Re: [PATCH 1/2] i2c-dev: don't get i2c adapter via i2c_dev

From	Jean Delvare <jdelvare@suse.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/2] i2c-dev: don't get i2c adapter via i2c_dev
Date	2016-07-07 15:20 +0200
Message-ID	<rShnH-7n8-9@gated-at.bofh.it> (permalink)
References	<rRLe9-3nf-3@gated-at.bofh.it> <rRLe9-3nf-1@gated-at.bofh.it>
Organization	SUSE Linux

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On Tue,  5 Jul 2016 19:57:06 -0700, Viresh Kumar wrote:
> There is no code protecting i2c_dev to be freed after it is returned
> from i2c_dev_get_by_minor() and using it to access the value which we
> already have (minor) isn't safe really.
> 
> Avoid using it and get the adapter directly from 'minor'.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
>  drivers/i2c/i2c-dev.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
> index 6ecfd76270f2..66f323fd3982 100644
> --- a/drivers/i2c/i2c-dev.c
> +++ b/drivers/i2c/i2c-dev.c
> @@ -485,13 +485,8 @@ static int i2cdev_open(struct inode *inode, struct file *file)
>  	unsigned int minor = iminor(inode);
>  	struct i2c_client *client;
>  	struct i2c_adapter *adap;
> -	struct i2c_dev *i2c_dev;
> -
> -	i2c_dev = i2c_dev_get_by_minor(minor);
> -	if (!i2c_dev)
> -		return -ENODEV;
>  
> -	adap = i2c_get_adapter(i2c_dev->adap->nr);
> +	adap = i2c_get_adapter(minor);
>  	if (!adap)
>  		return -ENODEV;
>  

Anyway, this is a good cleanup/optimization on its own, on top of
fixing a race condition, independently of what we decide for the rest
of the problems being discussed in this thread. So:

Reviewed-by: Jean Delvare <jdelvare@suse.de>
Tested-by: Jean Delvare <jdelvare@suse.de>

Thanks,
-- 
Jean Delvare
SUSE L3 Support

Thread

[PATCH 1/2] i2c-dev: don't get i2c adapter via i2c_dev Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-06 05:00 +0200
  Re: [PATCH 1/2] i2c-dev: don't get i2c adapter via i2c_dev Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-06 19:10 +0200
  Re: [PATCH 1/2] i2c-dev: don't get i2c adapter via i2c_dev Jean Delvare <jdelvare@suse.de> - 2016-07-06 19:10 +0200
  Re: [PATCH 1/2] i2c-dev: don't get i2c adapter via i2c_dev Jean Delvare <jdelvare@suse.de> - 2016-07-07 15:20 +0200
    Re: [PATCH 1/2] i2c-dev: don't get i2c adapter via i2c_dev Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-07 17:40 +0200
  Re: [PATCH 1/2] i2c-dev: don't get i2c adapter via i2c_dev Wolfram Sang <wsa@the-dreams.de> - 2016-07-08 03:40 +0200

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