linux-kernel - Re: [PATCH] PM: domains: Ensure genpd_debugfs

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Date:   Tue, 5 Jul 2022 12:38:37 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Hsin-Yi Wang <hsinyi@...omium.org>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Thierry Strudel <tstrudel@...gle.com>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Pin-yen Lin <treapking@...omium.org>
Subject: Re: [PATCH] PM: domains: Ensure genpd_debugfs_dir exists before
 remove

On Tue, Jul 05, 2022 at 05:49:47PM +0800, Hsin-Yi Wang wrote:
> genpd_debug_remove() may be indirectly called from others while
> genpd_debugfs_dir is not yet set. Make sure genpd_debugfs_dir exists
> before remove the sub components, otherwise components under
> /sys/kernel/debug may be accidentally removed.
> 
> Fixes: 718072ceb211 ("PM: domains: create debugfs nodes when adding power domains")
> Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> ---
> An example:
> scpsys_probe() in drivers/soc/mediatek/mtk-pm-domains.c indirectly calls
> genpd_debug_remove() on probe fail, causing /sys/kernel/debug/usb to be
> removed.
> ---
>  drivers/base/power/domain.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 3e86772d5fac5..5a2e0232862e0 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -222,6 +222,9 @@ static void genpd_debug_remove(struct generic_pm_domain *genpd)
>  {
>  	struct dentry *d;
>  
> +	if (!genpd_debugfs_dir)
> +		return;
> +
>  	d = debugfs_lookup(genpd->name, genpd_debugfs_dir);
>  	debugfs_remove(d);

Why not just change this to be:
	debugfs_remove(debugfs_lookup(genpd->name, debugfs_lookup("pm_genpd", NULL)));

thanks,

greg k-h