[PATCH] tty: don't leak cdev in tty_cdev_add()

From: Leon Yu
Date: Mon Sep 07 2015 - 09:09:56 EST

Commit a3a10ce3429e ("Avoid usb reset crashes by making tty_io cdevs truly
dynamic") which mixes using cdev_alloc() and cdev_init() is problematic.
Subsequent call to cdev_init() after cdev_alloc() sets kobj release method
from cdev_dynamic_release() to cdev_default_release() and thus makes it
impossible to free allocated cdev.

This patch also consolidates error path of cdev_add() as cdev can also leak
here if things went wrong.

Signed-off-by: Leon Yu <chianglungyu@xxxxxxxxx>
Fixes: a3a10ce3429e ("Avoid usb reset crashes by making tty_io cdevs truly dynamic")
drivers/tty/tty_io.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 02785d8..17b0272 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3151,13 +3151,18 @@ struct class *tty_class;
static int tty_cdev_add(struct tty_driver *driver, dev_t dev,
unsigned int index, unsigned int count)
+ int err;
/* init here, since reused cdevs cause crashes */
driver->cdevs[index] = cdev_alloc();
if (!driver->cdevs[index])
return -ENOMEM;
- cdev_init(driver->cdevs[index], &tty_fops);
+ driver->cdevs[index]->ops = &tty_fops;
driver->cdevs[index]->owner = driver->owner;
- return cdev_add(driver->cdevs[index], dev, count);
+ err = cdev_add(driver->cdevs[index], dev, count);
+ if (err)
+ kobject_put(&driver->cdevs[index]->kobj);
+ return err;


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/