[PATCH v3] drm/cma-helper: Fix crash in fbdev error path

[PATCH v3] drm/cma-helper: Fix crash in fbdev error path

[Noralf Trønnes]

Sergey Suloev reported a crash happening in drm_client_dev_hotplug()
when fbdev had failed to register.

[    9.124598] vc4_hdmi 3f902000.hdmi: ASoC: Failed to create component debugfs directory
[    9.147667] vc4_hdmi 3f902000.hdmi: vc4-hdmi-hifi <-> 3f902000.hdmi mapping ok
[    9.155184] vc4_hdmi 3f902000.hdmi: ASoC: no DMI vendor name!
[    9.166544] vc4-drm soc:gpu: bound 3f902000.hdmi (ops vc4_hdmi_ops [vc4])
[    9.173840] vc4-drm soc:gpu: bound 3f806000.vec (ops vc4_vec_ops [vc4])
[    9.181029] vc4-drm soc:gpu: bound 3f004000.txp (ops vc4_txp_ops [vc4])
[    9.188519] vc4-drm soc:gpu: bound 3f400000.hvs (ops vc4_hvs_ops [vc4])
[    9.195690] vc4-drm soc:gpu: bound 3f206000.pixelvalve (ops vc4_crtc_ops [vc4])
[    9.203523] vc4-drm soc:gpu: bound 3f207000.pixelvalve (ops vc4_crtc_ops [vc4])
[    9.215032] vc4-drm soc:gpu: bound 3f807000.pixelvalve (ops vc4_crtc_ops [vc4])
[    9.274785] vc4-drm soc:gpu: bound 3fc00000.v3d (ops vc4_v3d_ops [vc4])
[    9.290246] [drm] Initialized vc4 0.0.0 20140616 for soc:gpu on minor 0
[    9.297464] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[    9.304600] [drm] Driver supports precise vblank timestamp query.
[    9.382856] vc4-drm soc:gpu: [drm:drm_fb_helper_fbdev_setup [drm_kms_helper]] *ERROR* Failed to set fbdev configuration
[   10.404937] Unable to handle kernel paging request at virtual address 00330a656369768a
[   10.441620] [00330a656369768a] address between user and kernel address ranges
[   10.449087] Internal error: Oops: 96000004 [#1] PREEMPT SMP
[   10.454762] Modules linked in: brcmfmac vc4 drm_kms_helper cfg80211 drm rfkill smsc95xx brcmutil usbnet drm_panel_orientation_quirks raspberrypi_hwmon bcm2835_dma crc32_ce pwm_bcm2835 bcm2835_rng virt_dma rng_core i2c_bcm2835 ip_tables x_tables ipv6
[   10.477296] CPU: 2 PID: 45 Comm: kworker/2:1 Not tainted 4.19.0-rc5 #3
[   10.483934] Hardware name: Raspberry Pi 3 Model B Rev 1.2 (DT)
[   10.489966] Workqueue: events output_poll_execute [drm_kms_helper]
[   10.596515] Process kworker/2:1 (pid: 45, stack limit = 0x000000007e8924dc)
[   10.603590] Call trace:
[   10.606259]  drm_client_dev_hotplug+0x5c/0xb0 [drm]
[   10.611303]  drm_kms_helper_hotplug_event+0x30/0x40 [drm_kms_helper]
[   10.617849]  output_poll_execute+0xc4/0x1e0 [drm_kms_helper]
[   10.623616]  process_one_work+0x1c8/0x318
[   10.627695]  worker_thread+0x48/0x428
[   10.631420]  kthread+0xf8/0x128
[   10.634615]  ret_from_fork+0x10/0x18
[   10.638255] Code: 54000220 f9401261 aa1303e0 b4000141 (f9400c21)
[   10.644456] ---[ end trace c75b4a4b0e141908 ]---

The reason for this is that drm_fbdev_cma_init() removes the drm_client
when fbdev registration fails, but it doesn't remove the client from the
drm_device client list. So the client list now has a pointer that points
into the unknown and we have a 'use after free' situation.

Split drm_client_new() into drm_client_init() and drm_client_add() to fix
removal in the error path.

Fixes: 894a677f4b3e ("drm/cma-helper: Use the generic fbdev emulation")
Reported-by: Sergey Suloev <ssuloev@orpaltech.com>
Cc: Stefan Wahren <stefan.wahren@i2se.com>
Cc: Eric Anholt <eric@anholt.net>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---

Changes since version 2:
- Fix drm_client_new() ref in docs (Daniel)
- Expand drm_client_add() docs (Daniel)

Changes since version 1:
- Split drm_client_new() instead of letting drm_client hang around (Daniel)

 drivers/gpu/drm/drm_client.c        | 35 ++++++++++++++++++++++++++---------
 drivers/gpu/drm/drm_fb_cma_helper.c |  4 +++-
 drivers/gpu/drm/drm_fb_helper.c     |  4 +++-
 include/drm/drm_client.h            |  5 +++--
 4 files changed, 35 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
index 17d9a64e885e..fc03d26fcacc 100644
--- a/drivers/gpu/drm/drm_client.c
+++ b/drivers/gpu/drm/drm_client.c
@@ -63,20 +63,21 @@ static void drm_client_close(struct drm_client_dev *client)
 EXPORT_SYMBOL(drm_client_close);
 
 /**
- * drm_client_new - Create a DRM client
+ * drm_client_init - Initialise a DRM client
  * @dev: DRM device
  * @client: DRM client
  * @name: Client name
  * @funcs: DRM client functions (optional)
  *
+ * This initialises the client and opens a &drm_file. Use drm_client_add() to complete the process.
  * The caller needs to hold a reference on @dev before calling this function.
  * The client is freed when the &drm_device is unregistered. See drm_client_release().
  *
  * Returns:
  * Zero on success or negative error code on failure.
  */
-int drm_client_new(struct drm_device *dev, struct drm_client_dev *client,
-		   const char *name, const struct drm_client_funcs *funcs)
+int drm_client_init(struct drm_device *dev, struct drm_client_dev *client,
+		    const char *name, const struct drm_client_funcs *funcs)
 {
 	int ret;
 
@@ -95,10 +96,6 @@ int drm_client_new(struct drm_device *dev, struct drm_client_dev *client,
 	if (ret)
 		goto err_put_module;
 
-	mutex_lock(&dev->clientlist_mutex);
-	list_add(&client->list, &dev->clientlist);
-	mutex_unlock(&dev->clientlist_mutex);
-
 	drm_dev_get(dev);
 
 	return 0;
@@ -109,13 +106,33 @@ int drm_client_new(struct drm_device *dev, struct drm_client_dev *client,
 
 	return ret;
 }
-EXPORT_SYMBOL(drm_client_new);
+EXPORT_SYMBOL(drm_client_init);
+
+/**
+ * drm_client_add - Add client to the device list
+ * @client: DRM client
+ *
+ * Add the client to the &drm_device client list to activate its callbacks.
+ * @client must be initialized by a call to drm_client_init(). After
+ * drm_client_add() it is no longer permissible to call drm_client_release()
+ * directly (outside the unregister callback), instead cleanup will happen
+ * automatically on driver unload.
+ */
+void drm_client_add(struct drm_client_dev *client)
+{
+	struct drm_device *dev = client->dev;
+
+	mutex_lock(&dev->clientlist_mutex);
+	list_add(&client->list, &dev->clientlist);
+	mutex_unlock(&dev->clientlist_mutex);
+}
+EXPORT_SYMBOL(drm_client_add);
 
