[PATCH v3] block: add capacity validation in bdev_add_partition()

["min.li" <min15.li@samsung.com>]

In the function bdev_add_partition(),there is no check that the start
and end sectors exceed the size of the disk before calling add_partition.
When we call the block's ioctl interface directly to add a partition,
and the capacity of the disk is set to 0 by driver,the command will
continue to execute.

Signed-off-by: min.li <min15.li@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

---
Changes from v1:

- Check for overflows of the start + length value.
- Place the capacity check at the beginning of the function.

Changes from v2:

- Place the assignment on the first line and merge the two lines into one.
- Modify the singed name.
---
 block/partitions/core.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/block/partitions/core.c b/block/partitions/core.c
index 49e0496ff23c..b511f88bf558 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -436,10 +436,21 @@ static bool partition_overlaps(struct gendisk *disk, sector_t start,
 int bdev_add_partition(struct gendisk *disk, int partno, sector_t start,
 		sector_t length)
 {
+	sector_t capacity = get_capacity(disk), end;
 	struct block_device *part;
 	int ret;
 
 	mutex_lock(&disk->open_mutex);
+	if (check_add_overflow(start, length, &end)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (start >= capacity || end > capacity) {
+		ret = -EINVAL;
+		goto out;
+	}
+
 	if (!disk_live(disk)) {
 		ret = -ENXIO;
 		goto out;
-- 
2.34.1