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    SubjectRe: [PATCH 2.5.30+] Fourth attempt at a shared credentials patch
    In article <>,
    Dave McCracken <> wrote:
    >--On Thursday, August 08, 2002 11:55:05 PM +0200 Trond Myklebust
    ><> wrote:
    >> What if one thread is doing an RPC call while the other is changing
    >> the 'groups' entry?
    >Gah. Good point. Ok, I've added locking to the cred structure to handle

    Please don't do this with locking, I really think the right thing to do
    is to have a "duplicate()" function, and when you pass credentials off
    to something, you dup them at that point.

    If you start off as non-root, and then execve suid into root, a pending
    NFS request should _not_ suddently have the credentials changed under
    it. Yet clearly that kind of thing can't just be locked either.

    Along with copy-on-write semantics, this should perform perfectly well
    (ie "duplicate()" would only increment a count, and then setuid() would
    have to have code soemthing like

    if (cred->count > 1) {
    newcred = alloc_cred();
    copy_cred(newcred, cred);
    for_each_cred_group(p) {
    p->cred = newcred;


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