Re: [PATCH] Revert "drm/imx: don't destroy mode objects manually on driver unbind"

[Daniel Vetter]

On Tue, Oct 16, 2018 at 06:09:23PM +0200, Stefan Agner wrote:
> This reverts commit 8e3b16e2117409625b89807de3912ff773aea354.
> 
> Using the component framework requires all components to undo in
> ->unbind what ->bind does. Unfortunately that particular commit
> broke this rule. In particular, this is an issue if a single
> component during probe fails. In that case, component_bind_all()
> calls unbind on already succussfully bound components, and then
> frees memory allocated using devm. If one of those components
> registered e.g. an encoder with the framework then this leads to
> use after free situations.
> 
> Revert the commit to ensure that all components properly undo
> what ->bind does.
> 
> Link: https://www.mail-archive.com/dri-devel@xxxxxxxxxxxxxxxxxxxxx/msg233327.html
> Suggested-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
> Signed-off-by: Stefan Agner <stefan@xxxxxxxx>

Adding Benjamin, who just made the same mistake I think (and I reviewed it
... oh well).
-Daniel

> ---
>  drivers/gpu/drm/imx/imx-drm-core.c     | 4 ++--
>  drivers/gpu/drm/imx/imx-ldb.c          | 6 ++++++
>  drivers/gpu/drm/imx/imx-tve.c          | 3 +++
>  drivers/gpu/drm/imx/parallel-display.c | 3 +++
>  4 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/imx/imx-drm-core.c b/drivers/gpu/drm/imx/imx-drm-core.c
> index 5ea0c82f9957..caa6061a98ba 100644
> --- a/drivers/gpu/drm/imx/imx-drm-core.c
> +++ b/drivers/gpu/drm/imx/imx-drm-core.c
> @@ -305,11 +305,11 @@ static void imx_drm_unbind(struct device *dev)
>  
>  	drm_fb_cma_fbdev_fini(drm);
>  
> -	drm_mode_config_cleanup(drm);
> -
>  	component_unbind_all(drm->dev, drm);
>  	dev_set_drvdata(dev, NULL);
>  
> +	drm_mode_config_cleanup(drm);
> +
>  	drm_dev_put(drm);
>  }
>  
> diff --git a/drivers/gpu/drm/imx/imx-ldb.c b/drivers/gpu/drm/imx/imx-ldb.c
> index 3bd0f8a18e74..592aabc4a262 100644
> --- a/drivers/gpu/drm/imx/imx-ldb.c
> +++ b/drivers/gpu/drm/imx/imx-ldb.c
> @@ -723,6 +723,12 @@ static void imx_ldb_unbind(struct device *dev, struct device *master,
>  		if (channel->panel)
>  			drm_panel_detach(channel->panel);
>  
> +		if (!channel->connector.funcs)
> +			continue;
> +
> +		channel->connector.funcs->destroy(&channel->connector);
> +		channel->encoder.funcs->destroy(&channel->encoder);
> +
>  		kfree(channel->edid);
>  		i2c_put_adapter(channel->ddc);
>  	}
> diff --git a/drivers/gpu/drm/imx/imx-tve.c b/drivers/gpu/drm/imx/imx-tve.c
> index cffd3310240e..8d6e89ce1edb 100644
> --- a/drivers/gpu/drm/imx/imx-tve.c
> +++ b/drivers/gpu/drm/imx/imx-tve.c
> @@ -673,6 +673,9 @@ static void imx_tve_unbind(struct device *dev, struct device *master,
>  {
>  	struct imx_tve *tve = dev_get_drvdata(dev);
>  
> +	tve->connector.funcs->destroy(&tve->connector);
> +	tve->encoder.funcs->destroy(&tve->encoder);
> +
>  	if (!IS_ERR(tve->dac_reg))
>  		regulator_disable(tve->dac_reg);
>  }
> diff --git a/drivers/gpu/drm/imx/parallel-display.c b/drivers/gpu/drm/imx/parallel-display.c
> index aefd04e18f93..6f11bffcde37 100644
> --- a/drivers/gpu/drm/imx/parallel-display.c
> +++ b/drivers/gpu/drm/imx/parallel-display.c
> @@ -258,6 +258,9 @@ static void imx_pd_unbind(struct device *dev, struct device *master,
>  	if (imxpd->panel)
>  		drm_panel_detach(imxpd->panel);
>  
> +	imxpd->encoder.funcs->destroy(&imxpd->encoder);
> +	imxpd->connector.funcs->destroy(&imxpd->connector);
> +
>  	kfree(imxpd->edid);
>  }
>  
> -- 
> 2.19.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch