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    SubjectRe: [RFC][PATCH] Deny CLONE_PARENT|CLONE_NEWPID|CLONE_SIGHAND combination
    Oleg Nesterov [oleg@redhat.com] wrote:
    | On 07/01, Sukadev Bhattiprolu wrote:
    | >
    | > Deny CLONE_PARENT|CLONE_NEWPID|CLONE_SIGHAND combination.
    | >
    | > CLONE_PARENT was used to implement an older threading model. For consistency
    | > with the CLONE_THREAD check in copy_pid_ns(), disable CLONE_PARENT and
    | > CLONE_SIGHAND with CLONE_NEWPID, at least until the required semantics of
    | > the pid namespaces are clear.
    | >
    | > Changelog[v2]:
    | > [Eric Biederman] Disable CLONE_SIGHAND also ???
    | >
    | > Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
    | > Acked-by: Roland McGrath <roland@redhat.com>
    | > ---
    | > kernel/pid_namespace.c | 2 +-
    | > 1 file changed, 1 insertion(+), 1 deletion(-)
    | >
    | > Index: linux-mmotm/kernel/pid_namespace.c
    | > ===================================================================
    | > --- linux-mmotm.orig/kernel/pid_namespace.c 2009-06-30 23:01:09.000000000 -0700
    | > +++ linux-mmotm/kernel/pid_namespace.c 2009-06-30 23:49:06.000000000 -0700
    | > @@ -118,7 +118,7 @@ struct pid_namespace *copy_pid_ns(unsign
    | > {
    | > if (!(flags & CLONE_NEWPID))
    | > return get_pid_ns(old_ns);
    | > - if (flags & CLONE_THREAD)
    | > + if (flags & (CLONE_THREAD|CLONE_PARENT|CLONE_SIGHAND))
    | > return ERR_PTR(-EINVAL);
    |
    | Still can't understand why CLONE_SIGHAND is forbidden...
    |
    | CLONE_SIGHAND doesn't mean we share the signal queue, so what is
    | the reason?

    I don't have a convincing reason. We could disable just the
    CLONE_NEWPID|CLONE_PARENT combination till we have a need for it. We
    talked about removing CLONE_PARENT but backed-off since some application
    may be using it. Disabling specific combinations like this (CLONE_NEWPID is
    relatively a new flag) could make it a little easier to remove CLONE_PARENT
    in the future.

    Sukadev


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