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

From: Pavel Emelyanov <xemul@parallels.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Brian Haley <brian.haley@hp.com>,
	Linux Netdev List <netdev@vger.kernel.org>,
	David Miller <davem@davemloft.net>
Subject: Re: [PATCH net-next] sockopt: Make SO_BINDTODEVICE readable
Date: Tue, 23 Oct 2012 01:10:22 +0400	[thread overview]
Message-ID: <5085B63E.5070504@parallels.com> (raw)
In-Reply-To: <1350938702.8609.1299.camel@edumazet-glaptop>

On 10/23/2012 12:45 AM, 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)
> 
> By the way, this is not really safe in case device is renamed

Good point, actually. Getting a device name may be not very safe in terms of --
once we have the name there's no 100% guarantee, that this name corresponds to the
actual device the socket is bound to (it could be renamed after we strcpy-ed its
name). This problem doesn't exist when we get device index, as it cannot be changed.

Thanks,
Pavel