 /**
  * drm_client_release - Release DRM client resources
  * @client: DRM client
  *
- * Releases resources by closing the &drm_file that was opened by drm_client_new().
+ * Releases resources by closing the &drm_file that was opened by drm_client_init().
  * It is called automatically if the &drm_client_funcs.unregister callback is _not_ set.
  *
  * This function should only be called from the unregister callback. An exception
diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
index 47e0e2f6642d..fb0dfc62b1b6 100644
--- a/drivers/gpu/drm/drm_fb_cma_helper.c
+++ b/drivers/gpu/drm/drm_fb_cma_helper.c
@@ -167,7 +167,7 @@ struct drm_fbdev_cma *drm_fbdev_cma_init(struct drm_device *dev,
 
 	fb_helper = &fbdev_cma->fb_helper;
 
-	ret = drm_client_new(dev, &fb_helper->client, "fbdev", NULL);
+	ret = drm_client_init(dev, &fb_helper->client, "fbdev", NULL);
 	if (ret)
 		goto err_free;
 
@@ -176,6 +176,8 @@ struct drm_fbdev_cma *drm_fbdev_cma_init(struct drm_device *dev,
 	if (ret)
 		goto err_client_put;
 
+	drm_client_add(&fb_helper->client);
+
 	return fbdev_cma;
 
 err_client_put:
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index a504a5e05676..e9095537e0c0 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -3229,13 +3229,15 @@ int drm_fbdev_generic_setup(struct drm_device *dev, unsigned int preferred_bpp)
 	if (!fb_helper)
 		return -ENOMEM;
 
-	ret = drm_client_new(dev, &fb_helper->client, "fbdev", &drm_fbdev_client_funcs);
+	ret = drm_client_init(dev, &fb_helper->client, "fbdev", &drm_fbdev_client_funcs);
 	if (ret) {
 		kfree(fb_helper);
 		DRM_DEV_ERROR(dev->dev, "Failed to register client: %d\n", ret);
 		return ret;
 	}
 
+	drm_client_add(&fb_helper->client);
+
 	fb_helper->preferred_bpp = preferred_bpp;
 
 	ret = drm_fbdev_client_hotplug(&fb_helper->client);
diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
index 989f8e52864d..971bb7853776 100644
--- a/include/drm/drm_client.h
+++ b/include/drm/drm_client.h
@@ -87,9 +87,10 @@ struct drm_client_dev {
 	struct drm_file *file;
 };
 
-int drm_client_new(struct drm_device *dev, struct drm_client_dev *client,
-		   const char *name, const struct drm_client_funcs *funcs);
+int drm_client_init(struct drm_device *dev, struct drm_client_dev *client,
+		    const char *name, const struct drm_client_funcs *funcs);
 void drm_client_release(struct drm_client_dev *client);
+void drm_client_add(struct drm_client_dev *client);
 
 void drm_client_dev_unregister(struct drm_device *dev);
 void drm_client_dev_hotplug(struct drm_device *dev);
-- 
2.15.1

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Re: [PATCH v3] drm/cma-helper: Fix crash in fbdev error path

[Noralf Trønnes]

Den 01.10.2018 21.45, skrev Noralf Trønnes:
> Sergey Suloev reported a crash happening in drm_client_dev_hotplug()
> when fbdev had failed to register.
>
> [    9.124598] vc4_hdmi 3f902000.hdmi: ASoC: Failed to create component debugfs directory
> [    9.147667] vc4_hdmi 3f902000.hdmi: vc4-hdmi-hifi <-> 3f902000.hdmi mapping ok
> [    9.155184] vc4_hdmi 3f902000.hdmi: ASoC: no DMI vendor name!
> [    9.166544] vc4-drm soc:gpu: bound 3f902000.hdmi (ops vc4_hdmi_ops [vc4])
> [    9.173840] vc4-drm soc:gpu: bound 3f806000.vec (ops vc4_vec_ops [vc4])
> [    9.181029] vc4-drm soc:gpu: bound 3f004000.txp (ops vc4_txp_ops [vc4])
> [    9.188519] vc4-drm soc:gpu: bound 3f400000.hvs (ops vc4_hvs_ops [vc4])
> [    9.195690] vc4-drm soc:gpu: bound 3f206000.pixelvalve (ops vc4_crtc_ops [vc4])
> [    9.203523] vc4-drm soc:gpu: bound 3f207000.pixelvalve (ops vc4_crtc_ops [vc4])
> [    9.215032] vc4-drm soc:gpu: bound 3f807000.pixelvalve (ops vc4_crtc_ops [vc4])
> [    9.274785] vc4-drm soc:gpu: bound 3fc00000.v3d (ops vc4_v3d_ops [vc4])
> [    9.290246] [drm] Initialized vc4 0.0.0 20140616 for soc:gpu on minor 0
> [    9.297464] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
> [    9.304600] [drm] Driver supports precise vblank timestamp query.
> [    9.382856] vc4-drm soc:gpu: [drm:drm_fb_helper_fbdev_setup [drm_kms_helper]] *ERROR* Failed to set fbdev configuration
> [   10.404937] Unable to handle kernel paging request at virtual address 00330a656369768a
> [   10.441620] [00330a656369768a] address between user and kernel address ranges
> [   10.449087] Internal error: Oops: 96000004 [#1] PREEMPT SMP
> [   10.454762] Modules linked in: brcmfmac vc4 drm_kms_helper cfg80211 drm rfkill smsc95xx brcmutil usbnet drm_panel_orientation_quirks raspberrypi_hwmon bcm2835_dma crc32_ce pwm_bcm2835 bcm2835_rng virt_dma rng_core i2c_bcm2835 ip_tables x_tables ipv6
> [   10.477296] CPU: 2 PID: 45 Comm: kworker/2:1 Not tainted 4.19.0-rc5 #3
> [   10.483934] Hardware name: Raspberry Pi 3 Model B Rev 1.2 (DT)
> [   10.489966] Workqueue: events output_poll_execute [drm_kms_helper]
> [   10.596515] Process kworker/2:1 (pid: 45, stack limit = 0x000000007e8924dc)
> [   10.603590] Call trace:
> [   10.606259]  drm_client_dev_hotplug+0x5c/0xb0 [drm]
> [   10.611303]  drm_kms_helper_hotplug_event+0x30/0x40 [drm_kms_helper]
> [   10.617849]  output_poll_execute+0xc4/0x1e0 [drm_kms_helper]
> [   10.623616]  process_one_work+0x1c8/0x318
> [   10.627695]  worker_thread+0x48/0x428
> [   10.631420]  kthread+0xf8/0x128
> [   10.634615]  ret_from_fork+0x10/0x18
> [   10.638255] Code: 54000220 f9401261 aa1303e0 b4000141 (f9400c21)
> [   10.644456] ---[ end trace c75b4a4b0e141908 ]---
>
> The reason for this is that drm_fbdev_cma_init() removes the drm_client
> when fbdev registration fails, but it doesn't remove the client from the
> drm_device client list. So the client list now has a pointer that points
> into the unknown and we have a 'use after free' situation.
>
> Split drm_client_new() into drm_client_init() and drm_client_add() to fix
> removal in the error path.
>
> Fixes: 894a677f4b3e ("drm/cma-helper: Use the generic fbdev emulation")
> Reported-by: Sergey Suloev <ssuloev@orpaltech.com>
> Cc: Stefan Wahren <stefan.wahren@i2se.com>
> Cc: Eric Anholt <eric@anholt.net>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---

Applied to drm-misc-fixes, thanks for the review.

