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>
---
block/partition-generic.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/block/partition-generic.c b/block/partition-generic.c
index db57cced9b98..68bd04d044b9 100644
--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -270,6 +270,7 @@ 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;
@@ -283,6 +284,11 @@ void delete_partition(struct gendisk *disk, int partno)
kobject_put(part->holder_dir);
device_del(part_to_dev(part));
+ bdev = bdget(part_devt(part));
+ if (bdev) {
+ remove_inode_hash(bdev->bd_inode);
+ bdput(bdev);
+ }
hd_struct_kill(part);
}
--
2.38.1
