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

[Zhong Jinghua]

From: Zhong Jinghua <zhongjinghua@xxxxxxxxxx>

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

block_ioctl
  blkdev_ioctl
    blkpg_ioctl
      blkpg_do_ioctl
        copy_from_user
        bdev_add_partition
          add_partition
            p->start_sect = start; // start = 0x8000000000000000

Then, there was an warning when submit bio:

WARNING: CPU: 0 PID: 382 at fs/iomap/apply.c:54
Call trace:
 iomap_apply+0x644/0x6e0
 __iomap_dio_rw+0x5cc/0xa24
 iomap_dio_rw+0x4c/0xcc
 ext4_dio_read_iter
 ext4_file_read_iter
 ext4_file_read_iter+0x318/0x39c
 call_read_iter
 lo_rw_aio.isra.0+0x748/0x75c
 do_req_filebacked+0x2d4/0x370
 loop_handle_cmd
 loop_queue_work+0x94/0x23c
 kthread_worker_fn+0x160/0x6bc
 loop_kthread_worker_fn+0x3c/0x50
 kthread+0x20c/0x25c
 ret_from_fork+0x10/0x18

Stack:

submit_bio_noacct
  submit_bio_checks
    blk_partition_remap
      bio->bi_iter.bi_sector += p->start_sect
      // bio->bi_iter.bi_sector = 0xffc0000000000000 + 65408
..
loop_queue_work
 loop_handle_cmd
  do_req_filebacked
   pos = ((loff_t) blk_rq_pos(rq) << 9) + lo->lo_offset // pos < 0
   lo_rw_aio
     call_read_iter
      ext4_dio_read_iter
       __iomap_dio_rw
        iomap_apply
         ext4_iomap_begin
           map.m_lblk = offset >> blkbits
             ext4_set_iomap
             iomap->offset = (u64) map->m_lblk << blkbits
             // iomap->offset = 64512
         WARN_ON(iomap.offset > pos) // iomap.offset = 64512 and 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 bdev_add_partition().

Reported-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
Signed-off-by: Zhong Jinghua <zhongjinghua@xxxxxxxxxx>
---
 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