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From:   Alex Deucher <alexdeucher@gmail.com>
Date:   Tue, 17 May 2022 16:54:11 -0400
Message-ID: <CADnq5_MM7pV-yXRdqRsqoWOugOF8SjXgvksXWoot5W+VkLeAGw@mail.gmail.com>
Subject: Re: [PATCH 1/1] radeon: fix a possible null pointer dereference
To:     Yuanjun Gong <ruc_gongyuanjun@163.com>
Cc:     Alex Deucher <alexander.deucher@amd.com>,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
        amd-gfx list <amd-gfx@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>
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Applied.  Thanks!

On Tue, May 17, 2022 at 9:13 AM Yuanjun Gong <ruc_gongyuanjun@163.com> wrote:
>
> From: Gong Yuanjun <ruc_gongyuanjun@163.com>
>
> In radeon_fp_native_mode(), the return value of drm_mode_duplicate()
> is assigned to mode, which will lead to a NULL pointer dereference
> on failure of drm_mode_duplicate(). Add a check to avoid npd.
>
> The failure status of drm_cvt_mode() on the other path is checked too.
>
> Signed-off-by: Gong Yuanjun <ruc_gongyuanjun@163.com>
> ---
>  drivers/gpu/drm/radeon/radeon_connectors.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c
> index 0cb1345c6ba4..fabe4f4ca124 100644
> --- a/drivers/gpu/drm/radeon/radeon_connectors.c
> +++ b/drivers/gpu/drm/radeon/radeon_connectors.c
> @@ -473,6 +473,8 @@ static struct drm_display_mode *radeon_fp_native_mode(struct drm_encoder *encode
>             native_mode->vdisplay != 0 &&
>             native_mode->clock != 0) {
>                 mode = drm_mode_duplicate(dev, native_mode);
> +               if (!mode)
> +                       return NULL;
>                 mode->type = DRM_MODE_TYPE_PREFERRED | DRM_MODE_TYPE_DRIVER;
>                 drm_mode_set_name(mode);
>
> @@ -487,6 +489,8 @@ static struct drm_display_mode *radeon_fp_native_mode(struct drm_encoder *encode
>                  * simpler.
>                  */
>                 mode = drm_cvt_mode(dev, native_mode->hdisplay, native_mode->vdisplay, 60, true, false, false);
> +               if (!mode)
> +                       return NULL;
>                 mode->type = DRM_MODE_TYPE_PREFERRED | DRM_MODE_TYPE_DRIVER;
>                 DRM_DEBUG_KMS("Adding cvt approximation of native panel mode %s\n", mode->name);
>         }
> --
> 2.17.1
>