Re: [PATCH 5.10.y stable v2] block: unhash blkdev part inode when the part is deleted

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Mon, Dec 05, 2022 at 09:27:39PM +0800, Ming Lei wrote:
> v5.11 changes the blkdev lookup mechanism completely since commit
> 22ae8ce8b892 ("block: simplify bdev/disk lookup in blkdev_get"),
> and small part of the change is to unhash part bdev inode when
> deleting partition. Turns out this kind of change does fix one
> nasty issue in case of BLOCK_EXT_MAJOR:
> 
> 1) when one partition is deleted & closed, disk_put_part() is always
> called before bdput(bdev), see blkdev_put(); so the part's devt can
> be freed & re-used before the inode is dropped
> 
> 2) then new partition with same devt can be created just before the
> inode in 1) is dropped, then the old inode/bdev structurein 1) is
> re-used for this new partition, this way causes use-after-free and
> kernel panic.
> 
> It isn't possible to backport the whole big patchset of "merge struct
> block_device and struct hd_struct v4" for addressing this issue.
> 
> https://lore.kernel.org/linux-block/20201128161510.347752-1-hch@lst.de/
> 
> So fixes it by unhashing part bdev in delete_partition(), and this way
> is actually aligned with v5.11+'s behavior.
> 
> Reported-by: Shiwei Cui <cuishw@inspur.com>
> Tested-by: Shiwei Cui <cuishw@inspur.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Jan Kara <jack@suse.cz>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> V2:
> 	- fix one typo and Shiwei's email format
> 
>  block/partitions/core.c | 7 +++++++

I need an ack from the block maintainers/developers to be able to take
this.

thanks,

greg k-h