diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 572673873ddf..701d8e8480f2 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2075,7 +2075,7 @@ EXPORT_SYMBOL_GPL(scsi_mode_select);
 /**
  *	scsi_mode_sense - issue a mode sense, falling back from 10 to six bytes if necessary.
  *	@sdev:	SCSI device to be queried
- *	@dbd:	set if mode sense will allow block descriptors to be returned
+ *	@dbd:	set to prevent mode sense from returning block descriptors
  *	@modepage: mode page being requested
  *	@buffer: request buffer (may not be smaller than eight bytes)
  *	@len:	length of request buffer.
@@ -2110,18 +2110,18 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
 		sshdr = &my_sshdr;
 
  retry:
-	use_10_for_ms = sdev->use_10_for_ms;
+	use_10_for_ms = sdev->use_10_for_ms || len > 255;
 
 	if (use_10_for_ms) {
-		if (len < 8)
-			len = 8;
+		if (len < 8 || len > 65535)
+			return -EINVAL;
 
 		cmd[0] = MODE_SENSE_10;
-		cmd[8] = len;
+		put_unaligned_be16(len, &cmd[7]);
 		header_length = 8;
 	} else {
 		if (len < 4)
-			len = 4;
+			return -EINVAL;
 
 		cmd[0] = MODE_SENSE;
 		cmd[4] = len;
@@ -2145,9 +2145,15 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
 			if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
 			    (sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
 				/*
-				 * Invalid command operation code
+				 * Invalid command operation code: retry using
+				 * MODE SENSE(6) if this was a MODE SENSE(10)
+				 * request, except if the request mode page is
+				 * too large for MODE SENSE single byte
+				 * allocation length field.
 				 */
 				if (use_10_for_ms) {
+					if (len > 255)
+						return -EIO;
 					sdev->use_10_for_ms = 0;
 					goto retry;
 				}
@@ -2171,12 +2177,11 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
 		data->longlba = 0;
 		data->block_descriptor_length = 0;
 	} else if (use_10_for_ms) {
-		data->length = buffer[0]*256 + buffer[1] + 2;
+		data->length = get_unaligned_be16(&buffer[0]) + 2;
 		data->medium_type = buffer[2];
 		data->device_specific = buffer[3];
 		data->longlba = buffer[4] & 0x01;
-		data->block_descriptor_length = buffer[6]*256
-			+ buffer[7];
+		data->block_descriptor_length = get_unaligned_be16(&buffer[6]);
 	} else {
 		data->length = buffer[0] + 1;
 		data->medium_type = buffer[1];