Hi Chris,

Andrew Morton wrote:

Ingo Oeser [off-list ref] wrote:

quoted

 -int scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)
 -{
 -	struct task_struct *p = current;
 -	scm->creds = (struct ucred) {
 -		.uid = p->uid,
 -		.gid = p->gid,
 -		.pid = p->tgid
 -	};
 -	scm->fp = NULL;
 -	scm->sid = security_sk_sid(sock->sk, NULL, 0);
 -	scm->seq = 0;
 -	if (msg->msg_controllen <= 0)
 -		return 0;
 -	return __scm_send(sock, msg, scm);
 -}

It's worth noting that scm_send() will call security_sk_sid() even if
(msg->msg_controllen <= 0).

Chris, do you know if this is needed in this case?

If that test is likely to be true with any frequency then perhaps we can
optimise things...

That test seems to be the original intention for the splitup. 

The security modules just put their hooks here. Maybe we can
fold these hooks into __scm_send() and have the old
splitup again to get the old code paths back.

It seems that the credential copy in af_unix.c 

memcpy(UNIXCREDS(skb), &siocb->scm->creds, sizeof(struct ucred));
if (siocb->scm->fp)
            unix_attach_fds(siocb->scm, skb);

doesn't depend on the "msg_controllen <= 0" test. If we can introduce this 
dependency there, we can put credential setup into __scm_send().

I would suggest we fold these two lines into a function and decide this later.

Chris, would this suffice?

Regards

Ingo Oeser

BTW: ioe-lkml@rameria.de is simply netdev@axxeo.de at work :-)