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

[PATCH 5.10.y stable v2] 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 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 +++++++
 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 v2] 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 v2] block: unhash blkdev part inode when the part is deleted
Link: https://lore.kernel.org/stable/20221205132739.844399-1-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 v2] block: unhash blkdev part inode when the part is deleted

[Greg Kroah-Hartman]

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

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

[Jens Axboe]

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>

-- 
Jens Axboe

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

[Greg Kroah-Hartman]

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