linux-kernel - Re: [PATCH 2/2] sched/debug: fix dentry leak in update_sched_domain

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Message-ID: <YxH7NIe0Inz2V6sH@kroah.com>
Date:   Fri, 2 Sep 2022 14:46:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Major Chen <major.chen@...sung.com>, stable <stable@...nel.org>,
        Kuyo Chang <kuyo.chang@...iatek.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Matthias Brugger <matthias.bgg@...il.com>
Subject: Re: [PATCH 2/2] sched/debug: fix dentry leak in
 update_sched_domain_debugfs

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.
> 
> Cc: Major Chen <major.chen@...sung.com>
> Cc: stable <stable@...nel.org>
> Reported-by: Kuyo Chang <kuyo.chang@...iatek.com>
> Tested-by: Kuyo Chang <kuyo.chang@...iatek.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Juri Lelli <juri.lelli@...hat.com>
> Cc: Vincent Guittot <vincent.guittot@...aro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@....com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Ben Segall <bsegall@...gle.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
> Cc: Valentin Schneider <vschneid@...hat.com>
> Cc: Matthias Brugger <matthias.bgg@...il.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>  kernel/sched/debug.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

As this needs patch 1/2 to work properly, and Kuyo has tested this out
already, I'll take both of them through my driver core git tree to Linus
so that we can start getting the other debugfs_lookup() leaks fixed up
as well.

thanks,

greg k-h