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.
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>
Acked-by: Jens Axboe <axboe@xxxxxxxxx>
---
block/partitions/core.c | 7 +++++++
1 file changed, 7 insertions(+)
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -329,6 +329,7 @@ void delete_partition(struct hd_struct *
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 *
* "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);
}
