc: stable@vger.kernel.org
Reported-by: Ding Hui <dinghui@sangfor.com.cn>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ses.c

@@ -733,6 +733,12 @@ static int ses_intf_add(struct device *cdev,
 		    type_ptr[0] == ENCLOSURE_COMPONENT_ARRAY_DEVICE)
 			components += type_ptr[1];
 	}
+
+	if (components == 0) {
+		sdev_printk(KERN_WARNING, sdev, "enclosure has no enumerated components\n");
+		goto err_free;
+	}
+
 	ses_dev->page1 = buf;
 	ses_dev->page1_len = len;
 	buf = NULL;