Noralf.

> Changes since version 2:
> - Fix drm_client_new() ref in docs (Daniel)
> - Expand drm_client_add() docs (Daniel)
>
> Changes since version 1:
> - Split drm_client_new() instead of letting drm_client hang around (Daniel)
>
>   drivers/gpu/drm/drm_client.c        | 35 ++++++++++++++++++++++++++---------
>   drivers/gpu/drm/drm_fb_cma_helper.c |  4 +++-
>   drivers/gpu/drm/drm_fb_helper.c     |  4 +++-
>   include/drm/drm_client.h            |  5 +++--
>   4 files changed, 35 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
> index 17d9a64e885e..fc03d26fcacc 100644
> --- a/drivers/gpu/drm/drm_client.c
> +++ b/drivers/gpu/drm/drm_client.c
> @@ -63,20 +63,21 @@ static void drm_client_close(struct drm_client_dev *client)
>   EXPORT_SYMBOL(drm_client_close);
>   
>   /**
> - * drm_client_new - Create a DRM client
> + * drm_client_init - Initialise a DRM client
>    * @dev: DRM device
>    * @client: DRM client
>    * @name: Client name
>    * @funcs: DRM client functions (optional)
>    *
> + * This initialises the client and opens a &drm_file. Use drm_client_add() to complete the process.
>    * The caller needs to hold a reference on @dev before calling this function.
>    * The client is freed when the &drm_device is unregistered. See drm_client_release().
>    *
>    * Returns:
>    * Zero on success or negative error code on failure.
>    */
> -int drm_client_new(struct drm_device *dev, struct drm_client_dev *client,
> -		   const char *name, const struct drm_client_funcs *funcs)
> +int drm_client_init(struct drm_device *dev, struct drm_client_dev *client,
> +		    const char *name, const struct drm_client_funcs *funcs)
>   {
>   	int ret;
>   
> @@ -95,10 +96,6 @@ int drm_client_new(struct drm_device *dev, struct drm_client_dev *client,
>   	if (ret)
>   		goto err_put_module;
>   
> -	mutex_lock(&dev->clientlist_mutex);
> -	list_add(&client->list, &dev->clientlist);
> -	mutex_unlock(&dev->clientlist_mutex);
> -
>   	drm_dev_get(dev);
>   
>   	return 0;
> @@ -109,13 +106,33 @@ int drm_client_new(struct drm_device *dev, struct drm_client_dev *client,
>   
>   	return ret;
>   }
> -EXPORT_SYMBOL(drm_client_new);
> +EXPORT_SYMBOL(drm_client_init);
> +
> +/**
> + * drm_client_add - Add client to the device list
> + * @client: DRM client
> + *
> + * Add the client to the &drm_device client list to activate its callbacks.
> + * @client must be initialized by a call to drm_client_init(). After
> + * drm_client_add() it is no longer permissible to call drm_client_release()
> + * directly (outside the unregister callback), instead cleanup will happen
> + * automatically on driver unload.
> + */
> +void drm_client_add(struct drm_client_dev *client)
> +{
> +	struct drm_device *dev = client->dev;
> +
> +	mutex_lock(&dev->clientlist_mutex);
> +	list_add(&client->list, &dev->clientlist);
> +	mutex_unlock(&dev->clientlist_mutex);
> +}
> +EXPORT_SYMBOL(drm_client_add);
>   
>   /**
>    * drm_client_release - Release DRM client resources
>    * @client: DRM client
>    *
> - * Releases resources by closing the &drm_file that was opened by drm_client_new().
> + * Releases resources by closing the &drm_file that was opened by drm_client_init().
>    * It is called automatically if the &drm_client_funcs.unregister callback is _not_ set.
>    *
>    * This function should only be called from the unregister callback. An exception
> diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
> index 47e0e2f6642d..fb0dfc62b1b6 100644
> --- a/drivers/gpu/drm/drm_fb_cma_helper.c
> +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
> @@ -167,7 +167,7 @@ struct drm_fbdev_cma *drm_fbdev_cma_init(struct drm_device *dev,
>   
>   	fb_helper = &fbdev_cma->fb_helper;
>   
> -	ret = drm_client_new(dev, &fb_helper->client, "fbdev", NULL);
> +	ret = drm_client_init(dev, &fb_helper->client, "fbdev", NULL);
>   	if (ret)
>   		goto err_free;
>   
> @@ -176,6 +176,8 @@ struct drm_fbdev_cma *drm_fbdev_cma_init(struct drm_device *dev,
>   	if (ret)
>   		goto err_client_put;
>   
> +	drm_client_add(&fb_helper->client);
> +
>   	return fbdev_cma;
>   
>   err_client_put:
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index a504a5e05676..e9095537e0c0 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -3229,13 +3229,15 @@ int drm_fbdev_generic_setup(struct drm_device *dev, unsigned int preferred_bpp)
>   	if (!fb_helper)
>   		return -ENOMEM;
>   
> -	ret = drm_client_new(dev, &fb_helper->client, "fbdev", &drm_fbdev_client_funcs);
> +	ret = drm_client_init(dev, &fb_helper->client, "fbdev", &drm_fbdev_client_funcs);
>   	if (ret) {
>   		kfree(fb_helper);
>   		DRM_DEV_ERROR(dev->dev, "Failed to register client: %d\n", ret);
>   		return ret;
>   	}
>   
> +	drm_client_add(&fb_helper->client);
> +
>   	fb_helper->preferred_bpp = preferred_bpp;
>   
>   	ret = drm_fbdev_client_hotplug(&fb_helper->client);
> diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
> index 989f8e52864d..971bb7853776 100644
> --- a/include/drm/drm_client.h
> +++ b/include/drm/drm_client.h
> @@ -87,9 +87,10 @@ struct drm_client_dev {
>   	struct drm_file *file;
>   };
>   
> -int drm_client_new(struct drm_device *dev, struct drm_client_dev *client,
> -		   const char *name, const struct drm_client_funcs *funcs);
> +int drm_client_init(struct drm_device *dev, struct drm_client_dev *client,
> +		    const char *name, const struct drm_client_funcs *funcs);
>   void drm_client_release(struct drm_client_dev *client);
> +void drm_client_add(struct drm_client_dev *client);
>   
>   void drm_client_dev_unregister(struct drm_device *dev);
>   void drm_client_dev_hotplug(struct drm_device *dev);

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Re: [PATCH v3] drm/cma-helper: Fix crash in fbdev error path

[Sergey Suloev]

This doesn't seem to fix the initially reported issue. The problem still 
exists with 4.19.

