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 08:19:23AM -0700, Jens Axboe wrote:
> On 12/5/22 8:08 AM, Greg Kroah-Hartman wrote:
> > 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.
> 
> Acked-by: Jens Axboe <axboe@kernel.dk>

Thanks, now queued up for 5.10.y

greg k-h