linux-kernel - Re: [PATCH v2] block: add check that partition length needs to be aligned with block size

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Date:   Tue, 27 Jun 2023 13:39:26 +0900
From:   Damien Le Moal <dlemoal@...nel.org>
To:     Min Li <min15.li@...sung.com>, axboe@...nel.dk,
        willy@...radead.org, hch@....de, gregkh@...uxfoundation.org
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] block: add check that partition length needs to be
 aligned with block size

On 6/27/23 20:09, Min Li wrote:
> Before calling add partition or resize partition, there is no check
> on whether the length is aligned with the logical block size.
> If the logical block size of the disk is larger than 512 bytes,
> then the partition size maybe not the multiple of the logical block size,
> and when the last sector is read, bio_truncate() will adjust the bio size,
> resulting in an IO error if the size of the read command is smaller than
> the logical block size.If integrity data is supported, this will also
> result in a null pointer dereference when calling bio_integrity_free.
> 
> Signed-off-by: Min Li <min15.li@...sung.com>

See Greg's comment: this likely need a "Fixes:" tag. And I think that the tag
is: fa9156ae597c ("block: refactor blkpg_ioctl"). But please double check.

> 
> ---
> Changes from v1:
> 
> - Add a space after /* and before */.
> - Move length alignment check before the "start = p.start >> SECTOR_SHIFT"
> - Move check for p.start being aligned together with this length alignment check.
> ---
>  block/ioctl.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/block/ioctl.c b/block/ioctl.c
> index 3be11941fb2d..c40b382dd58f 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -33,14 +33,18 @@ static int blkpg_do_ioctl(struct block_device *bdev,
>  	if (op == BLKPG_DEL_PARTITION)
>  		return bdev_del_partition(disk, p.pno);
>  
> +	/* check if partition is aligned to blocksize */
> +	if (p.start & (bdev_logical_block_size(bdev) - 1))
> +		return -EINVAL;
> +	/* check if length is aligned to blocksize */
> +	if (p.length & (bdev_logical_block_size(bdev) - 1))
> +		return -EINVAL;

	long long blksz_mask = bdev_logical_block_size(bdev) - 1;

	/* Check that the partition is aligned to the block size */
	if ((p.start & blksz_mask) || (p.length & blksz_mask))
		return -EINVAL;

would be cleaner and avoid the rather redundant comments.

> +
>  	start = p.start >> SECTOR_SHIFT;
>  	length = p.length >> SECTOR_SHIFT;
>  
>  	switch (op) {
>  	case BLKPG_ADD_PARTITION:
> -		/* check if partition is aligned to blocksize */
> -		if (p.start & (bdev_logical_block_size(bdev) - 1))
> -			return -EINVAL;
>  		return bdev_add_partition(disk, p.pno, start, length);
>  	case BLKPG_RESIZE_PARTITION:
>  		return bdev_resize_partition(disk, p.pno, start, length);

-- 
Damien Le Moal
Western Digital Research