Re: [PATCH 17/17] drm/imx: fix drm_mode_config_cleanup race condition

[Lucas Stach <l.stach@pengutronix.de>]

Hi Daniel,

On Do, 2020-02-27 at 18:29 +0100, Daniel Vetter wrote:
> On Thu, Feb 27, 2020 at 05:21:25PM +0100, Marco Felsch wrote:
> > Currently there is a race conditions if the panel can't be probed e.g.
> > it is not connected [1]. There where several attempts to fix this [2,3]
> > but non of them made it into mainline.
> > 
> > The problem is the combination of the component framework and the drm
> > framework, as Philipp already explained [1]. To fix this we need to
> > drop the devres-kmalloc and move the plain kmalloc to let the drm
> > framework free the resources upon a drm_mode_config_cleanup(). So we need
> > to implement a .destroy() callback for each component. We also need to
> > reorder the master.unbind() callback to ensure that the driver states
> > are accessible during a component.unbind() call. This reordering also
> > aligns the master.unbind() with the error-cleanup path during
> > master.bind().
> > 
> > [1] https://www.spinics.net/lists/dri-devel/msg189388.html
> > [2] https://lkml.org/lkml/2018/10/16/1148
> > [3] https://lkml.org/lkml/2019/4/2/612
> > 
> > Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
> 
> I think this collides quite badly with my managed drm device resources
> patch series I'm working on. Plus once we have that, you could use
> drmm_kzalloc and wouldn't need to sprinkle kfree() over everything.
> 
> I think at least, I haven't rolled much further than just getting the
> baseline stuff figured out. So if it's not super-pressing to get this
> patch here landed I think it'd be better to base this on top of the drmm
> series. I'm working on sending out v3, I'll cc you on the imx parts so
> you'll get pinged.

IMO this part of imx-drm has been broken for far too long already, so
we shouldn't delay this fixes series on a complete resource management
rework.

Regards,
Lucas

> Cheers, Daniel
> 
> > ---
> >  drivers/gpu/drm/imx/dw_hdmi-imx.c      | 28 ++++++++++++---------
> >  drivers/gpu/drm/imx/imx-drm-core.c     |  3 ++-
> >  drivers/gpu/drm/imx/imx-ldb.c          | 34 +++++++++++++++++---------
> >  drivers/gpu/drm/imx/imx-tve.c          | 15 +++++++++---
> >  drivers/gpu/drm/imx/ipuv3-crtc.c       | 28 ++++++++++++++++++---
> >  drivers/gpu/drm/imx/parallel-display.c | 30 ++++++++++++++++-------
> >  6 files changed, 96 insertions(+), 42 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/imx/dw_hdmi-imx.c b/drivers/gpu/drm/imx/dw_hdmi-imx.c
> > index f22cfbf9353e..86a62796c151 100644
> > --- a/drivers/gpu/drm/imx/dw_hdmi-imx.c
> > +++ b/drivers/gpu/drm/imx/dw_hdmi-imx.c
> > @@ -137,6 +137,12 @@ static int dw_hdmi_imx_atomic_check(struct drm_encoder *encoder,
> >  	return 0;
> >  }
> >  
> > +static void dw_hdmi_imx_encoder_destroy(struct drm_encoder *encoder)
> > +{
> > +	drm_encoder_cleanup(encoder);
> > +	kfree(enc_to_imx_hdmi(encoder));
> > +}
> > +
> >  static const struct drm_encoder_helper_funcs dw_hdmi_imx_encoder_helper_funcs = {
> >  	.enable     = dw_hdmi_imx_encoder_enable,
> >  	.disable    = dw_hdmi_imx_encoder_disable,
> > @@ -144,7 +150,7 @@ static const struct drm_encoder_helper_funcs dw_hdmi_imx_encoder_helper_funcs =
> >  };
> >  
> >  static const struct drm_encoder_funcs dw_hdmi_imx_encoder_funcs = {
> > -	.destroy = drm_encoder_cleanup,
> > +	.destroy = dw_hdmi_imx_encoder_destroy,
> >  };
> >  
> >  static enum drm_mode_status
> > @@ -212,7 +218,7 @@ static int dw_hdmi_imx_bind(struct device *dev, struct device *master,
> >  	if (!pdev->dev.of_node)
> >  		return -ENODEV;
> >  
> > -	hdmi = devm_kzalloc(&pdev->dev, sizeof(*hdmi), GFP_KERNEL);
> > +	hdmi = kzalloc(sizeof(*hdmi), GFP_KERNEL);
> >  	if (!hdmi)
> >  		return -ENOMEM;
> >  
> > @@ -228,12 +234,16 @@ static int dw_hdmi_imx_bind(struct device *dev, struct device *master,
> >  	 * not been registered yet.  Defer probing, and hope that
> >  	 * the required CRTC is added later.