On 10/2/18 2:14 PM, Noralf Trønnes wrote:
>
> Den 01.10.2018 21.45, skrev Noralf Trønnes:
>> Sergey Suloev reported a crash happening in drm_client_dev_hotplug()
>> when fbdev had failed to register.
>>
>> [    9.124598] vc4_hdmi 3f902000.hdmi: ASoC: Failed to create 
>> component debugfs directory
>> [    9.147667] vc4_hdmi 3f902000.hdmi: vc4-hdmi-hifi <-> 
>> 3f902000.hdmi mapping ok
>> [    9.155184] vc4_hdmi 3f902000.hdmi: ASoC: no DMI vendor name!
>> [    9.166544] vc4-drm soc:gpu: bound 3f902000.hdmi (ops vc4_hdmi_ops 
>> [vc4])
>> [    9.173840] vc4-drm soc:gpu: bound 3f806000.vec (ops vc4_vec_ops 
>> [vc4])
>> [    9.181029] vc4-drm soc:gpu: bound 3f004000.txp (ops vc4_txp_ops 
>> [vc4])
>> [    9.188519] vc4-drm soc:gpu: bound 3f400000.hvs (ops vc4_hvs_ops 
>> [vc4])
>> [    9.195690] vc4-drm soc:gpu: bound 3f206000.pixelvalve (ops 
>> vc4_crtc_ops [vc4])
>> [    9.203523] vc4-drm soc:gpu: bound 3f207000.pixelvalve (ops 
>> vc4_crtc_ops [vc4])
>> [    9.215032] vc4-drm soc:gpu: bound 3f807000.pixelvalve (ops 
>> vc4_crtc_ops [vc4])
>> [    9.274785] vc4-drm soc:gpu: bound 3fc00000.v3d (ops vc4_v3d_ops 
>> [vc4])
>> [    9.290246] [drm] Initialized vc4 0.0.0 20140616 for soc:gpu on 
>> minor 0
>> [    9.297464] [drm] Supports vblank timestamp caching Rev 2 
>> (21.10.2013).
>> [    9.304600] [drm] Driver supports precise vblank timestamp query.
>> [    9.382856] vc4-drm soc:gpu: [drm:drm_fb_helper_fbdev_setup 
>> [drm_kms_helper]] *ERROR* Failed to set fbdev configuration
>> [   10.404937] Unable to handle kernel paging request at virtual 
>> address 00330a656369768a
>> [   10.441620] [00330a656369768a] address between user and kernel 
>> address ranges
>> [   10.449087] Internal error: Oops: 96000004 [#1] PREEMPT SMP
>> [   10.454762] Modules linked in: brcmfmac vc4 drm_kms_helper 
>> cfg80211 drm rfkill smsc95xx brcmutil usbnet 
>> drm_panel_orientation_quirks raspberrypi_hwmon bcm2835_dma crc32_ce 
>> pwm_bcm2835 bcm2835_rng virt_dma rng_core i2c_bcm2835 ip_tables 
>> x_tables ipv6
>> [   10.477296] CPU: 2 PID: 45 Comm: kworker/2:1 Not tainted 
>> 4.19.0-rc5 #3
>> [   10.483934] Hardware name: Raspberry Pi 3 Model B Rev 1.2 (DT)
>> [   10.489966] Workqueue: events output_poll_execute [drm_kms_helper]
>> [   10.596515] Process kworker/2:1 (pid: 45, stack limit = 
>> 0x000000007e8924dc)
>> [   10.603590] Call trace:
>> [   10.606259]  drm_client_dev_hotplug+0x5c/0xb0 [drm]
>> [   10.611303]  drm_kms_helper_hotplug_event+0x30/0x40 [drm_kms_helper]
>> [   10.617849]  output_poll_execute+0xc4/0x1e0 [drm_kms_helper]
>> [   10.623616]  process_one_work+0x1c8/0x318
>> [   10.627695]  worker_thread+0x48/0x428
>> [   10.631420]  kthread+0xf8/0x128
>> [   10.634615]  ret_from_fork+0x10/0x18
>> [   10.638255] Code: 54000220 f9401261 aa1303e0 b4000141 (f9400c21)
>> [   10.644456] ---[ end trace c75b4a4b0e141908 ]---
>>
>> The reason for this is that drm_fbdev_cma_init() removes the drm_client
>> when fbdev registration fails, but it doesn't remove the client from the
>> drm_device client list. So the client list now has a pointer that points
>> into the unknown and we have a 'use after free' situation.
>>
>> Split drm_client_new() into drm_client_init() and drm_client_add() to 
>> fix
>> removal in the error path.
>>
>> Fixes: 894a677f4b3e ("drm/cma-helper: Use the generic fbdev emulation")
>> Reported-by: Sergey Suloev <ssuloev@orpaltech.com>
>> Cc: Stefan Wahren <stefan.wahren@i2se.com>
>> Cc: Eric Anholt <eric@anholt.net>
>> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
>> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
>> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>> ---
>
> Applied to drm-misc-fixes, thanks for the review.
>
> Noralf.
>
>> Changes since version 2:
>> - Fix drm_client_new() ref in docs (Daniel)
>> - Expand drm_client_add() docs (Daniel)
>>
>> Changes since version 1:
>> - Split drm_client_new() instead of letting drm_client hang around 
>> (Daniel)
>>
>>   drivers/gpu/drm/drm_client.c        | 35 
>> ++++++++++++++++++++++++++---------
>>   drivers/gpu/drm/drm_fb_cma_helper.c |  4 +++-
>>   drivers/gpu/drm/drm_fb_helper.c     |  4 +++-
>>   include/drm/drm_client.h            |  5 +++--
>>   4 files changed, 35 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
>> index 17d9a64e885e..fc03d26fcacc 100644
>> --- a/drivers/gpu/drm/drm_client.c
>> +++ b/drivers/gpu/drm/drm_client.c
>> @@ -63,20 +63,21 @@ static void drm_client_close(struct 
>> drm_client_dev *client)
>>   EXPORT_SYMBOL(drm_client_close);
>>     /**
>> - * drm_client_new - Create a DRM client
>> + * drm_client_init - Initialise a DRM client
>>    * @dev: DRM device
>>    * @client: DRM client
>>    * @name: Client name
>>    * @funcs: DRM client functions (optional)
>>    *
>> + * This initialises the client and opens a &drm_file. Use 
>> drm_client_add() to complete the process.
>>    * The caller needs to hold a reference on @dev before calling this 
>> function.
>>    * The client is freed when the &drm_device is unregistered. See 
>> drm_client_release().
>>    *
>>    * Returns:
>>    * Zero on success or negative error code on failure.
>>    */
>> -int drm_client_new(struct drm_device *dev, struct drm_client_dev 
>> *client,
>> -           const char *name, const struct drm_client_funcs *funcs)
>> +int drm_client_init(struct drm_device *dev, struct drm_client_dev 
>> *client,
>> +            const char *name, const struct drm_client_funcs *funcs)
>>   {
>>       int ret;
>>   @@ -95,10 +96,6 @@ int drm_client_new(struct drm_device *dev, 
>> struct drm_client_dev *client,
>>       if (ret)
>>           goto err_put_module;
>>   -    mutex_lock(&dev->clientlist_mutex);
>> -    list_add(&client->list, &dev->clientlist);
>> -    mutex_unlock(&dev->clientlist_mutex);
>> -
>>       drm_dev_get(dev);
>>         return 0;
>> @@ -109,13 +106,33 @@ int drm_client_new(struct drm_device *dev, 
>> struct drm_client_dev *client,
>>         return ret;
>>   }
>> -EXPORT_SYMBOL(drm_client_new);
>> +EXPORT_SYMBOL(drm_client_init);
>> +
>> +/**
>> + * drm_client_add - Add client to the device list
>> + * @client: DRM client
>> + *
>> + * Add the client to the &drm_device client list to activate its 
>> callbacks.
>> + * @client must be initialized by a call to drm_client_init(). After
>> + * drm_client_add() it is no longer permissible to call 
>> drm_client_release()
>> + * directly (outside the unregister callback), instead cleanup will 
>> happen
>> + * automatically on driver unload.
>> + */
>> +void drm_client_add(struct drm_client_dev *client)
>> +{
>> +    struct drm_device *dev = client->dev;
>> +
>> +    mutex_lock(&dev->clientlist_mutex);
>> +    list_add(&client->list, &dev->clientlist);
>> +    mutex_unlock(&dev->clientlist_mutex);
>> +}
>> +EXPORT_SYMBOL(drm_client_add);
>>     /**
>>    * drm_client_release - Release DRM client resources
>>    * @client: DRM client
>>    *
>> - * Releases resources by closing the &drm_file that was opened by 
>> drm_client_new().
>> + * Releases resources by closing the &drm_file that was opened by 
>> drm_client_init().
>>    * It is called automatically if the &drm_client_funcs.unregister 
>> callback is _not_ set.
>>    *
>>    * This function should only be called from the unregister 
>> callback. An exception
>> diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c 
>> b/drivers/gpu/drm/drm_fb_cma_helper.c
>> index 47e0e2f6642d..fb0dfc62b1b6 100644
>> --- a/drivers/gpu/drm/drm_fb_cma_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
>> @@ -167,7 +167,7 @@ struct drm_fbdev_cma *drm_fbdev_cma_init(struct 
>> drm_device *dev,
>>         fb_helper = &fbdev_cma->fb_helper;
>>   -    ret = drm_client_new(dev, &fb_helper->client, "fbdev", NULL);
>> +    ret = drm_client_init(dev, &fb_helper->client, "fbdev", NULL);
>>       if (ret)
>>           goto err_free;
>>   @@ -176,6 +176,8 @@ struct drm_fbdev_cma *drm_fbdev_cma_init(struct 
>> drm_device *dev,
>>       if (ret)
>>           goto err_client_put;
>>   +    drm_client_add(&fb_helper->client);
>> +
>>       return fbdev_cma;
>>     err_client_put:
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c 
>> b/drivers/gpu/drm/drm_fb_helper.c
>> index a504a5e05676..e9095537e0c0 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -3229,13 +3229,15 @@ int drm_fbdev_generic_setup(struct drm_device 
>> *dev, unsigned int preferred_bpp)
>>       if (!fb_helper)
>>           return -ENOMEM;
>>   -    ret = drm_client_new(dev, &fb_helper->client, "fbdev", 
>> &drm_fbdev_client_funcs);
>> +    ret = drm_client_init(dev, &fb_helper->client, "fbdev", 
>> &drm_fbdev_client_funcs);
>>       if (ret) {
>>           kfree(fb_helper);
>>           DRM_DEV_ERROR(dev->dev, "Failed to register client: %d\n", 
>> ret);
>>           return ret;
>>       }
>>   +    drm_client_add(&fb_helper->client);
>> +
>>       fb_helper->preferred_bpp = preferred_bpp;
>>         ret = drm_fbdev_client_hotplug(&fb_helper->client);
>> diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
>> index 989f8e52864d..971bb7853776 100644
>> --- a/include/drm/drm_client.h
>> +++ b/include/drm/drm_client.h
>> @@ -87,9 +87,10 @@ struct drm_client_dev {
>>       struct drm_file *file;
>>   };
>>   -int drm_client_new(struct drm_device *dev, struct drm_client_dev 
>> *client,
>> -           const char *name, const struct drm_client_funcs *funcs);
>> +int drm_client_init(struct drm_device *dev, struct drm_client_dev 
>> *client,
>> +            const char *name, const struct drm_client_funcs *funcs);
>>   void drm_client_release(struct drm_client_dev *client);
>> +void drm_client_add(struct drm_client_dev *client);
>>     void drm_client_dev_unregister(struct drm_device *dev);
>>   void drm_client_dev_hotplug(struct drm_device *dev);
>
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Re: [PATCH v3] drm/cma-helper: Fix crash in fbdev error path

