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); }