Re: [patch] i2c: dev: use after free in detach

[Wolfram Sang <wsa@the-dreams.de>]

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On Sat, May 28, 2016 at 08:01:46AM +0300, Dan Carpenter wrote:
> The call to return_i2c_dev() frees "i2c_dev" so there is a use after
> free when we call cdev_del(&i2c_dev->cdev).
> 
> Fixes: d6760b14d4a1 ('i2c: dev: switch from register_chrdev to cdev API')
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Thanks! I'll revert the offending commit nonetheless because I still
want to understand first why it slipped through my test system. And then
we will try again with a better patch.

> 
> diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
> index 2562a45..3bf4f0d 100644
> --- a/drivers/i2c/i2c-dev.c
> +++ b/drivers/i2c/i2c-dev.c
> @@ -592,9 +592,9 @@ static int i2cdev_detach_adapter(struct device *dev, void *dummy)
>  	if (!i2c_dev) /* attach_adapter must have failed */
>  		return 0;
>  
> +	cdev_del(&i2c_dev->cdev);
>  	return_i2c_dev(i2c_dev);
>  	device_destroy(i2c_dev_class, MKDEV(I2C_MAJOR, adap->nr));
> -	cdev_del(&i2c_dev->cdev);
>  
>  	pr_debug("i2c-dev: adapter [%s] unregistered\n", adap->name);
>  	return 0;

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