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    SubjectRe: [RFC][PATCH 7/7][v4] SI_TKILL: Masquerade si_pid when crossing pid ns boundary
    On 12/24, Sukadev Bhattiprolu wrote:
    >
    > --- a/kernel/signal.c
    > +++ b/kernel/signal.c
    > @@ -2385,17 +2385,22 @@ static int do_tkill(pid_t tgid, pid_t pid, int sig)
    > struct siginfo info;
    > struct task_struct *p;
    > unsigned long flags;
    > + struct pid_namespace *ns;
    >
    > error = -ESRCH;
    > info.si_signo = sig;
    > info.si_errno = 0;
    > info.si_code = SI_TKILL;
    > - info.si_pid = task_tgid_vnr(current);
    > info.si_uid = current_uid();
    >
    > rcu_read_lock();
    > p = find_task_by_vpid(pid);
    > if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) {
    > + ns = task_active_pid_ns(p);
    > + if (ns)
    > + info.si_pid = task_tgid_nr_ns(current, ns);
    > + else
    > + info.si_pid = task_tgid_vnr(current);

    if ns == 0, "p" won't see the signal anyway, so all we need is

    - info.si_pid = task_tgid_vnr(current);
    + info.si_pid = task_tgid_nr_ns(current, task_active_ns(p));

    like we do in __do_notify().


    But. this of course doesn't work for sys_kill(). Can't we change the helpers
    which send SI_FROMUSER() signals so that they do not fill .si_pid at all?
    Then send_signal() can do:

    default:
    copy_siginfo(&q->info, info);
    info.si_pid = 0;
    if (!from_ancestot_ns)
    info.si_pid = task_tgid_nr_ns(current, ...);

    ?

    Yes, we use "current". But we already used it in siginfo_from_ancestor_ns().

    Oleg.



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