ses: Fix problems with simple enclosures

commit 3417c1b5 upstream.

Simple enclosure implementations (mostly USB) are allowed to return only
page 8 to every diagnostic query.  That really confuses our
implementation because we assume the return is the page we asked for and
end up doing incorrect offsets based on bogus information leading to
accesses outside of allocated ranges.  Fix that by checking the page
code of the return and giving an error if it isn't the one we asked for.
This should fix reported bugs with USB storage by simply refusing to
attach to enclosures that behave like this.  It's also good defensive
practise now that we're starting to see more USB enclosures.
Reported-by: Andrea Gelmini <andrea.gelmini@gelma.net>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/scsi/ses.c

@@ -70,6 +70,7 @@ static int ses_probe(struct device *dev)
 static int ses_recv_diag(struct scsi_device *sdev, int page_code,
 			 void *buf, int bufflen)
 {
+	int ret;
 	unsigned char cmd[] = {
 		RECEIVE_DIAGNOSTIC,
 		1,		/* Set PCV bit */
@@ -78,9 +79,26 @@ static int ses_recv_diag(struct scsi_device *sdev, int page_code,
 		bufflen & 0xff,
 		0
 	};
+	unsigned char recv_page_code;
 
-	return scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buf, bufflen,
+	ret =  scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buf, bufflen,
 				NULL, SES_TIMEOUT, SES_RETRIES, NULL);
+	if (unlikely(!ret))
+		return ret;
+
+	recv_page_code = ((unsigned char *)buf)[0];
+
+	if (likely(recv_page_code == page_code))
+		return ret;
+
+	/* successful diagnostic but wrong page code.  This happens to some
+	 * USB devices, just print a message and pretend there was an error */
+
+	sdev_printk(KERN_ERR, sdev,
+		    "Wrong diagnostic page; asked for %d got %u\n",
+		    page_code, recv_page_code);
+
+	return -EINVAL;
 }
 
 static int ses_send_diag(struct scsi_device *sdev, int page_code,