Re: [PATCH] fs/kernfs: Fix lockdep warning in kernfs_active()

[Tejun Heo]

On Wed, Nov 09, 2022 at 08:04:15PM +0800, Chengming Zhou wrote:
> syzbot found a lockdep warning in kernfs_find_and_get_node_by_id(),
> bisected to the commit c25491747b21 ("kernfs: Add KERNFS_REMOVING flags"),
> which didn't hold kernfs_rwsem before call kernfs_active(kn).
> 
> Since kernfs_find_and_get_node_by_id() doesn't have to get active count
> of kn, only need to get a stable refcount of kn, so it should be enough
> to just check kn has been KERNFS_ACTIVATED.
> 
> Reported-by: syzbot+2fdf66e68f5f882c1074@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: c25491747b21 ("kernfs: Add KERNFS_REMOVING flags")
> Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>

Acked-by: Tejun Heo <tj@xxxxxxxxxx>

Thanks.

-- 
tejun