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    Subject[PATCH 2/4] signals: send_signal: use si_fromuser() to detect from_ancestor_ns
    Change send_signal() to use si_fromuser(). From now SEND_SIG_NOINFO
    triggers the "from_ancestor_ns" check.

    This fixes reparent_thread()->group_send_sig_info(pdeath_signal)
    behaviour, before this patch send_signal() does not detect the
    cross-namespace case when the child of the dying parent belongs
    to the sub-namespace.

    This patch can affect the behaviour of send_sig(), kill_pgrp() and
    kill_pid() when the caller sends the signal to the sub-namespace
    with "priv == 0" but surprisingly all callers seem to use them
    correctly, including disassociate_ctty(on_exit).

    Except: drivers/staging/comedi/drivers/addi-data/*.c incorrectly
    use send_sig(priv => 0). But his is minor and should be fixed
    anyway.
    Reported-by: Daniel Lezcano <dlezcano@fr.ibm.com>
    Signed-off-by: Oleg Nesterov <oleg@redhat.com>
    ---
    kernel/signal.c | 5 ++---
    1 file changed, 2 insertions(+), 3 deletions(-)
    --- TTT_32/kernel/signal.c~FU_2_SEND_SIGNAL 2009-10-04 02:21:55.000000000 +0200
    +++ TTT_32/kernel/signal.c 2009-10-04 03:09:44.000000000 +0200
    @@ -928,9 +928,8 @@ static int send_signal(int sig, struct s
    int from_ancestor_ns = 0;

    #ifdef CONFIG_PID_NS
    - if (!is_si_special(info) && SI_FROMUSER(info) &&
    - task_pid_nr_ns(current, task_active_pid_ns(t)) <= 0)
    - from_ancestor_ns = 1;
    + from_ancestor_ns = si_fromuser(info) &&
    + !task_pid_nr_ns(current, task_active_pid_ns(t));
    #endif

    return __send_signal(sig, info, t, group, from_ancestor_ns);


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