> >  	 */
> > -	if (encoder->possible_crtcs == 0)
> > +	if (encoder->possible_crtcs == 0) {
> > +		kfree(hdmi);
> >  		return -EPROBE_DEFER;
> > +	}
> >  
> >  	ret = dw_hdmi_imx_parse_dt(hdmi);
> > -	if (ret < 0)
> > +	if (ret < 0) {
> > +		kfree(hdmi);
> >  		return ret;
> > +	}
> >  
> >  	drm_encoder_helper_add(encoder, &dw_hdmi_imx_encoder_helper_funcs);
> >  	drm_encoder_init(drm, encoder, &dw_hdmi_imx_encoder_funcs,
> > @@ -242,15 +252,9 @@ static int dw_hdmi_imx_bind(struct device *dev, struct device *master,
> >  	platform_set_drvdata(pdev, hdmi);
> >  
> >  	hdmi->hdmi = dw_hdmi_bind(pdev, encoder, plat_data);
> > -
> > -	/*
> > -	 * If dw_hdmi_bind() fails we'll never call dw_hdmi_unbind(),
> > -	 * which would have called the encoder cleanup.  Do it manually.
> > -	 */
> > -	if (IS_ERR(hdmi->hdmi)) {
> > +	/* Don't call kfree() here, this is done by the .destroy() handler. */
> > +	if (IS_ERR(hdmi->hdmi))
> >  		ret = PTR_ERR(hdmi->hdmi);
> > -		drm_encoder_cleanup(encoder);
> > -	}
> >  
> >  	return ret;
> >  }
> > diff --git a/drivers/gpu/drm/imx/imx-drm-core.c b/drivers/gpu/drm/imx/imx-drm-core.c
> > index 9979547ca883..feab6eb9e7e5 100644
> > --- a/drivers/gpu/drm/imx/imx-drm-core.c
> > +++ b/drivers/gpu/drm/imx/imx-drm-core.c
> > @@ -275,9 +275,10 @@ static void imx_drm_unbind(struct device *dev)
> >  
> >  	drm_kms_helper_poll_fini(drm);
> >  
> > +	component_unbind_all(drm->dev, drm);
> > +
> >  	drm_mode_config_cleanup(drm);
> >  
> > -	component_unbind_all(drm->dev, drm);
> >  	dev_set_drvdata(dev, NULL);
> >  
> >  	drm_dev_put(drm);
> > diff --git a/drivers/gpu/drm/imx/imx-ldb.c b/drivers/gpu/drm/imx/imx-ldb.c
> > index 5e6c1b09dbfa..4a5d31da592a 100644
> > --- a/drivers/gpu/drm/imx/imx-ldb.c
> > +++ b/drivers/gpu/drm/imx/imx-ldb.c
> > @@ -140,6 +140,8 @@ static void imx_ldb_connector_destroy(struct drm_connector *connector)
> >  	i2c_put_adapter(imx_ldb_con->ddc);
> >  	/* avoid dangling pointers */
> >  	imx_ldb_con->ldb_channel = NULL;
> > +	kfree(imx_ldb_con->edid);
> > +	kfree(imx_ldb_con);
> >  }
> >  
> >  static int imx_ldb_connector_get_modes(struct drm_connector *connector)
> > @@ -184,6 +186,7 @@ static void imx_ldb_encoder_destroy(struct drm_encoder *encoder)
> >  	drm_encoder_cleanup(encoder);
> >  	/* avoid dangling pointers */
> >  	channel->ldb = NULL;
> > +	kfree(channel);
> >  }
> >  
> >  static void imx_ldb_set_clock(struct imx_ldb *ldb, int mux, int chno,
> > @@ -502,9 +505,8 @@ static int imx_ldb_panel_ddc(struct device *dev,
> >  		edidp = of_get_property(child, "edid",
> >  					&connector->edid_len);
> >  		if (edidp) {
> > -			connector->edid = devm_kmemdup(dev, edidp,
> > -						       connector->edid_len,
> > -						       GFP_KERNEL);
> > +			connector->edid = kmemdup(edidp, connector->edid_len,
> > +						  GFP_KERNEL);
> >  		} else if (!channel->panel) {
> >  			/* fallback to display-timings node */
> >  			ret = of_get_drm_display_mode(child,
> > @@ -525,7 +527,7 @@ static int imx_ldb_setup_channel(struct device *dev,
> >  				 int channel_number)
> >  {
> >  	struct imx_ldb_channel *channel;
> > -	struct imx_ldb_connector *imx_ldb_con;
