[2/3] net/unix: hook unix_socketpair() into LSM

Use the newly created LSM-hook for unix_socketpair(). The default hook
return-value is 0, so behavior stays the same unless LSMs start using
this hook.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
---
 net/unix/af_unix.c | 5 +++++
 1 file changed, 5 insertions(+)

On Mon, Apr 23, 2018 at 9:30 AM, David Herrmann <dh.herrmann@gmail.com> wrote:
> Use the newly created LSM-hook for unix_socketpair(). The default hook
> return-value is 0, so behavior stays the same unless LSMs start using
> this hook.
>
> Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
> ---
>  net/unix/af_unix.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index 68bb70a62afe..bc9705ace9b1 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -1371,6 +1371,11 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
>  static int unix_socketpair(struct socket *socka, struct socket *sockb)
>  {
>         struct sock *ska = socka->sk, *skb = sockb->sk;
> +       int err;
> +
> +       err = security_unix_stream_socketpair(ska, skb);
> +       if (err)
> +               return err;

I recognize that AF_UNIX is really the only protocol that supports
socketpair(2) at the moment, but I like to avoid protocol specific LSM
hooks whenever possible.  Unless someone can think of a good
objection, I would prefer to see the hook placed in __sys_socketpair()
instead (and obviously drop the "unix_stream" portion from the hook
name).

>         /* Join our sockets back to back */
>         sock_hold(ska);
> --
> 2.17.0

From: Paul Moore <paul@paul-moore.com>
Date: Tue, 24 Apr 2018 13:55:31 -0400

> On Mon, Apr 23, 2018 at 9:30 AM, David Herrmann <dh.herrmann@gmail.com> wrote:
>> Use the newly created LSM-hook for unix_socketpair(). The default hook
>> return-value is 0, so behavior stays the same unless LSMs start using
>> this hook.
>>
>> Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
>> ---
>>  net/unix/af_unix.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
>> index 68bb70a62afe..bc9705ace9b1 100644
>> --- a/net/unix/af_unix.c
>> +++ b/net/unix/af_unix.c
>> @@ -1371,6 +1371,11 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
>>  static int unix_socketpair(struct socket *socka, struct socket *sockb)
>>  {
>>         struct sock *ska = socka->sk, *skb = sockb->sk;
>> +       int err;
>> +
>> +       err = security_unix_stream_socketpair(ska, skb);
>> +       if (err)
>> +               return err;
> 
> I recognize that AF_UNIX is really the only protocol that supports
> socketpair(2) at the moment, but I like to avoid protocol specific LSM
> hooks whenever possible.  Unless someone can think of a good
> objection, I would prefer to see the hook placed in __sys_socketpair()
> instead (and obviously drop the "unix_stream" portion from the hook
> name).

The counterargument is that after 30 years no other protocol has grown
usage of this operation. :-)

On Tue, Apr 24, 2018 at 1:56 PM, David Miller <davem@davemloft.net> wrote:
> From: Paul Moore <paul@paul-moore.com>
> Date: Tue, 24 Apr 2018 13:55:31 -0400
>
>> On Mon, Apr 23, 2018 at 9:30 AM, David Herrmann <dh.herrmann@gmail.com> wrote:
>>> Use the newly created LSM-hook for unix_socketpair(). The default hook
>>> return-value is 0, so behavior stays the same unless LSMs start using
>>> this hook.
>>>
>>> Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
>>> ---
>>>  net/unix/af_unix.c | 5 +++++
>>>  1 file changed, 5 insertions(+)
>>>
>>> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
>>> index 68bb70a62afe..bc9705ace9b1 100644
>>> --- a/net/unix/af_unix.c
>>> +++ b/net/unix/af_unix.c
>>> @@ -1371,6 +1371,11 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
>>>  static int unix_socketpair(struct socket *socka, struct socket *sockb)
>>>  {
>>>         struct sock *ska = socka->sk, *skb = sockb->sk;
>>> +       int err;
>>> +
>>> +       err = security_unix_stream_socketpair(ska, skb);
>>> +       if (err)
>>> +               return err;
>>
>> I recognize that AF_UNIX is really the only protocol that supports
>> socketpair(2) at the moment, but I like to avoid protocol specific LSM
>> hooks whenever possible.  Unless someone can think of a good
>> objection, I would prefer to see the hook placed in __sys_socketpair()
>> instead (and obviously drop the "unix_stream" portion from the hook
>> name).
>
> The counterargument is that after 30 years no other protocol has grown
> usage of this operation. :-)

Call me a an optimist ;)