Re: [PATCH v2 2/3] block: don't delete queue kobject before its children

Greg Kroah-Hartman
2021-11-30T07:09:58Z

On Mon, Nov 29, 2021 at 08:03:05PM -0800, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> kobjects aren't supposed to be deleted before their child kobjects are
> deleted. Apparently this is usually benign; however, a WARN will be
> triggered if one of the child kobjects has a named attribute group:
>
> sysfs group 'modes' not found for kobject 'crypto'
> WARNING: CPU: 0 PID: 1 at fs/sysfs/group.c:278 sysfs_remove_group+0x72/0x80
> ...
> Call Trace:
> sysfs_remove_groups+0x29/0x40 fs/sysfs/group.c:312
> __kobject_del+0x20/0x80 lib/kobject.c:611
> kobject_cleanup+0xa4/0x140 lib/kobject.c:696
> kobject_release lib/kobject.c:736 [inline]
> kref_put include/linux/kref.h:65 [inline]
> kobject_put+0x53/0x70 lib/kobject.c:753
> blk_crypto_sysfs_unregister+0x10/0x20 block/blk-crypto-sysfs.c:159
> blk_unregister_queue+0xb0/0x110 block/blk-sysfs.c:962
> del_gendisk+0x117/0x250 block/genhd.c:610
>
> Fix this by moving the kobject_del() and the corresponding
> kobject_uevent() to the correct place.
>
> Fixes: 2c2086afc2b8 ("block: Protect less code with sysfs_lock in blk_{un,}register_queue()")
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
> block/blk-sysfs.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index 91d3805a6ec6b..1368dfe3ee500 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -951,15 +951,17 @@ void blk_unregister_queue(struct gendisk *disk)
> */
> if (queue_is_mq(q))
> blk_mq_unregister_dev(disk_to_dev(disk), q);
> -
> - kobject_uevent(&q->kobj, KOBJ_REMOVE);
> - kobject_del(&q->kobj);
> blk_trace_remove_sysfs(disk_to_dev(disk));
>
> mutex_lock(&q->sysfs_lock);
> elv_unregister_queue(q);
> disk_unregister_independent_access_ranges(disk);
> mutex_unlock(&q->sysfs_lock);
> +
> + /* Now that all child objects were deleted, the queue can be deleted. */
> + kobject_uevent(&q->kobj, KOBJ_REMOVE);
> + kobject_del(&q->kobj);
> +
> mutex_unlock(&q->sysfs_dir_lock);
>
> kobject_put(&disk_to_dev(disk)->kobj);
> --
> 2.34.1
>

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>