linux-kernel - Re: [PATCH v4 1/2] drm/mediatek: fix kernel oops if no crtc is found

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Message-ID: <CAAOTY_9xrt_ku-fZotJAnPa2ns-2PCGken4TepMrQYG9KEJcFA@mail.gmail.com>
Date:   Fri, 8 Dec 2023 07:54:00 +0800
From:   Chun-Kuang Hu <chunkuang.hu@...nel.org>
To:     Michael Walle <mwalle@...nel.org>
Cc:     Nícolas F . R . A . Prado 
        <nfraprado@...labora.com>, Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        "Nancy . Lin" <nancy.lin@...iatek.com>,
        Frank Wunderlich <frank-w@...lic-files.de>,
        Jitao Shi <jitao.shi@...iatek.com>,
        Stu Hsieh <stu.hsieh@...iatek.com>,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 1/2] drm/mediatek: fix kernel oops if no crtc is found

Hi, Michael:

Michael Walle <mwalle@...nel.org> 於 2023年9月5日 週二 下午4:49寫道：
>
> drm_crtc_from_index(0) might return NULL if there are no CRTCs
> registered at all which will lead to a kernel oops in
> mtk_drm_crtc_dma_dev_get(). Add the missing return value check.

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

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

Regards,
Chun-Kuang.

>
> Fixes: 0d9eee9118b7 ("drm/mediatek: Add drm ovl_adaptor sub driver for MT8195")
> Signed-off-by: Michael Walle <mwalle@...nel.org>
> Reviewed-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
> Tested-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> ---
> v4:
>  - collected tags
> v3:
>  - none
> v2:
>  - collected tags
>  - fixed typos
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_drv.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> index 93552d76b6e7..2c582498817e 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> @@ -420,6 +420,7 @@ static int mtk_drm_kms_init(struct drm_device *drm)
>         struct mtk_drm_private *private = drm->dev_private;
>         struct mtk_drm_private *priv_n;
>         struct device *dma_dev = NULL;
> +       struct drm_crtc *crtc;
>         int ret, i, j;
>
>         if (drm_firmware_drivers_only())
> @@ -494,7 +495,9 @@ static int mtk_drm_kms_init(struct drm_device *drm)
>         }
>
>         /* Use OVL device for all DMA memory allocations */
> -       dma_dev = mtk_drm_crtc_dma_dev_get(drm_crtc_from_index(drm, 0));
> +       crtc = drm_crtc_from_index(drm, 0);
> +       if (crtc)
> +               dma_dev = mtk_drm_crtc_dma_dev_get(crtc);
>         if (!dma_dev) {
>                 ret = -ENODEV;
>                 dev_err(drm->dev, "Need at least one OVL device\n");
> --
> 2.39.2
>