linux-kernel - Re: [PATCH v3] drm/rockchip: Refactor the component match logic.

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Message-ID: <2110531.OeyX13mlk5@phil>
Date:   Wed, 15 Mar 2017 18:23:27 +0100
From:   Heiko Stuebner <heiko@...ech.de>
To:     Jeffy Chen <jeffy.chen@...k-chips.com>
Cc:     Mark Yao <mark.yao@...k-chips.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Guenter Roeck <groeck@...omium.org>,
        Brian Norris <briannorris@...omium.org>,
        Tomasz Figa <tfiga@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Sean Paul <seanpaul@...omium.org>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-rockchip@...ts.infradead.org,
        David Airlie <airlied@...ux.ie>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3] drm/rockchip: Refactor the component match logic.

Am Mittwoch, 15. März 2017, 18:00:04 CET schrieb Heiko Stuebner:
> Am Mittwoch, 15. März 2017, 18:20:47 CET schrieb Jeffy Chen:
> > Currently we are adding all components from the dts, if one of their
> > drivers been disabled, we would not be able to bring up others.
> > 
> > Refactor component match logic, follow exynos drm.
> > 
> > Signed-off-by: Jeffy Chen <jeffy.chen@...k-chips.com>
> > Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>
> 
> This reliably produces null pointer dereference errors in
> 	__platform_driver_register called from rockchip_drm_init
> on at least rk3036 and rk3288 (probably more) when applied on top of
> Linus' tree from today. Log attached and Rockchip drm compiled as module.
> 
> I'm currently dug into other areas, so hadn't have time to investigate
> further yet.

> +#define DRV_PTR(drv, cond) (IS_ENABLED(cond) ? &drv : NULL)
> +
> +static struct platform_driver *rockchip_drm_comp_drvs[] = {
> +	&vop_platform_driver,
> +	DRV_PTR(rockchip_dp_driver, CONFIG_ROCKCHIP_ANALOGIX_DP),
> +	DRV_PTR(cdn_dp_driver, CONFIG_ROCKCHIP_CDN_DP),
> +	DRV_PTR(dw_hdmi_rockchip_pltfm_driver, CONFIG_ROCKCHIP_DW_HDMI),
> +	DRV_PTR(dw_mipi_dsi_driver, CONFIG_ROCKCHIP_DW_MIPI_DSI),
> +	DRV_PTR(inno_hdmi_driver, CONFIG_ROCKCHIP_INNO_HDMI),
> +};

[...]

> +static int rockchip_drm_register_drivers(void)
> +{
> +	int i, ret;
> +
> +	for (i = 0; i < ARRAY_SIZE(rockchip_drm_comp_drvs); i++) {
> +		ret = platform_driver_register(rockchip_drm_comp_drvs[i]);
> +		if (ret)
> +			goto err_unreg;
> +	}

This of course won't work in the NULL case, as platform_driver_register always 
dereferences its parameter [0], so you should only call it for the actual non-
null array elements - of course same for unregister.


Heiko

[0] http://lxr.free-electrons.com/source/drivers/base/platform.c#L617