Re: [PATCH v1] drm/modes: Skip invalid cmdline mode

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <maxime.ripard@bootlin.com>,
	Sean Paul <sean@poorly.run>, Daniel Vetter <daniel@ffwll.ch>,
	David Airlie <airlied@linux.ie>,
	linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org,
	dri-devel@lists.freedesktop.org
Subject: Re: [PATCH v1] drm/modes: Skip invalid cmdline mode
Date: Wed, 10 Jul 2019 13:00:00 +0300	[thread overview]
Message-ID: <20190710100000.GZ5942@intel.com> (raw)
In-Reply-To: <20190709145151.23086-1-digetx@gmail.com>

On Tue, Jul 09, 2019 at 05:51:51PM +0300, Dmitry Osipenko wrote:
> The named mode could be invalid and then cmdline parser misses to validate
> mode's dimensions, happily adding 0x0 mode as a valid mode. One case where
> this happens is NVIDIA Tegra devices that are using downstream bootloader
> which adds "video=tegrafb" to the kernel's cmdline and thus upstream Tegra
> DRM driver fails to probe because of the invalid mode.
> 
> Fixes: 3aeeb13d8996 ("drm/modes: Support modes names on the command line")

Is that actually true? This problem has been in the code since forever AFAICS.

> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  drivers/gpu/drm/drm_client_modeset.c | 3 ++-
>  drivers/gpu/drm/drm_modes.c          | 6 ++++++
>  2 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_client_modeset.c b/drivers/gpu/drm/drm_client_modeset.c
> index e95fceac8f8b..56d36779d213 100644
> --- a/drivers/gpu/drm/drm_client_modeset.c
> +++ b/drivers/gpu/drm/drm_client_modeset.c
> @@ -180,7 +180,8 @@ drm_connector_pick_cmdline_mode(struct drm_connector *connector)
>  
>  create_mode:
>  	mode = drm_mode_create_from_cmdline_mode(connector->dev, cmdline_mode);
> -	list_add(&mode->head, &connector->modes);
> +	if (mode)
> +		list_add(&mode->head, &connector->modes);

That's the same as what I did here
https://patchwork.freedesktop.org/patch/309223/?series=61781&rev=1

But I'd have to rebase that so let's just go with your patch.

>  
>  	return mode;
>  }
> diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
> index 910561d4f071..74a5739df506 100644
> --- a/drivers/gpu/drm/drm_modes.c
> +++ b/drivers/gpu/drm/drm_modes.c
> @@ -158,6 +158,9 @@ struct drm_display_mode *drm_cvt_mode(struct drm_device *dev, int hdisplay,
>  	int interlace;
>  	u64 tmp;
>  
> +	if (!hdisplay || !vdisplay)
> +		return NULL;
> +
>  	/* allocate the drm_display_mode structure. If failure, we will
>  	 * return directly
>  	 */
> @@ -392,6 +395,9 @@ drm_gtf_mode_complex(struct drm_device *dev, int hdisplay, int vdisplay,
>  	int hsync, hfront_porch, vodd_front_porch_lines;
>  	unsigned int tmp1, tmp2;
>  
> +	if (!hdisplay || !vdisplay)
> +		return NULL;
> +

These lgtm

Patch is
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

>  	drm_mode = drm_mode_create(dev);
>  	if (!drm_mode)
>  		return NULL;
> -- 
> 2.22.0
> 
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-- 
Ville Syrjälä
Intel