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

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

[Ming Lei]

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
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
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/partitions/core.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/block/partitions/core.c b/block/partitions/core.c
index a02e22411594..e3d61ec4a5a6 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -329,6 +329,7 @@ void delete_partition(struct hd_struct *part)
 	struct gendisk *disk = part_to_disk(part);
 	struct disk_part_tbl *ptbl =
 		rcu_dereference_protected(disk->part_tbl, 1);
+	struct block_device *bdev;
 
 	/*
 	 * ->part_tbl is referenced in this part's release handler, so
@@ -346,6 +347,12 @@ void delete_partition(struct hd_struct *part)
 	 * "in-use" until we really free the gendisk.
 	 */
 	blk_invalidate_devt(part_devt(part));
+
+	bdev = bdget_part(part);
+	if (bdev) {
+		remove_inode_hash(bdev->bd_inode);
+		bdput(bdev);
+	}
 	percpu_ref_kill(&part->ref);
 }
 
-- 
2.37.3

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

[kernel test robot]

Hi,

Thanks for your patch.

FYI: kernel test robot notices the stable kernel rule is not satisfied.

Rule: 'Cc: stable@vger.kernel.org' or 'commit <sha1> upstream.'
Subject: [PATCH 5.10.y stable] block: unhash blkdev part inode when the part is deleted
Link: https://lore.kernel.org/stable/20221205122502.841896-1-ming.lei%40redhat.com

The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

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

[Greg Kroah-Hartman]

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"?

> 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 (<>)

> 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?

thanks,

greg k-h

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

[Ming Lei]

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