[PATCH V2] block: not create too many partitions

[PATCH V2] block: not create too many partitions

[Ming Lei]

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.
-- 
2.29.2

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

[Jens Axboe]

On 3/27/21 1:13 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.

Applied, thanks for nailing this one down, Ming.

-- 
Jens Axboe

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

[Bart Van Assche]

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.