[PATCH -next v2] block: Fix the partition start may overflow in add_partition()

[Zhong Jinghua]

In the blkdev_ioctl, we can pass in the unsigned number 0x8000000000000000
as an input parameter, like below:

blkdev_ioctl
  blkpg_ioctl
    blkpg_do_ioctl
      start = p.start >> SECTOR_SHIFT; // start = 0x8000000000000000 >> 9
       bdev_add_partition
         add_partition
           p->start_sect = start; // start = 0xffc0000000000000

Then, there was an warning when submit bio:

submit_bio_noacct
  submit_bio_checks
    blk_partition_remap
      bio->bi_iter.bi_sector += p->start_sect
      // bio->bi_iter.bi_sector = 0xffc0000000000000 + 0xfc00
..
loop_process_work
 loop_handle_cmd
  do_req_filebacked
   pos = ((loff_t) blk_rq_pos(rq) << 9) + lo->lo_offset
   // pos is 0xffc000000000fc00 << 9
   lo_rw_aio
     call_read_iter
      ext4_dio_read_iter
	ext4_dio_read_iter
          iomap_dio_rw
            __iomap_dio_rw
	      iomap_iter
		ext4_iomap_begin
		  map.m_lblk = offset >> blkbits // (u32) map.m_lblk is 0xfc00
		  ext4_set_iomap
		    iomap->offset = (u64) map->m_lblk << blkbits
		    // iomap->offset = 0xfc00
		iomap_iter_done
		  WARN_ON_ONCE(iter->iomap.offset > iter->pos);
		  // iomap.offset = 0xfc00 and iter->pos < 0

This is unreasonable for start + length > disk->part0.nr_sects. There is
already a similar check in blk_add_partition().
Fix it by adding a check in blkpg_do_ioctl().

Reported-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
Signed-off-by: Zhong Jinghua <zhongjinghua@xxxxxxxxxx>
---
 v2: Modify the io stack in commit message.
 block/ioctl.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/block/ioctl.c b/block/ioctl.c
index 9c5f637ff153..3223ea862523 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -33,9 +33,16 @@ static int blkpg_do_ioctl(struct block_device *bdev,
 	if (op == BLKPG_DEL_PARTITION)
 		return bdev_del_partition(disk, p.pno);
 
+	if (p.start < 0 || p.length <= 0 || p.start + p.length < 0)
+		return -EINVAL;
+
 	start = p.start >> SECTOR_SHIFT;
 	length = p.length >> SECTOR_SHIFT;
 
+	/* length may be equal to 0 after right shift */
+	if (!length || start + length > get_capacity(bdev->bd_disk))
+		return -EINVAL;
+
 	switch (op) {
 	case BLKPG_ADD_PARTITION:
 		/* check if partition is aligned to blocksize */
-- 
2.31.1