TTY: move cdev_add to tty_register_device

We need the /dev/ node not to be available before we call
tty_register_device. Otherwise we might race with open and
tty_struct->port might not be available at that time.

This is not an issue now, but would be a problem after "TTY: use
tty_port_register_device" is applied.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 4d9898c2b641d8981c505d150f19db89b5313de9..28c3e869ebba722c5f30bc4675b127f60889684e 100644 (file)
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3006,6 +3006,15 @@ EXPORT_SYMBOL_GPL(tty_put_char);
 
 struct class *tty_class;
 
+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);
+}
+
 /**
  *     tty_register_device - register a tty device
  *     @driver: the tty driver that describes the tty device
@@ -3028,8 +3037,10 @@ struct class *tty_class;
 struct device *tty_register_device(struct tty_driver *driver, unsigned index,
                                   struct device *device)
 {
+       struct device *ret;
        char name[64];
        dev_t dev = MKDEV(driver->major, driver->minor_start) + index;
+       bool cdev = false;
 
        if (index >= driver->num) {
                printk(KERN_ERR "Attempt to register invalid tty line number "
@@ -3042,7 +3053,18 @@ struct device *tty_register_device(struct tty_driver *driver, unsigned index,
        else
                tty_line_name(driver, index, name);
 
-       return device_create(tty_class, device, dev, NULL, name);
+       if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
+               int error = tty_cdev_add(driver, dev, index, 1);
+               if (error)
+                       return ERR_PTR(error);
+               cdev = true;
+       }
+
+       ret = device_create(tty_class, device, dev, NULL, name);
+       if (IS_ERR(ret) && cdev)
+               cdev_del(&driver->cdevs[index]);
+
+       return ret;
 }
 EXPORT_SYMBOL(tty_register_device);
 
@@ -3061,6 +3083,8 @@ 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]);
 }
 EXPORT_SYMBOL(tty_unregister_device);
 
@@ -3077,6 +3101,7 @@ struct tty_driver *__tty_alloc_driver(unsigned int lines, struct module *owner,
                unsigned long flags)
 {
        struct tty_driver *driver;
+       unsigned int cdevs = 1;
        int err;
 
        if (!lines || (flags & TTY_DRIVER_UNNUMBERED_NODE && lines > 1))
@@ -3110,6 +3135,13 @@ struct tty_driver *__tty_alloc_driver(unsigned int lines, struct module *owner,
                        err = -ENOMEM;
                        goto err_free_all;
                }
+               cdevs = lines;
+       }
+
+       driver->cdevs = kcalloc(cdevs, sizeof(*driver->cdevs), GFP_KERNEL);
+       if (!driver->cdevs) {
+               err = -ENOMEM;
+               goto err_free_all;
        }
 
        return driver;
@@ -3144,8 +3176,10 @@ static void destruct_tty_driver(struct kref *kref)
                                tty_unregister_device(driver, i);
                }
                proc_tty_unregister_driver(driver);
-               cdev_del(&driver->cdev);
+               if (driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)
+                       cdev_del(&driver->cdevs[0]);
        }
+       kfree(driver->cdevs);
        kfree(driver->ports);
        kfree(driver->termios);
        kfree(driver->ttys);
@@ -3195,11 +3229,11 @@ int tty_register_driver(struct tty_driver *driver)
        if (error < 0)
                goto err;
 
-       cdev_init(&driver->cdev, &tty_fops);
-       driver->cdev.owner = driver->owner;
-       error = cdev_add(&driver->cdev, dev, driver->num);
-       if (error)
-               goto err_unreg_char;
+       if (driver->flags & TTY_DRIVER_DYNAMIC_ALLOC) {
+               error = tty_cdev_add(driver, dev, 0, driver->num);
+               if (error)
+                       goto err_unreg_char;
+       }
 
        mutex_lock(&tty_mutex);
        list_add(&driver->tty_drivers, &tty_drivers);

diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index 44e05b75d57347d42b1c6fafd2e1f0c1783acfcd..dd976cfb61312d66d53d6a9e009e70d3eb4d347d 100644 (file)
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -289,7 +289,7 @@ struct tty_operations {
 struct tty_driver {
        int     magic;          /* magic number for this structure */
        struct kref kref;       /* Reference management */
-       struct cdev cdev;
+       struct cdev *cdevs;
        struct module   *owner;
        const char      *driver_name;
        const char      *name;