linux-kernel - Re: [PATCH v4] block: add check that partition length needs to be aligned with block size

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Date:   Thu, 29 Jun 2023 11:38:09 +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,
        stable@...r.kernel.org
Subject: Re: [PATCH v4] block: add check that partition length needs to be
 aligned with block size

On 6/29/23 19:26, 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.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Min Li <min15.li@...sung.com>>
> ---
> 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.
> 
> Changes from v2:
> 
> - Add the assignment on the first line and merge the two lines into one.
> 
> Changes from v3:
> 
> - Change the blksz to unsigned int.
> - Add check if p.start and p.length are negative.
> ---
>  block/ioctl.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/block/ioctl.c b/block/ioctl.c
> index 3be11941fb2d..a8061c2fcae0 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -16,9 +16,10 @@
>  static int blkpg_do_ioctl(struct block_device *bdev,
>  			  struct blkpg_partition __user *upart, int op)
>  {
> +	unsigned int blksz = bdev_logical_block_size(bdev);
>  	struct gendisk *disk = bdev->bd_disk;
>  	struct blkpg_partition p;
> -	long long start, length;
> +	sector_t start, length;
>  
>  	if (!capable(CAP_SYS_ADMIN))
>  		return -EACCES;
> @@ -33,14 +34,17 @@ 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;
> +	/* Check that the partition is aligned to the block size */
> +	if (!IS_ALIGNED(p.start | p.length, blksz))

Minor nit: blksz is used only here now, so this could be changed to:

	if (!IS_ALIGNED(p.start | p.length, bdev_logical_block_size(bdev)))

to not use that local variable.

With or without this addressed, looks good to me.

Reviewed-by: Damien Le Moal <dlemoal@...nel.org>

> +		return -EINVAL;
> +
>  	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