Re: [PATCH 2/2] sched/debug: fix dentry leak in update_sched_domain_debugfs

[Peter Zijlstra]

On Fri, Sep 02, 2022 at 02:31:07PM +0200, Greg Kroah-Hartman wrote:
> Kuyo reports that the pattern of using debugfs_remove(debugfs_lookup())
> leaks a dentry and with a hotplug stress test, the machine eventually
> runs out of memory.
> 
> Fix this up by using the newly created debugfs_lookup_and_remove() call
> instead which properly handles the dentry reference counting logic.

> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

> ---
>  kernel/sched/debug.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> index bb3d63bdf4ae..667876da8382 100644
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> @@ -416,7 +416,7 @@ void update_sched_domain_debugfs(void)
>  		char buf[32];
>  
>  		snprintf(buf, sizeof(buf), "cpu%d", cpu);
> -		debugfs_remove(debugfs_lookup(buf, sd_dentry));
> +		debugfs_lookup_and_remove(buf, sd_dentry);
>  		d_cpu = debugfs_create_dir(buf, sd_dentry);
>  
>  		i = 0;
> -- 
> 2.37.3
>