> > +	struct imx_ldb_connector *imx_ldb_con = NULL;
> >  	struct drm_encoder *encoder;
> >  	struct drm_connector *connector = NULL;
> >  	int bus_format;
> > @@ -537,7 +539,7 @@ static int imx_ldb_setup_channel(struct device *dev,
> >  	 * 3) Register it with the DRM framework
> >  	 * 4) Attach bridge or connector to encoder
> >  	 */
> > -	channel = devm_kzalloc(dev, sizeof(*channel), GFP_KERNEL);
> > +	channel = kzalloc(sizeof(*channel), GFP_KERNEL);
> >  	if (!channel)
> >  		return -ENOMEM;
> >  
> > @@ -554,17 +556,19 @@ static int imx_ldb_setup_channel(struct device *dev,
> >  					  ldb->lvds_mux ? 4 : 2, 0,
> >  					  &channel->panel, &channel->bridge);
> >  	if (ret && ret != -ENODEV)
> > -		return ret;
> > +		goto err_free;
> >  
> >  	/* panel ddc only if there is no bridge */
> >  	if (!channel->bridge) {
> > -		imx_ldb_con = devm_kzalloc(dev, sizeof(*connector), GFP_KERNEL);
> > -		if (!imx_ldb_con)
> > -			return -ENOMEM;
> > +		imx_ldb_con = kzalloc(sizeof(*connector), GFP_KERNEL);
> > +		if (!imx_ldb_con) {
> > +			ret = -ENOMEM;
> > +			goto err_free;
> > +		}
> >  
> >  		ret = imx_ldb_panel_ddc(dev, channel, imx_ldb_con, child);
> >  		if (ret)
> > -			return ret;
> > +			goto err_free;
> >  
> >  		imx_ldb_con->ldb_channel = channel;
> >  		connector = &imx_ldb_con->connector;
> > @@ -628,7 +632,7 @@ static int imx_ldb_setup_channel(struct device *dev,
> >  		ret = drm_bridge_attach(encoder, channel->bridge, NULL);
> >  		if (ret) {
> >  			DRM_ERROR("Failed to initialize bridge with drm\n");
> > -			goto err_put_ddc;
> > +			goto err_out;
> >  		}
> >  	} else {
> >  		drm_connector_attach_encoder(connector, encoder);
> > @@ -637,7 +641,7 @@ static int imx_ldb_setup_channel(struct device *dev,
> >  	if (channel->panel) {
> >  		ret = drm_panel_attach(channel->panel, connector);
> >  		if (ret)
> > -			goto err_put_ddc;
> > +			goto err_out;
> >  	}
> >  
> >  	return 0;
> > @@ -645,6 +649,12 @@ static int imx_ldb_setup_channel(struct device *dev,
> >  err_put_ddc:
> >  	if (imx_ldb_con)
> >  		i2c_put_adapter(imx_ldb_con->ddc);
> > +err_free:
> > +	if (imx_ldb_con)
> > +		kfree(imx_ldb_con->edid);
> > +	kfree(imx_ldb_con);
> > +	kfree(channel);
> > +err_out:
> >  	return ret;
> >  }
> >  
> > diff --git a/drivers/gpu/drm/imx/imx-tve.c b/drivers/gpu/drm/imx/imx-tve.c
> > index a7a05c47f68b..15ff5f35ff0e 100644
> > --- a/drivers/gpu/drm/imx/imx-tve.c
> > +++ b/drivers/gpu/drm/imx/imx-tve.c
> > @@ -241,6 +241,7 @@ static void imx_tve_connector_destroy(struct drm_connector *connector)
> >  	i2c_put_adapter(tvec->ddc);
> >  	/* avoid dangling pointers */
> >  	tvec->tve = NULL;
> > +	kfree(tvec);
> >  }
> >  
> >  static int imx_tve_connector_get_modes(struct drm_connector *connector)
> > @@ -292,6 +293,7 @@ static void imx_tve_encoder_destroy(struct drm_encoder *encoder)
> >  	drm_encoder_cleanup(encoder);
> >  	/* avoid dangling pointers */
> >  	tvee->tve = NULL;
> > +	kfree(tvee);
> >  }
> >  
> >  static void imx_tve_encoder_mode_set(struct drm_encoder *encoder,
> > @@ -577,13 +579,15 @@ static int imx_tve_bind(struct device *dev, struct device *master, void *data)
