Chris Wright <[EMAIL PROTECTED]> wrote:
>
> * Chris Wright ([EMAIL PROTECTED]) wrote:
> > * Ingo Oeser ([EMAIL PROTECTED]) wrote:
> > > Hi Chris,
> > >
> > > Andrew Morton wrote:
> > > > Ingo Oeser <[EMAIL PROTECTED]> wrote:
> > > > >
> > > > > -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?
> >
> > This whole thing is looking broken. I'm still trying to find the original
> > patch which caused the series of broken patches on top.
>
> OK, it starts here from Catherine's patch:
>
> include/net/scm.h::scm_recv()
> + if (test_bit(SOCK_PASSSEC, &sock->flags)) {
> + err = security_sid_to_context(scm->sid, &scontext,
> &scontext_len);
> + if (!err)
> + put_cmsg(msg, SOL_SOCKET, SCM_SECURITY, scontext_len,
> scontext);
> + }
>
> Catherine, the security_sid_to_context() is a raw SELinux function which
> crept into core code and should not have been there. The fallout fixes
> included conditionally exporting security_sid_to_context, and finally
> scm_send/recv unlining.
Yes. So we're OK up the uninlining, right?
> The end result in -mm looks broken to me.
> Specifically, it now does:
>
> ucred->uid = tsk->uid;
> ucred->gid = tsk->gid;
> ucred->pid = tsk->tgid;
> scm->fp = NULL;
> scm->seq = 0;
> if (msg->msg_controllen <= 0)
> return 0;
>
> scm->sid = security_sk_sid(sock->sk, NULL, 0);
>
> The point of Catherine's original patch was to make sure there's always
> a security identifier associated with AF_UNIX messages. So receiver
> can always check it (same as having credentials even w/out sender
> control message passing them). Now we will have garbage for sid.
This answers the question I've been asking all and sundry for a week, thanks ;)
So:
- scm-fold-__scm_send-into-scm_send.patch is OK
- scm_send-speedup.patch is wrong
- Catherine's patch introduces a possibly-significant performance
problem: we're now calling the expensive-on-SELinux security_sk_sid()
more frequently than we used to.
- That "initialise scm->creds via a temporary struct" trick still
generates bad code.
I actually have enough to be going on with here - I'll drop it all.
-
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