Re: [PATCH V2] block: not create too many partitions

[Bart Van Assche <bvanassche@acm.org>]

On 3/27/21 12:13 AM, Ming Lei wrote:
> Commit a33df75c6328 ("block: use an xarray for disk->part_tbl") drops
> check on max supported partitions number, and allows partition with
> bigger partition number to be added. However, ->bd_partno is defined
> as u8, so partition index of xarray table may not match with ->bd_partno.
> Then delete_partition() may delete one unmatched partition, and caused
> use-after-free.
> 
> Cc: Bart Van Assche <bvanassche@acm.org>
> Reported-by: syzbot+8fede7e30c7cee0de139@syzkaller.appspotmail.com
> Fixes: a33df75c6328 ("block: use an xarray for disk->part_tbl")
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> V2:
> 	- don't check disk_max_parts() which is supposed to not zero
> 
>  block/partitions/core.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/block/partitions/core.c b/block/partitions/core.c
> index 1a7558917c47..46f055bc7ecb 100644
> --- a/block/partitions/core.c
> +++ b/block/partitions/core.c
> @@ -322,6 +322,13 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
>  	const char *dname;
>  	int err;
>  
> +	/*
> +	 * disk_max_parts() won't be zero, either GENHD_FL_EXT_DEVT is set
> +	 * or 'minors' is passed to alloc_disk().
> +	 */
> +	if (partno >= disk_max_parts(disk))
> +		return ERR_PTR(-EINVAL);
> +
>  	/*
>  	 * Partitions are not supported on zoned block devices that are used as
>  	 * such.
> 

Reviewed-by: Bart Van Assche <bvanassche@acm.org>

Thanks!

Bart.