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    SubjectRe: [RFC][PATCH 0/3] fork: Add the ability to create tasks with given pids
    On 11/17, Pavel Emelyanov wrote:
    > Gentlemen, please, find some time for this, your ACK/NACK on the API proposal
    > is required badly.


    > The proposal is to introduce the CLONE_CHILD_USEPIDS flag for clone() syscall
    > and pass the pids values in the child_tidptr. In order not to introduce the
    > hole for the pid-reuse attack, using this flag will result in EPERM in case
    > the pid namespace we're trying to create pid in has at least one pid (except
    > for the init's one) generated with regular fork()/clone().
    > Currently Tejun and Oleg are worrying only about the intrusiveness of this
    > approach, although Oleg agrees, that it solves all the problems it should. The
    > previous attempts to implement the similar stuff stopped, but no objections
    > against this were expressed. So the decision of whether it's OK to go this
    > way or not is required.

    Yes, personally I'd prefer /proc/set_last_pid (or something similar) which
    simply writes to pid_ns->last_pid. Perhaps it is less convenient from the
    user-space pov (serialization, security) but it is much simpler.

    OTOH, I do not pretend I understand the user-space needs, so I won't argue.
    This series seems correct, the bugs we discussed are fixed.

    But. Speaking of API, it differs a bit compared to the previous version...

    > The API will be used like in the code below
    > /* restore new pid namespace with an init in it */
    > pid = clone(CLONE_NEWPID);

    Yes, CLONE_NEWPID | CLONE_CHILD_USEPIDS is not possible.

    Then how the array of pids in child_tidptr[] can be useful? If CLONE_NEWPID
    can't restore the pid_nr's in the parent namespaces, then probably this
    doesn't makes sense at all?

    IOW. I think we should either allow CLONE_NEWPID | CLONE_CHILD_USEPIDS
    (with additional check in set_pidmap() to ensure that CLONE_NEWPID
    comes with child_tidptr[0] == 1), or we should treat the "overloaded"
    child_tidptr as a simple pid_t.

    Again, I won't insist. Just I want to be sure we do not miss something
    adding the new API.


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      Last update: 2011-11-17 16:57    [W:0.031 / U:35.068 seconds]
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