[PATCH 2/2] media: protect enable and disable source handler checks and calls

[Shuah Khan]

Protect enable and disable source handler checks and calls from dvb-core
and v4l2-core. Hold graph_mutex to check if enable and disable source
handlers are present and invoke them while holding the mutex. This change
ensures these handlers will not be removed while they are being checked
and invoked.

au08282 enable and disable source handlers are changed to not hold the
graph_mutex.

Signed-off-by: Shuah Khan <shuahkh@xxxxxxxxxxxxxxx>
---
 drivers/media/dvb-core/dvb_frontend.c  | 24 ++++++++++++++++++------
 drivers/media/usb/au0828/au0828-core.c | 17 +++++------------
 drivers/media/v4l2-core/v4l2-mc.c      | 26 ++++++++++++++++++--------
 3 files changed, 41 insertions(+), 26 deletions(-)

diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
index 01511e5..2f09c7e 100644
--- a/drivers/media/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb-core/dvb_frontend.c
@@ -2527,9 +2527,13 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
 		fepriv->voltage = -1;
 
 #ifdef CONFIG_MEDIA_CONTROLLER_DVB
-		if (fe->dvb->mdev && fe->dvb->mdev->enable_source) {
-			ret = fe->dvb->mdev->enable_source(dvbdev->entity,
+		if (fe->dvb->mdev) {
+			mutex_lock(&fe->dvb->mdev->graph_mutex);
+			if (fe->dvb->mdev->enable_source)
+				ret = fe->dvb->mdev->enable_source(
+							   dvbdev->entity,
 							   &fepriv->pipe);
+			mutex_unlock(&fe->dvb->mdev->graph_mutex);
 			if (ret) {
 				dev_err(fe->dvb->device,
 					"Tuner is busy. Error %d\n", ret);
@@ -2553,8 +2557,12 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
 
 err3:
 #ifdef CONFIG_MEDIA_CONTROLLER_DVB
-	if (fe->dvb->mdev && fe->dvb->mdev->disable_source)
-		fe->dvb->mdev->disable_source(dvbdev->entity);
+	if (fe->dvb->mdev) {
+		mutex_lock(&fe->dvb->mdev->graph_mutex);
+		if (fe->dvb->mdev->disable_source)
+			fe->dvb->mdev->disable_source(dvbdev->entity);
+		mutex_unlock(&fe->dvb->mdev->graph_mutex);
+	}
 err2:
 #endif
 	dvb_generic_release(inode, file);
@@ -2586,8 +2594,12 @@ static int dvb_frontend_release(struct inode *inode, struct file *file)
 	if (dvbdev->users == -1) {
 		wake_up(&fepriv->wait_queue);
 #ifdef CONFIG_MEDIA_CONTROLLER_DVB
-		if (fe->dvb->mdev && fe->dvb->mdev->disable_source)
-			fe->dvb->mdev->disable_source(dvbdev->entity);
+		if (fe->dvb->mdev) {
+			mutex_lock(&fe->dvb->mdev->graph_mutex);
+			if (fe->dvb->mdev->disable_source)
+				fe->dvb->mdev->disable_source(dvbdev->entity);
+			mutex_unlock(&fe->dvb->mdev->graph_mutex);
+		}
 #endif
 		if (fe->exit != DVB_FE_NO_EXIT)
 			wake_up(&dvbdev->wait_queue);
diff --git a/drivers/media/usb/au0828/au0828-core.c b/drivers/media/usb/au0828/au0828-core.c
index a1f696a..bfd6482 100644
--- a/drivers/media/usb/au0828/au0828-core.c
+++ b/drivers/media/usb/au0828/au0828-core.c
@@ -280,6 +280,7 @@ static void au0828_media_graph_notify(struct media_entity *new,
 	}
 }
 
+/* Callers should hold graph_mutex */
 static int au0828_enable_source(struct media_entity *entity,
 				struct media_pipeline *pipe)
 {
@@ -293,8 +294,6 @@ static int au0828_enable_source(struct media_entity *entity,
 	if (!mdev)
 		return -ENODEV;
 
-	mutex_lock(&mdev->graph_mutex);
-
 	dev = mdev->source_priv;
 
 	/*
@@ -421,12 +420,12 @@ static int au0828_enable_source(struct media_entity *entity,
 		 dev->active_source->name, dev->active_sink->name,
 		 dev->active_link_owner->name, ret);
 end:
-	mutex_unlock(&mdev->graph_mutex);
 	pr_debug("au0828_enable_source() end %s %d %d\n",
 		 entity->name, entity->function, ret);
 	return ret;
 }
 
+/* Callers should hold graph_mutex */
 static void au0828_disable_source(struct media_entity *entity)
 {
 	int ret = 0;
@@ -436,13 +435,10 @@ static void au0828_disable_source(struct media_entity *entity)
 	if (!mdev)
 		return;
 
-	mutex_lock(&mdev->graph_mutex);
 	dev = mdev->source_priv;
 
-	if (!dev->active_link) {
-		ret = -ENODEV;
-		goto end;
-	}
+	if (!dev->active_link)
+		return;
 
 	/* link is active - stop pipeline from source (tuner) */
 	if (dev->active_link->sink->entity == dev->active_sink &&
@@ -452,7 +448,7 @@ static void au0828_disable_source(struct media_entity *entity)
 		 * has active pipeline
 		*/
 		if (dev->active_link_owner != entity)
-			goto end;
+			return;
 		__media_entity_pipeline_stop(entity);
 		ret = __media_entity_setup_link(dev->active_link, 0);
 		if (ret)
@@ -467,9 +463,6 @@ static void au0828_disable_source(struct media_entity *entity)
 		dev->active_source = NULL;
 		dev->active_sink = NULL;
 	}
-
-end:
-	mutex_unlock(&mdev->graph_mutex);
 }
 #endif
 
diff --git a/drivers/media/v4l2-core/v4l2-mc.c b/drivers/media/v4l2-core/v4l2-mc.c
index 8bef433..b169d24 100644
--- a/drivers/media/v4l2-core/v4l2-mc.c
+++ b/drivers/media/v4l2-core/v4l2-mc.c
@@ -198,14 +198,20 @@ EXPORT_SYMBOL_GPL(v4l2_mc_create_media_graph);
 int v4l_enable_media_source(struct video_device *vdev)
 {
 	struct media_device *mdev = vdev->entity.graph_obj.mdev;
-	int ret;
+	int ret = 0, err;
 
-	if (!mdev || !mdev->enable_source)
+	if (!mdev)
 		return 0;
-	ret = mdev->enable_source(&vdev->entity, &vdev->pipe);
-	if (ret)
-		return -EBUSY;
-	return 0;
+
+	mutex_lock(&mdev->graph_mutex);
+	if (!mdev->enable_source)
+		goto end;
+	err = mdev->enable_source(&vdev->entity, &vdev->pipe);
+	if (err)
+		ret = -EBUSY;
+end:
+	mutex_unlock(&mdev->graph_mutex);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(v4l_enable_media_source);
 
@@ -213,8 +219,12 @@ void v4l_disable_media_source(struct video_device *vdev)
 {
 	struct media_device *mdev = vdev->entity.graph_obj.mdev;
 
-	if (mdev && mdev->disable_source)
-		mdev->disable_source(&vdev->entity);
+	if (mdev) {
+		mutex_lock(&mdev->graph_mutex);
+		if (mdev->disable_source)
+			mdev->disable_source(&vdev->entity);
+		mutex_unlock(&mdev->graph_mutex);
+	}
 }
 EXPORT_SYMBOL_GPL(v4l_disable_media_source);
 
-- 
2.7.4