[PATCH stable 5.4.y/4.19.y] block: unhash blkdev part inode when the part is deleted

[PATCH stable 5.4.y/4.19.y] 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.

Backported from the following 5.10.y commit:

5f2f77560591 ("block: unhash blkdev part inode when the part is deleted")

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>
---
 block/partition-generic.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/block/partition-generic.c b/block/partition-generic.c
index aee643ce13d1..e69452c1f5ad 100644
--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -272,6 +272,7 @@ void delete_partition(struct gendisk *disk, int partno)
 	struct disk_part_tbl *ptbl =
 		rcu_dereference_protected(disk->part_tbl, 1);
 	struct hd_struct *part;
+	struct block_device *bdev;
 
 	if (partno >= ptbl->len)
 		return;
@@ -292,6 +293,12 @@ void delete_partition(struct gendisk *disk, int partno)
 	 * "in-use" until we really free the gendisk.
 	 */
 	blk_invalidate_devt(part_devt(part));
+
+	bdev = bdget(part_devt(part));
+	if (bdev) {
+		remove_inode_hash(bdev->bd_inode);
+		bdput(bdev);
+	}
 	hd_struct_kill(part);
 }
 
-- 
2.38.1

Re: [PATCH stable 5.4.y/4.19.y] 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 stable 5.4.y/4.19.y] block: unhash blkdev part inode when the part is deleted
Link: https://lore.kernel.org/stable/20221213071603.1197703-1-ming.lei%40redhat.com

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

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https://01.org/lkp