[PATCH] block: always remove partitions from blk_drop_partitions()

[PATCH] block: always remove partitions from blk_drop_partitions()

[Ming Lei]

In theory, when GENHD_FL_NO_PART_SCAN is set, no partitions can be created
on one disk. However, ioctl(BLKPG, BLKPG_ADD_PARTITION) doesn't check
GENHD_FL_NO_PART_SCAN, so partitions still can be added even though
GENHD_FL_NO_PART_SCAN is set.

So far blk_drop_partitions() only removes partitions when disk_part_scan_enabled()
return true. This way can make ghost partition on loop device after changing/clearing
FD in case that PARTSCAN is disabled, such as partitions can be added
via 'parted' on loop disk even though GENHD_FL_NO_PART_SCAN is set.

Fix this issue by always removing partitions in blk_drop_partitions(), and
this way is correct because the current code supposes that no partitions
can be added in case of GENHD_FL_NO_PART_SCAN.

Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/partitions/core.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/block/partitions/core.c b/block/partitions/core.c
index 78951e33b2d7..e62a98a8eeb7 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -619,8 +619,6 @@ int blk_drop_partitions(struct block_device *bdev)
 	struct disk_part_iter piter;
 	struct hd_struct *part;
 
-	if (!disk_part_scan_enabled(bdev->bd_disk))
-		return 0;
 	if (bdev->bd_part_count)
 		return -EBUSY;
 
-- 
2.25.2

Re: [PATCH] block: always remove partitions from blk_drop_partitions()

[Christoph Hellwig]

On Wed, Jul 15, 2020 at 04:36:19PM +0800, Ming Lei wrote:
> In theory, when GENHD_FL_NO_PART_SCAN is set, no partitions can be created
> on one disk. However, ioctl(BLKPG, BLKPG_ADD_PARTITION) doesn't check
> GENHD_FL_NO_PART_SCAN, so partitions still can be added even though
> GENHD_FL_NO_PART_SCAN is set.
> 
> So far blk_drop_partitions() only removes partitions when disk_part_scan_enabled()
> return true. This way can make ghost partition on loop device after changing/clearing
> FD in case that PARTSCAN is disabled, such as partitions can be added
> via 'parted' on loop disk even though GENHD_FL_NO_PART_SCAN is set.
> 
> Fix this issue by always removing partitions in blk_drop_partitions(), and
> this way is correct because the current code supposes that no partitions
> can be added in case of GENHD_FL_NO_PART_SCAN.

The changelog has a few overly long lines.

Otherwise:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH] block: always remove partitions from blk_drop_partitions()

[Jens Axboe]

On 7/15/20 2:36 AM, Ming Lei wrote:
> In theory, when GENHD_FL_NO_PART_SCAN is set, no partitions can be created
> on one disk. However, ioctl(BLKPG, BLKPG_ADD_PARTITION) doesn't check
> GENHD_FL_NO_PART_SCAN, so partitions still can be added even though
> GENHD_FL_NO_PART_SCAN is set.
> 
> So far blk_drop_partitions() only removes partitions when disk_part_scan_enabled()
> return true. This way can make ghost partition on loop device after changing/clearing
> FD in case that PARTSCAN is disabled, such as partitions can be added
> via 'parted' on loop disk even though GENHD_FL_NO_PART_SCAN is set.
> 
> Fix this issue by always removing partitions in blk_drop_partitions(), and
> this way is correct because the current code supposes that no partitions
> can be added in case of GENHD_FL_NO_PART_SCAN.

Applied, thanks.

-- 
Jens Axboe