> >  	struct imx_tve_connector *tvec;
> >  	int ret;
> >  
> > -	tvee = devm_kzalloc(dev, sizeof(*tvee), GFP_KERNEL);
> > +	tvee = kzalloc(sizeof(*tvee), GFP_KERNEL);
> >  	if (!tvee)
> >  		return -ENOMEM;
> >  
> > -	tvec = devm_kzalloc(dev, sizeof(*tvec), GFP_KERNEL);
> > -	if (!tvec)
> > -		return -ENOMEM;
> > +	tvec = kzalloc(sizeof(*tvec), GFP_KERNEL);
> > +	if (!tvec) {
> > +		ret = -ENOMEM;
> > +		goto err_free;
> > +	}
> >  
> >  	tvee->tve = imx_tve;
> >  	tvec->tve = imx_tve;
> > @@ -602,6 +606,9 @@ static int imx_tve_bind(struct device *dev, struct device *master, void *data)
> >  
> >  err_put_ddc:
> >  	i2c_put_adapter(tvec->ddc);
> > +err_free:
> > +	kfree(tvec);
> > +	kfree(tvee);
> >  	return ret;
> >  }
> >  
> > diff --git a/drivers/gpu/drm/imx/ipuv3-crtc.c b/drivers/gpu/drm/imx/ipuv3-crtc.c
> > index 63c0284f8b3c..2d24677f7fef 100644
> > --- a/drivers/gpu/drm/imx/ipuv3-crtc.c
> > +++ b/drivers/gpu/drm/imx/ipuv3-crtc.c
> > @@ -105,6 +105,12 @@ static void ipu_crtc_atomic_disable(struct drm_crtc *crtc,
> >  	spin_unlock_irq(&crtc->dev->event_lock);
> >  }
> >  
> > +static void imx_drm_crtc_destroy(struct drm_crtc *crtc)
> > +{
> > +	drm_crtc_cleanup(crtc);
> > +	kfree(to_ipu_crtc(crtc));
> > +}
> > +
> >  static void imx_drm_crtc_reset(struct drm_crtc *crtc)
> >  {
> >  	struct imx_crtc_state *state;
> > @@ -166,7 +172,7 @@ static void ipu_disable_vblank(struct drm_crtc *crtc)
> >  
> >  static const struct drm_crtc_funcs ipu_crtc_funcs = {
> >  	.set_config = drm_atomic_helper_set_config,
> > -	.destroy = drm_crtc_cleanup,
> > +	.destroy = imx_drm_crtc_destroy,
> >  	.page_flip = drm_atomic_helper_page_flip,
> >  	.reset = imx_drm_crtc_reset,
> >  	.atomic_duplicate_state = imx_drm_crtc_duplicate_state,
> > @@ -357,7 +363,8 @@ static int ipu_get_resources(struct ipu_crtc *ipu_crtc,
> >  }
> >  
> >  static int ipu_crtc_init(struct ipu_crtc *ipu_crtc,
> > -	struct ipu_client_platformdata *pdata, struct drm_device *drm)
> > +			 struct ipu_client_platformdata *pdata,
> > +			 struct drm_device *drm)
> >  {
> >  	struct ipu_soc *ipu = dev_get_drvdata(ipu_crtc->dev->parent);
> >  	struct drm_crtc *crtc = &ipu_crtc->base;
> > @@ -437,10 +444,11 @@ static int ipu_drm_bind(struct device *dev, struct device *master, void *data)
> >  {
> >  	struct ipu_client_platformdata *pdata = dev->platform_data;
> >  	struct drm_device *drm = data;
> > +	struct drm_crtc *registered_crtc = NULL;
> >  	struct ipu_crtc *ipu_crtc;
> >  	int ret;
> >  
> > -	ipu_crtc = devm_kzalloc(dev, sizeof(*ipu_crtc), GFP_KERNEL);
> > +	ipu_crtc = kzalloc(sizeof(*ipu_crtc), GFP_KERNEL);
> >  	if (!ipu_crtc)
> >  		return -ENOMEM;
> >  
> > @@ -448,11 +456,23 @@ static int ipu_drm_bind(struct device *dev, struct device *master, void *data)
> >  
> >  	ret = ipu_crtc_init(ipu_crtc, pdata, drm);
> >  	if (ret)
> > -		return ret;
> > +		goto err;
> >  
> >  	dev_set_drvdata(dev, ipu_crtc);
> >  
> >  	return 0;
> > +
> > +err:
> > +	drm_for_each_crtc(registered_crtc, drm) {
> > +		/*
> > +		 * The crtc was registered with the drm core framework if we
> > +		 * enter here. So let the core .destroy() helper cleanup the
> > +		 * code.
