linux-kernel - Re: [PATCH] drm/vc4: fix ref count leak in vc4_dsi_encoder

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Message-ID: <CAEkB2ESj-SgM9aSHdMp_wx_gUETO-CoD4jkR+nr_CLZRShrp5g@mail.gmail.com>
Date:   Sun, 14 Jun 2020 14:15:07 -0500
From:   Navid Emamdoost <navid.emamdoost@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Eric Anholt <eric@...olt.net>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Navid Emamdoost <emamd001@....edu>,
        Qiushi Wu <wu000273@....edu>, Kangjie Lu <kjlu@....edu>,
        Stephen McCamant <smccaman@....edu>
Subject: Re: [PATCH] drm/vc4: fix ref count leak in vc4_dsi_encoder_enable

On Sun, Jun 14, 2020 at 7:32 AM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> On Sun, Jun 14, 2020 at 9:55 AM Navid Emamdoost
> <navid.emamdoost@...il.com> wrote:
> >
> > in vc4_dsi_encoder_enable, the call to pm_runtime_get_sync increments
> > the counter even in case of failure, leading to incorrect
> > ref count. In case of failure, decrement the ref count before returning.
>
> ...
>
> > +out:
> > +       pm_runtime_put(dev);
>
> Better to use pm_runtime_put_noidle() for error case.
> And here is a change of semantics, i.e. before your patch there was no
> put at all. How did you test this?
I had no way to test this but looked to me like a miscalculation of
ref count when there is a get and an error happens then the ref count
should be restored. Does that look incorrect?

>
> --
> With Best Regards,
> Andy Shevchenko



-- 
Navid.