linux-kernel - Re: [PATCH 1/1] radeon: fix a possible null pointer dereference

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Date:   Tue, 17 May 2022 12:06:47 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Yuanjun Gong <ruc_gongyuanjun@....com>
Cc:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        amd-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 1/1] radeon: fix a possible null pointer dereference

On Tue, May 17, 2022 at 05:57:00PM +0800, Yuanjun Gong wrote:
> From: Gong Yuanjun <ruc_gongyuanjun@....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@....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
> 

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>