[PATCH 1/1] Avoid usb reset crashes by making tty_io cdevs truly dynamic

[Richard Watts]

Avoid usb reset crashes by making tty_io cdevs truly dynamic

Signed-off-by: Richard Watts <rrw@xxxxxxxxxxxxx>
Reported-by: Duncan Mackintosh <DMackintosh@xxxxxxxx>
---
 drivers/tty/tty_io.c       | 24 ++++++++++++++++--------
 include/linux/tty_driver.h |  2 +-
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index e569546..699cf20 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3168,9 +3168,12 @@ static int tty_cdev_add(struct tty_driver 
*driver, dev_t dev,
 		unsigned int index, unsigned int count)
 {
 	/* init here, since reused cdevs cause crashes */
-	cdev_init(&driver->cdevs[index], &tty_fops);
-	driver->cdevs[index].owner = driver->owner;
-	return cdev_add(&driver->cdevs[index], dev, count);
+	driver->cdevs[index] = cdev_alloc();
+	if (!driver->cdevs[index])
+		return -ENOMEM;
+	cdev_init(driver->cdevs[index], &tty_fops);
+	driver->cdevs[index]->owner = driver->owner;
+	return cdev_add(driver->cdevs[index], dev, count);
 }

 /**
@@ -3276,8 +3279,10 @@ struct device *tty_register_device_attr(struct 
tty_driver *driver,

 error:
 	put_device(dev);
-	if (cdev)
-		cdev_del(&driver->cdevs[index]);
+	if (cdev) {
+		cdev_del(driver->cdevs[index]);
+		driver->cdevs[index] = NULL;
+	}
 	return ERR_PTR(retval);
 }
 EXPORT_SYMBOL_GPL(tty_register_device_attr);
@@ -3297,8 +3302,10 @@ void tty_unregister_device(struct tty_driver 
*driver, unsigned index)
 {
 	device_destroy(tty_class,
 		MKDEV(driver->major, driver->minor_start) + index);
-	if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC))
-		cdev_del(&driver->cdevs[index]);
+	if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
+		cdev_del(driver->cdevs[index]);
+		driver->cdevs[index] = NULL;
+	}
 }
 EXPORT_SYMBOL(tty_unregister_device);

@@ -3363,6 +3370,7 @@ err_free_all:
 	kfree(driver->ports);
 	kfree(driver->ttys);
 	kfree(driver->termios);
+	kfree(driver->cdevs);
 	kfree(driver);
 	return ERR_PTR(err);
 }
@@ -3391,7 +3399,7 @@ static void destruct_tty_driver(struct kref *kref)
 		}
 		proc_tty_unregister_driver(driver);
 		if (driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)
-			cdev_del(&driver->cdevs[0]);
+			cdev_del(driver->cdevs[0]);
 	}
 	kfree(driver->cdevs);
 	kfree(driver->ports);
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index 92e337c..1610524 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -296,7 +296,7 @@ struct tty_operations {
 struct tty_driver {
 	int	magic;		/* magic number for this structure */
 	struct kref kref;	/* Reference management */
-	struct cdev *cdevs;
+	struct cdev **cdevs;
 	struct module	*owner;
 	const char	*driver_name;
 	const char	*name;
--
1.9.1
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