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    SubjectRe: [RFC][PATCH 3/5] Determine if sender is from ancestor ns
    On Mon, Dec 01, 2008 at 12:15:06PM -0800, Sukadev Bhattiprolu wrote:
    > Bastian Blank [] wrote:
    > | If I see this correctly this information is already covered in si_code
    > | with SI_USER and SI_TKILL. SI_KERNEL is used for explicit kernel
    > | generated signals.
    > Yes, but si_code from sys_rt_sigqueueinfo() cannot be trusted.

    sys_rt_sigqueueinfo disallows setting si_code to any value which
    describes kernel signals from userspace. So using SI_FROMUSER should be

    > IOW, we need to find the namespace of the sender only if the sender is
    > a user process. If signal is originating from kernel, safely checking
    > namespace becomes more complex.

    Where does this imply checking sender for kernel generated signals?

    > Yes, current approach is somewhat hacky. We tried other approaches
    > before and they were either intrusive or required non-trivial changes
    > to semantics of signals to global init or both.


    > | > +static inline int siginfo_from_ancestor_ns(struct task_struct *t,
    > | > + siginfo_t *info)
    > | > +{
    > | > + if (!is_si_special(info) && (info->si_signo & SIG_FROM_USER)) {
    > | > + /* if t can't see us we are from parent ns */
    > | What?
    > I assume your question is about the comment :-)


    > Yes, a process can see all its descendants and processes in descendant
    > namespaces. But it can only see its ancestors upto the most recent
    > CLONE_NEWPID. (kind of like chroot in filesystems). So if receiver
    > can't see sender, sender must be an ancestor.

    Please add a complete comment to the function which describes the
    function. And don't us "it" for not defined entities.


    I have never understood the female capacity to avoid a direct answer to
    any question.
    -- Spock, "This Side of Paradise", stardate 3417.3

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