[Sergey Suloev]

To be exact, the issue does not happen in case I use default kernel 
config but only with the custom one.


On 10/2/18 2:14 PM, Noralf Trønnes wrote:
>
> Den 01.10.2018 21.45, skrev Noralf Trønnes:
>> Sergey Suloev reported a crash happening in drm_client_dev_hotplug()
>> when fbdev had failed to register.
>>
>> [    9.124598] vc4_hdmi 3f902000.hdmi: ASoC: Failed to create 
>> component debugfs directory
>> [    9.147667] vc4_hdmi 3f902000.hdmi: vc4-hdmi-hifi <-> 
>> 3f902000.hdmi mapping ok
>> [    9.155184] vc4_hdmi 3f902000.hdmi: ASoC: no DMI vendor name!
>> [    9.166544] vc4-drm soc:gpu: bound 3f902000.hdmi (ops vc4_hdmi_ops 
>> [vc4])
>> [    9.173840] vc4-drm soc:gpu: bound 3f806000.vec (ops vc4_vec_ops 
>> [vc4])
>> [    9.181029] vc4-drm soc:gpu: bound 3f004000.txp (ops vc4_txp_ops 
>> [vc4])
>> [    9.188519] vc4-drm soc:gpu: bound 3f400000.hvs (ops vc4_hvs_ops 
>> [vc4])
>> [    9.195690] vc4-drm soc:gpu: bound 3f206000.pixelvalve (ops 
>> vc4_crtc_ops [vc4])
>> [    9.203523] vc4-drm soc:gpu: bound 3f207000.pixelvalve (ops 
>> vc4_crtc_ops [vc4])
>> [    9.215032] vc4-drm soc:gpu: bound 3f807000.pixelvalve (ops 
>> vc4_crtc_ops [vc4])
>> [    9.274785] vc4-drm soc:gpu: bound 3fc00000.v3d (ops vc4_v3d_ops 
>> [vc4])
>> [    9.290246] [drm] Initialized vc4 0.0.0 20140616 for soc:gpu on 
>> minor 0
>> [    9.297464] [drm] Supports vblank timestamp caching Rev 2 
>> (21.10.2013).
>> [    9.304600] [drm] Driver supports precise vblank timestamp query.
>> [    9.382856] vc4-drm soc:gpu: [drm:drm_fb_helper_fbdev_setup 
>> [drm_kms_helper]] *ERROR* Failed to set fbdev configuration
>> [   10.404937] Unable to handle kernel paging request at virtual 
>> address 00330a656369768a
>> [   10.441620] [00330a656369768a] address between user and kernel 
>> address ranges
>> [   10.449087] Internal error: Oops: 96000004 [#1] PREEMPT SMP
>> [   10.454762] Modules linked in: brcmfmac vc4 drm_kms_helper 
>> cfg80211 drm rfkill smsc95xx brcmutil usbnet 
>> drm_panel_orientation_quirks raspberrypi_hwmon bcm2835_dma crc32_ce 
>> pwm_bcm2835 bcm2835_rng virt_dma rng_core i2c_bcm2835 ip_tables 
>> x_tables ipv6
>> [   10.477296] CPU: 2 PID: 45 Comm: kworker/2:1 Not tainted 
>> 4.19.0-rc5 #3
>> [   10.483934] Hardware name: Raspberry Pi 3 Model B Rev 1.2 (DT)
>> [   10.489966] Workqueue: events output_poll_execute [drm_kms_helper]
>> [   10.596515] Process kworker/2:1 (pid: 45, stack limit = 
>> 0x000000007e8924dc)
>> [   10.603590] Call trace:
>> [   10.606259]  drm_client_dev_hotplug+0x5c/0xb0 [drm]
>> [   10.611303]  drm_kms_helper_hotplug_event+0x30/0x40 [drm_kms_helper]
>> [   10.617849]  output_poll_execute+0xc4/0x1e0 [drm_kms_helper]
>> [   10.623616]  process_one_work+0x1c8/0x318
>> [   10.627695]  worker_thread+0x48/0x428
>> [   10.631420]  kthread+0xf8/0x128
>> [   10.634615]  ret_from_fork+0x10/0x18
>> [   10.638255] Code: 54000220 f9401261 aa1303e0 b4000141 (f9400c21)
>> [   10.644456] ---[ end trace c75b4a4b0e141908 ]---
>>
>> The reason for this is that drm_fbdev_cma_init() removes the drm_client
>> when fbdev registration fails, but it doesn't remove the client from the
>> drm_device client list. So the client list now has a pointer that points
>> into the unknown and we have a 'use after free' situation.
>>
>> Split drm_client_new() into drm_client_init() and drm_client_add() to 
>> fix
>> removal in the error path.
>>
>> Fixes: 894a677f4b3e ("drm/cma-helper: Use the generic fbdev emulation")
>> Reported-by: Sergey Suloev <ssuloev@orpaltech.com>
>> Cc: Stefan Wahren <stefan.wahren@i2se.com>
>> Cc: Eric Anholt <eric@anholt.net>
>> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
>> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
>> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>> ---
>
> Applied to drm-misc-fixes, thanks for the review.
>
> Noralf.
>
>> Changes since version 2:
>> - Fix drm_client_new() ref in docs (Daniel)
>> - Expand drm_client_add() docs (Daniel)
>>
>> Changes since version 1:
>> - Split drm_client_new() instead of letting drm_client hang around 
>> (Daniel)
>>
>>   drivers/gpu/drm/drm_client.c        | 35 
>> ++++++++++++++++++++++++++---------
>>   drivers/gpu/drm/drm_fb_cma_helper.c |  4 +++-
>>   drivers/gpu/drm/drm_fb_helper.c     |  4 +++-
>>   include/drm/drm_client.h            |  5 +++--
>>   4 files changed, 35 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
>> index 17d9a64e885e..fc03d26fcacc 100644
>> --- a/drivers/gpu/drm/drm_client.c
>> +++ b/drivers/gpu/drm/drm_client.c
>> @@ -63,20 +63,21 @@ static void drm_client_close(struct 
>> drm_client_dev *client)
>>   EXPORT_SYMBOL(drm_client_close);
>>     /**
>> - * drm_client_new - Create a DRM client
>> + * drm_client_init - Initialise a DRM client
>>    * @dev: DRM device
>>    * @client: DRM client
>>    * @name: Client name
>>    * @funcs: DRM client functions (optional)
>>    *
>> + * This initialises the client and opens a &drm_file. Use 
>> drm_client_add() to complete the process.