> > +		 */
> > +		return ret;
> > +	}
> > +	kfree(ipu_crtc);
> > +	return ret;
> >  }
> >  
> >  static void ipu_drm_unbind(struct device *dev, struct device *master,
> > diff --git a/drivers/gpu/drm/imx/parallel-display.c b/drivers/gpu/drm/imx/parallel-display.c
> > index 78703b15c7cf..3e247383a498 100644
> > --- a/drivers/gpu/drm/imx/parallel-display.c
> > +++ b/drivers/gpu/drm/imx/parallel-display.c
> > @@ -55,6 +55,8 @@ static void imx_pd_connector_destroy(struct drm_connector *connector)
> >  	imx_drm_connector_destroy(connector);
> >  	/* avoid dangling pointer */
> >  	imxpc->imxpd = NULL;
> > +	kfree(imxpc->edid);
> > +	kfree(imxpc);
> >  }
> >  
> >  static int imx_pd_connector_get_modes(struct drm_connector *connector)
> > @@ -102,6 +104,7 @@ static void imx_pd_encoder_destroy(struct drm_encoder *encoder)
> >  	if (imxpd->panel)
> >  		drm_panel_detach(imxpd->panel);
> >  	drm_encoder_cleanup(encoder);
> > +	kfree(imxpd);
> >  }
> >  
> >  static void imx_pd_encoder_enable(struct drm_encoder *encoder)
> > @@ -225,31 +228,32 @@ static int imx_pd_bind(struct device *dev, struct device *master, void *data)
> >  	struct device_node *np = dev->of_node;
> >  	const u8 *edidp;
> >  	struct imx_parallel_display *imxpd;
> > -	struct imx_parallel_connector *imxpc;
> > +	struct imx_parallel_connector *imxpc = NULL;
> >  	int ret;
> >  	u32 bus_format = 0;
> >  	const char *fmt;
> >  
> > -	imxpd = devm_kzalloc(dev, sizeof(*imxpd), GFP_KERNEL);
> > +	imxpd = kzalloc(sizeof(*imxpd), GFP_KERNEL);
> >  	if (!imxpd)
> >  		return -ENOMEM;
> >  
> >  	/* port@1 is the output port */
> >  	ret = drm_of_find_panel_or_bridge(np, 1, 0, &imxpd->panel, &imxpd->bridge);
> >  	if (ret && ret != -ENODEV)
> > -		return ret;
> > +		goto err_free;
> >  
> >  	if (!imxpd->bridge) {
> > -		imxpc = devm_kzalloc(dev, sizeof(*imxpc), GFP_KERNEL);
> > -		if (!imxpc)
> > -			return -ENOMEM;
> > +		imxpc = kzalloc(sizeof(*imxpc), GFP_KERNEL);
> > +		if (!imxpc) {
> > +			ret = -ENOMEM;
> > +			goto err_free;
> > +		}
> >  
> >  		imxpc->imxpd = imxpd;
> >  
> >  		edidp = of_get_property(np, "edid", &imxpc->edid_len);
> >  		if (edidp)
> > -			imxpc->edid = devm_kmemdup(dev, edidp, imxpc->edid_len,
> > -						   GFP_KERNEL);
> > +			imxpc->edid = kmemdup(edidp, imxpc->edid_len, GFP_KERNEL);
> >  	}
> >  
> >  	ret = of_property_read_string(np, "interface-pix-fmt", &fmt);
> > @@ -269,9 +273,17 @@ static int imx_pd_bind(struct device *dev, struct device *master, void *data)
> >  
> >  	ret = imx_pd_register(drm, imxpd, imxpc);
> >  	if (ret)
> > -		return ret;
> > +		goto err_free;
> >  
> >  	return imx_pd_attach(drm, imxpd, imxpc);
> > +
> > +err_free:
> > +	if (imxpc)
> > +		kfree(imxpc->edid);
> > +	kfree(imxpc);
> > +	kfree(imxpd);
> > +
> > +	return ret;
> >  }
> >  
> >  static const struct component_ops imx_pd_ops = {
> > -- 
> > 2.20.1
> > 

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