linux-kernel - Re: [Nouveau] [PATCH] drm/nouveau/dispnv04: fix a possible null pointer dereference

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Date:   Mon, 23 Oct 2023 23:29:23 +0200
From:   Danilo Krummrich <dakr@...hat.com>
To:     Ma Ke <make_ruc2021@....com>, kherbst@...hat.com, lyude@...hat.com,
        dakr@...hat.com, airlied@...il.com, daniel@...ll.ch,
        tzimmermann@...e.de, noralf@...nnes.org, mripard@...nel.org,
        jani.nikula@...el.com
Cc:     nouveau@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [Nouveau] [PATCH] drm/nouveau/dispnv04: fix a possible null
 pointer dereference

On 10/13/23 03:18, Ma Ke wrote:
> In nv17_tv_get_hd_modes(), 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(). The same applies to drm_cvt_mode().
> Add a check to avoid null pointer dereference.
> 
> Signed-off-by: Ma Ke <make_ruc2021@....com>

For this one and the previous patch, please add the corresponding
'Fixes:' [1] and stable [2] tags and split the commits accordingly.

[1] https://www.kernel.org/doc/html/latest/process/submitting-patches.html#using-reported-by-tested-by-reviewed-by-suggested-by-and-fixes
[2] https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html

> ---
>   drivers/gpu/drm/nouveau/dispnv04/tvnv17.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/nouveau/dispnv04/tvnv17.c b/drivers/gpu/drm/nouveau/dispnv04/tvnv17.c
> index 670c9739e5e1..9c3dc9a5bb46 100644
> --- a/drivers/gpu/drm/nouveau/dispnv04/tvnv17.c
> +++ b/drivers/gpu/drm/nouveau/dispnv04/tvnv17.c
> @@ -258,6 +258,8 @@ static int nv17_tv_get_hd_modes(struct drm_encoder *encoder,
>   		if (modes[i].hdisplay == output_mode->hdisplay &&
>   		    modes[i].vdisplay == output_mode->vdisplay) {
>   			mode = drm_mode_duplicate(encoder->dev, output_mode);
> +			if (!mode)
> +				continue;
>   			mode->type |= DRM_MODE_TYPE_PREFERRED;
>   
>   		} else {
> @@ -265,6 +267,8 @@ static int nv17_tv_get_hd_modes(struct drm_encoder *encoder,
>   					    modes[i].vdisplay, 60, false,
>   					    (output_mode->flags &
>   					     DRM_MODE_FLAG_INTERLACE), false);
> +			if (!mode)
> +				continue;
>   		}
>   
>   		/* CVT modes are sometimes unsuitable... */