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References: <20221122143949.3493104-1-nfraprado@collabora.com>
In-Reply-To: <20221122143949.3493104-1-nfraprado@collabora.com>
From:   Chun-Kuang Hu <chunkuang.hu@kernel.org>
Date:   Fri, 27 Jan 2023 23:12:04 +0800
Message-ID: <CAAOTY__oFQ8DyAbdCyQEGAw7tFi+6AONiOHZxu_qJhT9MHNpoQ@mail.gmail.com>
Subject: Re: [PATCH v2] drm/mediatek: Clean dangling pointer on bind error path
To:     =?UTF-8?B?TsOtY29sYXMgRi4gUi4gQS4gUHJhZG8=?= 
        <nfraprado@collabora.com>
Cc:     Chun-Kuang Hu <chunkuang.hu@kernel.org>, kernel@collabora.com,
        "Nancy . Lin" <nancy.lin@mediatek.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        CK Hu <ck.hu@mediatek.com>,
        Daniel Kurtz <djkurtz@chromium.org>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@gmail.com>,
        Mao Huang <littlecvr@chromium.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        YT Shen <yt.shen@mediatek.com>,
        dri-devel@lists.freedesktop.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-mediatek@lists.infradead.org
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Hi, Nicolas:

N=C3=ADcolas F. R. A. Prado <nfraprado@collabora.com> =E6=96=BC 2022=E5=B9=
=B411=E6=9C=8822=E6=97=A5 =E9=80=B1=E4=BA=8C =E4=B8=8B=E5=8D=8810:39=E5=AF=
=AB=E9=81=93=EF=BC=9A
>
> mtk_drm_bind() can fail, in which case drm_dev_put() is called,
> destroying the drm_device object. However a pointer to it was still
> being held in the private object, and that pointer would be passed along
> to DRM in mtk_drm_sys_prepare() if a suspend were triggered at that
> point, resulting in a panic. Clean the pointer when destroying the
> object in the error path to prevent this from happening.

Applied to mediatek-drm-next [1], thanks.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/=
log/?h=3Dmediatek-drm-next

Regards,
Chun-Kuang.

>
> Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC MT817=
3.")
> Signed-off-by: N=C3=ADcolas F. R. A. Prado <nfraprado@collabora.com>
>
> ---
>
> Changes in v2:
> - Added Fixes tag
>
>  drivers/gpu/drm/mediatek/mtk_drm_drv.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/med=
iatek/mtk_drm_drv.c
> index 39a42dc8fb85..a21ff1b3258c 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> @@ -514,6 +514,7 @@ static int mtk_drm_bind(struct device *dev)
>  err_deinit:
>         mtk_drm_kms_deinit(drm);
>  err_free:
> +       private->drm =3D NULL;
>         drm_dev_put(drm);
>         return ret;
>  }
> --
> 2.38.1
>