From: Ming Lei <ming.lei@xxxxxxxxxx> 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@xxxxxx/ 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@xxxxxxxxxx> Tested-by: Shiwei Cui <cuishw@xxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: Jan Kara <jack@xxxxxxx> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- block/partition-generic.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/block/partition-generic.c +++ b/block/partition-generic.c @@ -272,6 +272,7 @@ void delete_partition(struct gendisk *di 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 *di * "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); }