linux-kernel - Re: [PATCH v4 05/45] drm/connector: Check drm_connector

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Message-ID: <87h6l66nth.fsf@intel.com>
Date:   Tue, 28 Nov 2023 14:54:02 +0200
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Maxime Ripard <mripard@...nel.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, Emma Anholt <emma@...olt.net>,
        Jonathan Corbet <corbet@....net>,
        Sandy Huang <hjc@...k-chips.com>,
        Heiko Stübner <heiko@...ech.de>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>
Cc:     Hans Verkuil <hverkuil@...all.nl>, dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        Maxime Ripard <mripard@...nel.org>
Subject: Re: [PATCH v4 05/45] drm/connector: Check drm_connector_init
 pointers arguments

On Tue, 28 Nov 2023, Maxime Ripard <mripard@...nel.org> wrote:
> All the drm_connector_init variants take at least a pointer to the
> device, connector and hooks implementation.
>
> However, none of them check their value before dereferencing those
> pointers which can lead to a NULL-pointer dereference if the author
> isn't careful.

Arguably oopsing on the spot is preferrable when this can't be caused by
user input. It's always a mistake that should be caught early during
development.

Not everyone checks the return value of drm_connector_init and friends,
so those cases will lead to more mysterious bugs later. And probably
oopses as well.


BR,
Jani.


>
> Let's test those pointers instead and error out if any is NULL.
>
> Signed-off-by: Maxime Ripard <mripard@...nel.org>
> ---
>  drivers/gpu/drm/drm_connector.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index b0516505f7ae..2f60755dccdd 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -229,6 +229,9 @@ static int __drm_connector_init(struct drm_device *dev,
>  	struct ida *connector_ida =
>  		&drm_connector_enum_list[connector_type].ida;
>  
> +	if (!dev || !connector || !funcs)
> +		return -EINVAL;
> +
>  	WARN_ON(drm_drv_uses_atomic_modeset(dev) &&
>  		(!funcs->atomic_destroy_state ||
>  		 !funcs->atomic_duplicate_state));

-- 
Jani Nikula, Intel