>>    * The caller needs to hold a reference on @dev before calling this 
>> function.
>>    * The client is freed when the &drm_device is unregistered. See 
>> drm_client_release().
>>    *
>>    * Returns:
>>    * Zero on success or negative error code on failure.
>>    */
>> -int drm_client_new(struct drm_device *dev, struct drm_client_dev 
>> *client,
>> -           const char *name, const struct drm_client_funcs *funcs)
>> +int drm_client_init(struct drm_device *dev, struct drm_client_dev 
>> *client,
>> +            const char *name, const struct drm_client_funcs *funcs)
>>   {
>>       int ret;
>>   @@ -95,10 +96,6 @@ int drm_client_new(struct drm_device *dev, 
>> struct drm_client_dev *client,
>>       if (ret)
>>           goto err_put_module;
>>   -    mutex_lock(&dev->clientlist_mutex);
>> -    list_add(&client->list, &dev->clientlist);
>> -    mutex_unlock(&dev->clientlist_mutex);
>> -
>>       drm_dev_get(dev);
>>         return 0;
>> @@ -109,13 +106,33 @@ int drm_client_new(struct drm_device *dev, 
>> struct drm_client_dev *client,
>>         return ret;
>>   }
>> -EXPORT_SYMBOL(drm_client_new);
>> +EXPORT_SYMBOL(drm_client_init);
>> +
>> +/**
>> + * drm_client_add - Add client to the device list
>> + * @client: DRM client
>> + *
>> + * Add the client to the &drm_device client list to activate its 
>> callbacks.
>> + * @client must be initialized by a call to drm_client_init(). After
>> + * drm_client_add() it is no longer permissible to call 
>> drm_client_release()
>> + * directly (outside the unregister callback), instead cleanup will 
>> happen
>> + * automatically on driver unload.
>> + */
>> +void drm_client_add(struct drm_client_dev *client)
>> +{
>> +    struct drm_device *dev = client->dev;
>> +
>> +    mutex_lock(&dev->clientlist_mutex);
>> +    list_add(&client->list, &dev->clientlist);
>> +    mutex_unlock(&dev->clientlist_mutex);
>> +}
>> +EXPORT_SYMBOL(drm_client_add);
>>     /**
>>    * drm_client_release - Release DRM client resources
>>    * @client: DRM client
>>    *
>> - * Releases resources by closing the &drm_file that was opened by 
>> drm_client_new().
>> + * Releases resources by closing the &drm_file that was opened by 
>> drm_client_init().
>>    * It is called automatically if the &drm_client_funcs.unregister 
>> callback is _not_ set.
>>    *
>>    * This function should only be called from the unregister 
>> callback. An exception
>> diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c 
>> b/drivers/gpu/drm/drm_fb_cma_helper.c
>> index 47e0e2f6642d..fb0dfc62b1b6 100644
>> --- a/drivers/gpu/drm/drm_fb_cma_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
>> @@ -167,7 +167,7 @@ struct drm_fbdev_cma *drm_fbdev_cma_init(struct 
>> drm_device *dev,
>>         fb_helper = &fbdev_cma->fb_helper;
>>   -    ret = drm_client_new(dev, &fb_helper->client, "fbdev", NULL);
>> +    ret = drm_client_init(dev, &fb_helper->client, "fbdev", NULL);
>>       if (ret)
>>           goto err_free;
>>   @@ -176,6 +176,8 @@ struct drm_fbdev_cma *drm_fbdev_cma_init(struct 
>> drm_device *dev,
>>       if (ret)
>>           goto err_client_put;
>>   +    drm_client_add(&fb_helper->client);
>> +
>>       return fbdev_cma;
>>     err_client_put:
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c 
>> b/drivers/gpu/drm/drm_fb_helper.c
>> index a504a5e05676..e9095537e0c0 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -3229,13 +3229,15 @@ int drm_fbdev_generic_setup(struct drm_device 
>> *dev, unsigned int preferred_bpp)
>>       if (!fb_helper)
>>           return -ENOMEM;
>>   -    ret = drm_client_new(dev, &fb_helper->client, "fbdev", 
>> &drm_fbdev_client_funcs);
>> +    ret = drm_client_init(dev, &fb_helper->client, "fbdev", 
>> &drm_fbdev_client_funcs);
>>       if (ret) {
>>           kfree(fb_helper);
>>           DRM_DEV_ERROR(dev->dev, "Failed to register client: %d\n", 
>> ret);
>>           return ret;
>>       }
>>   +    drm_client_add(&fb_helper->client);
>> +
>>       fb_helper->preferred_bpp = preferred_bpp;
>>         ret = drm_fbdev_client_hotplug(&fb_helper->client);
>> diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
>> index 989f8e52864d..971bb7853776 100644
>> --- a/include/drm/drm_client.h
>> +++ b/include/drm/drm_client.h
>> @@ -87,9 +87,10 @@ struct drm_client_dev {
>>       struct drm_file *file;
>>   };
>>   -int drm_client_new(struct drm_device *dev, struct drm_client_dev 
>> *client,
>> -           const char *name, const struct drm_client_funcs *funcs);
>> +int drm_client_init(struct drm_device *dev, struct drm_client_dev 
>> *client,
>> +            const char *name, const struct drm_client_funcs *funcs);
>>   void drm_client_release(struct drm_client_dev *client);
>> +void drm_client_add(struct drm_client_dev *client);
>>     void drm_client_dev_unregister(struct drm_device *dev);
>>   void drm_client_dev_hotplug(struct drm_device *dev);
>
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Re: [PATCH v3] drm/cma-helper: Fix crash in fbdev error path

