Avoid usb reset crashes by making tty_io cdevs truly dynamic

Avoid usb reset crashes by making tty_io cdevs truly dynamic

Signed-off-by: Richard Watts <rrw@kynesim.co.uk>
Reported-by: Duncan Mackintosh <DMackintosh@cbnl.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 16 insertions, 8 deletions

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index c37a215177c0..02785d844354 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3152,9 +3152,12 @@ 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);
 }
 
 /**
@@ -3260,8 +3263,10 @@ 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);
@@ -3281,8 +3286,10 @@ 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);
 
@@ -3347,6 +3354,7 @@ err_free_all:
         kfree(driver->ports);
         kfree(driver->ttys);
         kfree(driver->termios);
+        kfree(driver->cdevs);
         kfree(driver);
         return ERR_PTR(err);
 }
@@ -3375,7 +3383,7 @@ 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);