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

Ming Lei
2022-12-05T13:17:36Z

On Mon, Dec 05, 2022 at 01:33:32PM +0100, Greg Kroah-Hartman wrote:
> On Mon, Dec 05, 2022 at 08:25:02PM +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 fbig patchset of "merge struct
>
> "fbig"?

OK, will fix it in v2.

>
> > 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: cuishw@inspur.com
> > Tested-by: cuishw@inspur.com
>
> We need a real name and this in a proper format as well (<>)

cuishw, care to share us your name? :-)

>
> > Cc: Christoph Hellwig <hch@lst.de>
> > Cc: Jan Kara <jack@suse.cz>
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
>
> What about for kernels older than 5.10?

All -stable kernels older should need this kind of fix. If this
patch is acked, I can backport to other -stable kernels.

Thanks,
Ming