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    SubjectRe: [PATCH] scm: fold __scm_send() into scm_send()
    * Chris Wright (chrisw@sous-sol.org) wrote:
    > * Ingo Oeser (netdev@axxeo.de) wrote:
    > > Hi Chris,
    > >
    > > Andrew Morton wrote:
    > > > Ingo Oeser <ioe-lkml@rameria.de> 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. 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.

    thanks,
    -chris
    -
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