Subject: Re: [PATCH net-next] sockopt: Make SO_BINDTODEVICE readable

From: Brian Haley <[email-masked]>
Date: Mon, 22 Oct 2012 17:20:48 -0400

On 10/22/2012 04:45 PM, Eric Dumazet wrote:
> On Mon, 2012-10-22 at 14:04 -0400, Brian Haley wrote:
> 
>> +	char devname[IFNAMSIZ];
>> +
>> +	ret = 0;
>> +	if (sk->sk_bound_dev_if == 0)
>> +		goto out;
>> +
>> +	ret = -EINVAL;
>> +	if (len < IFNAMSIZ)
>> +		goto out;
>> +	if (len > IFNAMSIZ)
>> +		len = IFNAMSIZ;
>> +
>> +	rcu_read_lock();
>> +	dev = dev_get_by_index_rcu(net, sk->sk_bound_dev_if);
>> +	if (dev)
>> +		strcpy(dev->name, devname);
>> +	rcu_read_unlock();
>> +	ret = -ENODEV;
> 
> You probably meant
> 
> 	strcpy(devname, dev->name)

Yes, that was a stupid mistake, I'll fix it.

> By the way, this is not really safe in case device is renamed

It's not much different from what's there:

	setsockopt("foo");

	rename foo -> bar

	index = getsockopt();
	if_indextoname(index) -> "bar"

I more raised the issue since you pass a 'char *' to setsockopt() but an 'int *'
to getsockopt(), I don't think any other value is non-symmetrical like this.

-Brian