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    SubjectRe: [PATCH] user namespace: make signal.c respect user namespaces
    On 09/27, Serge Hallyn wrote:
    >
    > Quoting Oleg Nesterov (oleg@redhat.com):
    > > On 09/25, Serge E. Hallyn wrote:
    > > >
    > > > Yes, that's the case I was talking about. That then proceeds through
    > > > send_signal().
    > >
    > > It doesn't?
    >
    > No, I was saying it *does*.

    But it doesn't ;)

    Serge, there is some misunderstanding. And I do not know who is confused,
    me or your.

    ptrace_signal() simply fills *info with some "random" data before
    processing the signal. It doesn't pass this info to send_signal().

    If the debuggure wants something meaningfull in *info, it should
    fill it itself via PTRACE_SETSIGINFO. This handles the case when
    the debugger doesn't really care and only changes signr.

    > > +static inline fixup_uid(struct siginfo *info, struct task_struct *t)
    > > +{
    > > +#ifdef CONFIG_USER_NS
    > > + if (current_user_ns() == task_cred_xxx(t, user_ns)))
    > > +#endif
    > > + return;
    > > +
    > > + if (SI_FROMKERNEL(info))
    > > + switch (info->si_code & __SI_MASK) {
    > > + default:
    > > + return;
    > > +
    > > + case __SI_CHLD:
    > > + case __SI_MESGQ:
    > > + break;
    > > + }
    > > +
    > > + info->si_uid = user_ns_map_uid(task_cred_xxx(t, user_ns),
    > > + current_cred(), info->si_uid);
    > > +}
    > > +
    > > static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
    > > int group, int from_ancestor_ns)
    > > {
    > > @@ -1088,6 +1109,9 @@ static int __send_signal(int sig, struct
    > > q->info.si_pid = 0;
    > > break;
    > > }
    > > +
    > > + fixup_uid(info, t);
    > > +
    > > } else if (!is_si_special(info)) {
    > > if (sig >= SIGRTMIN && info->si_code != SI_USER) {
    > > /*
    >
    > It certainly is much simpler. I'll take some time to walk through all
    > of send_signal again and make sure I understand what it does in all
    > the cases.

    Thanks.



    As for ptrace_signal(), it can use the same helper too. Once again,
    debugger can use PTRACE_SETSIGINFO, if we really want to fixup si_uid
    we should do this even if signr == info->si_signo. OTOH, we do not
    know what debugger puts in this chunk of memory. This is like
    sigqueueinfo().

    Or we can simply leave this code as is. I do not think this si_uid
    (in this case) is really important.

    Oleg.



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