Re: [PATCH v2 2/2] btrfs: qgroup: add sysfs interface for debug

Chris Down
2020-07-15T13:49:36Z

Hi Wenruo,

While testing my pending patches on top of linux-next, I encountered a bug that
seems related to this patch during btrfs unmount. Specifically, a null pointer
dereference in kobject_del inside btrfs_sysfs_del_qgroups from close_ctree.

The fix may be as simple as checking if the kobject is initialised, although
perhaps it should always be initialised in this case, so I'll leave you to work
out what the real issue is :-)

RIP: kobject_del+0x1/0x20

[...]

Call Trace:
btrfs_sysfs_del_qgroups+0xa5/0xe0
close_ctree+0x1cd/0x2c0
generic_shutdown_super+0x6c/0x100
kill_anon_super+0x14/0x30
btrfs_kill_super+0x12/0x20
deactivate_locked_super+0x36/0x90
cleanup_mnt+0x12d/0x190
task_work_run+0x5c/0x90
__prepare_exit_to_usermode+0x164/0x170
[...]

Thanks,

Chris