linux-kernel - Re: [PATCH] drm/nouveau/dispnv04: fix null pointer dereference in nv17_tv_get_hd

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Date: Tue, 25 Jun 2024 15:11:41 -0400
From: Lyude Paul <lyude@...hat.com>
To: Ma Ke <make24@...as.ac.cn>, kherbst@...hat.com, dakr@...hat.com, 
	airlied@...il.com, daniel@...ll.ch
Cc: dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] drm/nouveau/dispnv04: fix null pointer dereference in
 nv17_tv_get_hd_modes

Reviewed-by: Lyude Paul <lyude@...hat.com>

I will push this and the other patch that you sent upstream in just a
moment, thanks!

On Tue, 2024-06-25 at 16:10 +0800, 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 possible NULL pointer
> dereference
> on failure of drm_mode_duplicate(). The same applies to
> drm_cvt_mode().
> Add a check to avoid null pointer dereference.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Ma Ke <make24@...as.ac.cn>
> ---
>  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... */

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat