2023-05-25 07:36:03

by zhongjinghua

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

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 <[email protected]>
Signed-off-by: Zhong Jinghua <[email protected]>
---
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

2023-05-26 05:40:42

by Eric Biggers

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

On Thu, May 25, 2023 at 03:20:41PM +0800, Zhong Jinghua wrote:
> + if (p.start < 0 || p.length <= 0 || p.start + p.length < 0)
> + return -EINVAL;

Were zero-length partitions allowed before?

- Eric

2023-05-30 13:55:10

by zhongjinghua

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

在 2023/5/26 13:35, Eric Biggers 写道:
> On Thu, May 25, 2023 at 03:20:41PM +0800, Zhong Jinghua wrote:
>> + if (p.start < 0 || p.length <= 0 || p.start + p.length < 0)
>> + return -EINVAL;
> Were zero-length partitions allowed before?
Before this patch,  the io to the zero-length partition failed, I think
it is meaningless, and it was fixed by the way
> - Eric