[Daniel Vetter]

On Sun, Nov 04, 2018 at 08:10:57PM +0300, Sergey Suloev wrote:
> To be exact, the issue does not happen in case I use default kernel config
> but only with the custom one.

Can you pls grab a new backtrace on latest kernels?

Thanks, Daniel

> 
> 
> On 10/2/18 2:14 PM, Noralf Trønnes wrote:
> > 
> > Den 01.10.2018 21.45, skrev Noralf Trønnes:
> > > Sergey Suloev reported a crash happening in drm_client_dev_hotplug()
> > > when fbdev had failed to register.
> > > 
> > > [    9.124598] vc4_hdmi 3f902000.hdmi: ASoC: Failed to create
> > > component debugfs directory
> > > [    9.147667] vc4_hdmi 3f902000.hdmi: vc4-hdmi-hifi <->
> > > 3f902000.hdmi mapping ok
> > > [    9.155184] vc4_hdmi 3f902000.hdmi: ASoC: no DMI vendor name!
> > > [    9.166544] vc4-drm soc:gpu: bound 3f902000.hdmi (ops
> > > vc4_hdmi_ops [vc4])
> > > [    9.173840] vc4-drm soc:gpu: bound 3f806000.vec (ops vc4_vec_ops
> > > [vc4])
> > > [    9.181029] vc4-drm soc:gpu: bound 3f004000.txp (ops vc4_txp_ops
> > > [vc4])
> > > [    9.188519] vc4-drm soc:gpu: bound 3f400000.hvs (ops vc4_hvs_ops
> > > [vc4])
> > > [    9.195690] vc4-drm soc:gpu: bound 3f206000.pixelvalve (ops
> > > vc4_crtc_ops [vc4])
> > > [    9.203523] vc4-drm soc:gpu: bound 3f207000.pixelvalve (ops
> > > vc4_crtc_ops [vc4])
> > > [    9.215032] vc4-drm soc:gpu: bound 3f807000.pixelvalve (ops
> > > vc4_crtc_ops [vc4])
> > > [    9.274785] vc4-drm soc:gpu: bound 3fc00000.v3d (ops vc4_v3d_ops
> > > [vc4])
> > > [    9.290246] [drm] Initialized vc4 0.0.0 20140616 for soc:gpu on
> > > minor 0
> > > [    9.297464] [drm] Supports vblank timestamp caching Rev 2
> > > (21.10.2013).
> > > [    9.304600] [drm] Driver supports precise vblank timestamp query.
> > > [    9.382856] vc4-drm soc:gpu: [drm:drm_fb_helper_fbdev_setup
> > > [drm_kms_helper]] *ERROR* Failed to set fbdev configuration
> > > [   10.404937] Unable to handle kernel paging request at virtual
> > > address 00330a656369768a
> > > [   10.441620] [00330a656369768a] address between user and kernel
> > > address ranges
> > > [   10.449087] Internal error: Oops: 96000004 [#1] PREEMPT SMP
> > > [   10.454762] Modules linked in: brcmfmac vc4 drm_kms_helper
> > > cfg80211 drm rfkill smsc95xx brcmutil usbnet
> > > drm_panel_orientation_quirks raspberrypi_hwmon bcm2835_dma crc32_ce
> > > pwm_bcm2835 bcm2835_rng virt_dma rng_core i2c_bcm2835 ip_tables
> > > x_tables ipv6
> > > [   10.477296] CPU: 2 PID: 45 Comm: kworker/2:1 Not tainted
> > > 4.19.0-rc5 #3
> > > [   10.483934] Hardware name: Raspberry Pi 3 Model B Rev 1.2 (DT)
> > > [   10.489966] Workqueue: events output_poll_execute [drm_kms_helper]
> > > [   10.596515] Process kworker/2:1 (pid: 45, stack limit =
> > > 0x000000007e8924dc)
> > > [   10.603590] Call trace:
> > > [   10.606259]  drm_client_dev_hotplug+0x5c/0xb0 [drm]
> > > [   10.611303]  drm_kms_helper_hotplug_event+0x30/0x40 [drm_kms_helper]
> > > [   10.617849]  output_poll_execute+0xc4/0x1e0 [drm_kms_helper]
> > > [   10.623616]  process_one_work+0x1c8/0x318
> > > [   10.627695]  worker_thread+0x48/0x428
> > > [   10.631420]  kthread+0xf8/0x128
> > > [   10.634615]  ret_from_fork+0x10/0x18
> > > [   10.638255] Code: 54000220 f9401261 aa1303e0 b4000141 (f9400c21)
> > > [   10.644456] ---[ end trace c75b4a4b0e141908 ]---
> > > 
> > > The reason for this is that drm_fbdev_cma_init() removes the drm_client
> > > when fbdev registration fails, but it doesn't remove the client from the
> > > drm_device client list. So the client list now has a pointer that points
> > > into the unknown and we have a 'use after free' situation.
> > > 
> > > Split drm_client_new() into drm_client_init() and drm_client_add()
> > > to fix
> > > removal in the error path.
> > > 
> > > Fixes: 894a677f4b3e ("drm/cma-helper: Use the generic fbdev emulation")
> > > Reported-by: Sergey Suloev <ssuloev@orpaltech.com>
> > > Cc: Stefan Wahren <stefan.wahren@i2se.com>
> > > Cc: Eric Anholt <eric@anholt.net>
> > > Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> > > Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> > > Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> > > ---
> > 
> > Applied to drm-misc-fixes, thanks for the review.
> > 
> > Noralf.
> > 
> > > Changes since version 2:
> > > - Fix drm_client_new() ref in docs (Daniel)
> > > - Expand drm_client_add() docs (Daniel)
> > > 
> > > Changes since version 1:
> > > - Split drm_client_new() instead of letting drm_client hang around
> > > (Daniel)
> > > 
> > >   drivers/gpu/drm/drm_client.c        | 35
> > > ++++++++++++++++++++++++++---------
> > >   drivers/gpu/drm/drm_fb_cma_helper.c |  4 +++-
> > >   drivers/gpu/drm/drm_fb_helper.c     |  4 +++-
> > >   include/drm/drm_client.h            |  5 +++--
> > >   4 files changed, 35 insertions(+), 13 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
> > > index 17d9a64e885e..fc03d26fcacc 100644
> > > --- a/drivers/gpu/drm/drm_client.c
> > > +++ b/drivers/gpu/drm/drm_client.c
> > > @@ -63,20 +63,21 @@ static void drm_client_close(struct
> > > drm_client_dev *client)
> > >   EXPORT_SYMBOL(drm_client_close);
> > >     /**
> > > - * drm_client_new - Create a DRM client
> > > + * drm_client_init - Initialise a DRM client
> > >    * @dev: DRM device
> > >    * @client: DRM client
> > >    * @name: Client name
> > >    * @funcs: DRM client functions (optional)
> > >    *
> > > + * This initialises the client and opens a &drm_file. Use
> > > drm_client_add() to complete the process.
