linux-kernel - Re: [PATCH -next] block: Fix the partition start may overflow in add

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Date:   Thu, 25 May 2023 10:14:33 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     Zhong Jinghua <zhongjinghua@...weicloud.com>, axboe@...nel.dk
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        zhongjinghua@...wei.com, yi.zhang@...wei.com,
        chengzhihao1@...wei.com, yangerkun@...wei.com,
        "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH -next] block: Fix the partition start may overflow in
 add_partition()

Hi,

在 2023/05/22 15:06, Zhong Jinghua 写道:
> From: Zhong Jinghua <zhongjinghua@...wei.com>
> 
> 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

start_sect is 0x8..... >> SECTOR_SHIFT.

> 
> 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().

The checking that you add is blkpg_do_ioctl().

> 
> Reported-by: Zhihao Cheng <chengzhihao1@...wei.com>
> Signed-off-by: Zhong Jinghua <zhongjinghua@...wei.com>
> ---
>   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 */
> 

The change itself looks good to me, feel free to add:

Reviewed-by: Yu Kuai <yukuai3@...wei.com>