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Subject[PATCH v2 21/41] TTY: move cdev_add to tty_register_device
Date
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>
---
drivers/tty/tty_io.c | 48 +++++++++++++++++++++++++++++++++++++-------
include/linux/tty_driver.h | 2 +-
2 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 59a73af..f83d450 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2991,6 +2991,15 @@ 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
@@ -3013,8 +3022,10 @@ 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 "
@@ -3027,7 +3038,18 @@ 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);

@@ -3046,6 +3068,8 @@ 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);

@@ -3062,6 +3086,7 @@ 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))
@@ -3095,6 +3120,13 @@ 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;
@@ -3129,8 +3161,10 @@ 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);
@@ -3180,11 +3214,11 @@ 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 44e05b7..dd976cf 100644
--- 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;
--
1.7.10.4



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