linux-kernel - Re: [PATCH net-next 2/2] tun: enable socket system calls

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Message-ID: <549DB410.8000002@fb.com>
Date:	Fri, 26 Dec 2014 14:16:32 -0500
From:	Alex Gartrell <agartrell@...com>
To:	Jason Wang <jasowang@...hat.com>, <davem@...emloft.net>,
	<herbert@...dor.apana.org.au>
CC:	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<kernel-team@...com>
Subject: Re: [PATCH net-next 2/2] tun: enable socket system calls

Hello Jason,

Thanks for commenting.

On 12/26/14 4:43 AM, Jason Wang wrote:
>
> On 12/26/2014 02:50 PM, Alex Gartrell wrote:
>> By setting private_data to a socket and private_data_is_socket to true, we
>> can use the socket syscalls.  We also can't just blindly use private_data
>> anymore, so there's a __tun_file_get function that returns the container_of
>> private_data appropriately.
>
> So this in fact expose other socket syscalls to userspace. But some of
> proto_ops was not supported. E.g consider what happens if a bind() was
> called for tun socket?

Yeah, I erroneously assumed that NULL => sock_no_*, but a quick glance 
assures me that that's not the case.  In this case, I'd need to 
introduce another patch that sets all of the additional ops to sock_no_*.

>> +static struct tun_file *tun_file_from_file(struct file *file)
>> +{
>> +	struct socket *s = (struct socket *)file->private_data;
>> +
>> +	if (!s)
>
> Can s be NULL here? If yes, why tun_get() didn't check for NULL?

This check is just to ensure that tun_get_socket continues to work in 
the right way when passed a file with private_data set to NULL.

Thanks,
-- 
Alex Gartrell <agartrell@...com>
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