linux-kernel - Re: [PATCH 2/2] drm/meson: encoder_hdmi: Fix refcount leak in meson_encoder_hdmi

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Message-ID: <CAFBinCANaU4Tk42j-GDBWwUDk39_XiCfeu4D9vGFjFc_G4PZGQ@mail.gmail.com>
Date:   Tue, 31 May 2022 22:03:23 +0200
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Miaoqian Lin <linmq006@...il.com>
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Sam Ravnborg <sam@...nborg.org>,
        dri-devel@...ts.freedesktop.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] drm/meson: encoder_hdmi: Fix refcount leak in meson_encoder_hdmi_init

Hello,

first of all: thank you for spotting this and sending a patch!

On Tue, May 31, 2022 at 4:49 PM Miaoqian Lin <linmq006@...il.com> wrote:
[...]
> diff --git a/drivers/gpu/drm/meson/meson_encoder_hdmi.c b/drivers/gpu/drm/meson/meson_encoder_hdmi.c
> index 5e306de6f485..f3341458f8b7 100644
> --- a/drivers/gpu/drm/meson/meson_encoder_hdmi.c
> +++ b/drivers/gpu/drm/meson/meson_encoder_hdmi.c
> @@ -363,6 +363,7 @@ int meson_encoder_hdmi_init(struct meson_drm *priv)
>         }
>
>         meson_encoder_hdmi->next_bridge = of_drm_find_bridge(remote);
> +       of_node_put(remote);
further down in the same function remote is used again:
  pdev = of_find_device_by_node(remote);

My understanding is that we should only use of_node_put() once we
don't need to access the node (in this case the variable is "remote")
anymore.


Best regards,
Martin