Merge tag 'media/v6.4-6' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media

Pull media fixes from Mauro Carvalho Chehab:
 "A fix for dvb-core to avoid a race condition during DVB board
  registration"

* tag 'media/v6.4-6' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media:
  Revert "media: dvb-core: Fix use-after-free on race condition at dvb_frontend"

Author: torvalds

drivers/media/dvb-core/dvb_frontend.c

@@ -817,26 +817,15 @@ static void dvb_frontend_stop(struct dvb_frontend *fe)
 
 	dev_dbg(fe->dvb->device, "%s:\n", __func__);
 
-	mutex_lock(&fe->remove_mutex);
-
 	if (fe->exit != DVB_FE_DEVICE_REMOVED)
 		fe->exit = DVB_FE_NORMAL_EXIT;
 	mb();
 
-	if (!fepriv->thread) {
-		mutex_unlock(&fe->remove_mutex);
+	if (!fepriv->thread)
 		return;
-	}
 
 	kthread_stop(fepriv->thread);
 
-	mutex_unlock(&fe->remove_mutex);
-
-	if (fepriv->dvbdev->users < -1) {
-		wait_event(fepriv->dvbdev->wait_queue,
-			   fepriv->dvbdev->users == -1);
-	}
-
 	sema_init(&fepriv->sem, 1);
 	fepriv->state = FESTATE_IDLE;
 
@@ -2780,22 +2769,17 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
 	struct dvb_adapter *adapter = fe->dvb;
 	int ret;
 
-	mutex_lock(&fe->remove_mutex);
-
 	dev_dbg(fe->dvb->device, "%s:\n", __func__);
-	if (fe->exit == DVB_FE_DEVICE_REMOVED) {
-		ret = -ENODEV;
-		goto err_remove_mutex;
-	}
+	if (fe->exit == DVB_FE_DEVICE_REMOVED)
+		return -ENODEV;
 
 	if (adapter->mfe_shared == 2) {
 		mutex_lock(&adapter->mfe_lock);
 		if ((file->f_flags & O_ACCMODE) != O_RDONLY) {
 			if (adapter->mfe_dvbdev &&
 			    !adapter->mfe_dvbdev->writers) {
 				mutex_unlock(&adapter->mfe_lock);
-				ret = -EBUSY;
-				goto err_remove_mutex;
+				return -EBUSY;
 			}
 			adapter->mfe_dvbdev = dvbdev;
 		}
@@ -2818,10 +2802,8 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
 			while (mferetry-- && (mfedev->users != -1 ||
 					      mfepriv->thread)) {
 				if (msleep_interruptible(500)) {
-					if (signal_pending(current)) {
-						ret = -EINTR;
-						goto err_remove_mutex;
-					}
+					if (signal_pending(current))
+						return -EINTR;
 				}
 			}
 
@@ -2833,8 +2815,7 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
 				if (mfedev->users != -1 ||
 				    mfepriv->thread) {
 					mutex_unlock(&adapter->mfe_lock);
-					ret = -EBUSY;
-					goto err_remove_mutex;
+					return -EBUSY;
 				}
 				adapter->mfe_dvbdev = dvbdev;
 			}
@@ -2893,8 +2874,6 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
 
 	if (adapter->mfe_shared)
 		mutex_unlock(&adapter->mfe_lock);
-
-	mutex_unlock(&fe->remove_mutex);
 	return ret;
 
 err3:
@@ -2916,9 +2895,6 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
 err0:
 	if (adapter->mfe_shared)
 		mutex_unlock(&adapter->mfe_lock);
-
-err_remove_mutex:
-	mutex_unlock(&fe->remove_mutex);
 	return ret;
 }
 
@@ -2929,8 +2905,6 @@ static int dvb_frontend_release(struct inode *inode, struct file *file)
 	struct dvb_frontend_private *fepriv = fe->frontend_priv;
 	int ret;
 
-	mutex_lock(&fe->remove_mutex);
-
 	dev_dbg(fe->dvb->device, "%s:\n", __func__);
 
 	if ((file->f_flags & O_ACCMODE) != O_RDONLY) {
@@ -2952,18 +2926,10 @@ static int dvb_frontend_release(struct inode *inode, struct file *file)
 		}
 		mutex_unlock(&fe->dvb->mdev_lock);
 #endif
+		if (fe->exit != DVB_FE_NO_EXIT)
+			wake_up(&dvbdev->wait_queue);
 		if (fe->ops.ts_bus_ctrl)
 			fe->ops.ts_bus_ctrl(fe, 0);
-
-		if (fe->exit != DVB_FE_NO_EXIT) {
-			mutex_unlock(&fe->remove_mutex);
-			wake_up(&dvbdev->wait_queue);
-		} else {
-			mutex_unlock(&fe->remove_mutex);
-		}
-
-	} else {
-		mutex_unlock(&fe->remove_mutex);
 	}
 
 	dvb_frontend_put(fe);
@@ -3064,7 +3030,6 @@ int dvb_register_frontend(struct dvb_adapter *dvb,
 	fepriv = fe->frontend_priv;
 
 	kref_init(&fe->refcount);
-	mutex_init(&fe->remove_mutex);
 
 	/*
 	 * After initialization, there need to be two references: one

include/media/dvb_frontend.h

@@ -686,10 +686,7 @@ struct dtv_frontend_properties {
  * @id:			Frontend ID
  * @exit:		Used to inform the DVB core that the frontend
  *			thread should exit (usually, means that the hardware
- *			got disconnected).
- * @remove_mutex:	mutex that avoids a race condition between a callback
- *			called when the hardware is disconnected and the
- *			file_operations of dvb_frontend.
+ *			got disconnected.
  */
 
 struct dvb_frontend {
@@ -707,7 +704,6 @@ struct dvb_frontend {
 	int (*callback)(void *adapter_priv, int component, int cmd, int arg);
 	int id;
 	unsigned int exit;
-	struct mutex remove_mutex;
 };
 
 /**