> > >    * The caller needs to hold a reference on @dev before calling
> > > this function.
> > >    * The client is freed when the &drm_device is unregistered. See
> > > drm_client_release().
> > >    *
> > >    * Returns:
> > >    * Zero on success or negative error code on failure.
> > >    */
> > > -int drm_client_new(struct drm_device *dev, struct drm_client_dev
> > > *client,
> > > -           const char *name, const struct drm_client_funcs *funcs)
> > > +int drm_client_init(struct drm_device *dev, struct drm_client_dev
> > > *client,
> > > +            const char *name, const struct drm_client_funcs *funcs)
> > >   {
> > >       int ret;
> > >   @@ -95,10 +96,6 @@ int drm_client_new(struct drm_device *dev,
> > > struct drm_client_dev *client,
> > >       if (ret)
> > >           goto err_put_module;
> > >   -    mutex_lock(&dev->clientlist_mutex);
> > > -    list_add(&client->list, &dev->clientlist);
> > > -    mutex_unlock(&dev->clientlist_mutex);
> > > -
> > >       drm_dev_get(dev);
> > >         return 0;
> > > @@ -109,13 +106,33 @@ int drm_client_new(struct drm_device *dev,
> > > struct drm_client_dev *client,
> > >         return ret;
> > >   }
> > > -EXPORT_SYMBOL(drm_client_new);
> > > +EXPORT_SYMBOL(drm_client_init);
> > > +
> > > +/**
> > > + * drm_client_add - Add client to the device list
> > > + * @client: DRM client
> > > + *
> > > + * Add the client to the &drm_device client list to activate its
> > > callbacks.
> > > + * @client must be initialized by a call to drm_client_init(). After
> > > + * drm_client_add() it is no longer permissible to call
> > > drm_client_release()
> > > + * directly (outside the unregister callback), instead cleanup will
> > > happen
> > > + * automatically on driver unload.
> > > + */
> > > +void drm_client_add(struct drm_client_dev *client)
> > > +{
> > > +    struct drm_device *dev = client->dev;
> > > +
> > > +    mutex_lock(&dev->clientlist_mutex);
> > > +    list_add(&client->list, &dev->clientlist);
> > > +    mutex_unlock(&dev->clientlist_mutex);
> > > +}
> > > +EXPORT_SYMBOL(drm_client_add);
> > >     /**
> > >    * drm_client_release - Release DRM client resources
> > >    * @client: DRM client
> > >    *
> > > - * Releases resources by closing the &drm_file that was opened by
> > > drm_client_new().
> > > + * Releases resources by closing the &drm_file that was opened by
> > > drm_client_init().
> > >    * It is called automatically if the &drm_client_funcs.unregister
> > > callback is _not_ set.
> > >    *
> > >    * This function should only be called from the unregister
> > > callback. An exception
> > > diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c
> > > b/drivers/gpu/drm/drm_fb_cma_helper.c
> > > index 47e0e2f6642d..fb0dfc62b1b6 100644
> > > --- a/drivers/gpu/drm/drm_fb_cma_helper.c
> > > +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
> > > @@ -167,7 +167,7 @@ struct drm_fbdev_cma *drm_fbdev_cma_init(struct
> > > drm_device *dev,
> > >         fb_helper = &fbdev_cma->fb_helper;
> > >   -    ret = drm_client_new(dev, &fb_helper->client, "fbdev", NULL);
> > > +    ret = drm_client_init(dev, &fb_helper->client, "fbdev", NULL);
> > >       if (ret)
> > >           goto err_free;
> > >   @@ -176,6 +176,8 @@ struct drm_fbdev_cma
> > > *drm_fbdev_cma_init(struct drm_device *dev,
> > >       if (ret)
> > >           goto err_client_put;
> > >   +    drm_client_add(&fb_helper->client);
> > > +
> > >       return fbdev_cma;
> > >     err_client_put:
> > > diff --git a/drivers/gpu/drm/drm_fb_helper.c
> > > b/drivers/gpu/drm/drm_fb_helper.c
> > > index a504a5e05676..e9095537e0c0 100644
> > > --- a/drivers/gpu/drm/drm_fb_helper.c
> > > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > > @@ -3229,13 +3229,15 @@ int drm_fbdev_generic_setup(struct
> > > drm_device *dev, unsigned int preferred_bpp)
> > >       if (!fb_helper)
> > >           return -ENOMEM;
> > >   -    ret = drm_client_new(dev, &fb_helper->client, "fbdev",
> > > &drm_fbdev_client_funcs);
> > > +    ret = drm_client_init(dev, &fb_helper->client, "fbdev",
> > > &drm_fbdev_client_funcs);
> > >       if (ret) {
> > >           kfree(fb_helper);
> > >           DRM_DEV_ERROR(dev->dev, "Failed to register client: %d\n",
> > > ret);
> > >           return ret;
> > >       }
> > >   +    drm_client_add(&fb_helper->client);
> > > +
> > >       fb_helper->preferred_bpp = preferred_bpp;
> > >         ret = drm_fbdev_client_hotplug(&fb_helper->client);
> > > diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
> > > index 989f8e52864d..971bb7853776 100644
> > > --- a/include/drm/drm_client.h
> > > +++ b/include/drm/drm_client.h
> > > @@ -87,9 +87,10 @@ struct drm_client_dev {
> > >       struct drm_file *file;
> > >   };
> > >   -int drm_client_new(struct drm_device *dev, struct drm_client_dev
> > > *client,
> > > -           const char *name, const struct drm_client_funcs *funcs);
> > > +int drm_client_init(struct drm_device *dev, struct drm_client_dev
> > > *client,
> > > +            const char *name, const struct drm_client_funcs *funcs);
> > >   void drm_client_release(struct drm_client_dev *client);
> > > +void drm_client_add(struct drm_client_dev *client);
> > >     void drm_client_dev_unregister(struct drm_device *dev);
> > >   void drm_client_dev_hotplug(struct drm_device *dev);
> > 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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