target: Add range checking to UNMAP emulation

When processing an UNMAP command, we need to make sure that the number
of blocks we're asked to UNMAP does not exceed our reported maximum
number of blocks per UNMAP, and that the range of blocks we're
unmapping doesn't go past the end of the device.

Signed-off-by: Roland Dreier <roland@purestorage.com>
Cc: stable@vger.kernel.org
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_iblock.c

@@ -348,6 +348,18 @@ static int iblock_execute_unmap(struct se_cmd *cmd)
 		pr_debug("UNMAP: Using lba: %llu and range: %u\n",
 				 (unsigned long long)lba, range);
 
+		if (range > dev->se_sub_dev->se_dev_attrib.max_unmap_lba_count) {
+			cmd->scsi_sense_reason = TCM_INVALID_PARAMETER_LIST;
+			ret = -EINVAL;
+			goto err;
+		}
+
+		if (lba + range > dev->transport->get_blocks(dev) + 1) {
+			cmd->scsi_sense_reason = TCM_ADDRESS_OUT_OF_RANGE;
+			ret = -EINVAL;
+			goto err;
+		}
+
 		ret = blkdev_issue_discard(ibd->ibd_bd, lba, range,
 					   GFP_KERNEL, 0);
 		if (ret < 0) {