Difference between an owner and a creator of IPC facility entry - Unix

This is a discussion on Difference between an owner and a creator of IPC facility entry - Unix ; What is the difference between an owner and a creator of IPC facility entry (for instance, segment of shared memory) ---------------------- man ipcs(1) http://www.iti.cs.tu-bs.de/cgi-bin/U...man-cgi?ipcs+1 OWNER - The login name of the owner of the facility entry. CREATOR - The login ...

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Thread: Difference between an owner and a creator of IPC facility entry

  1. Difference between an owner and a creator of IPC facility entry

    What is the difference between an owner and a creator of IPC facility
    entry (for instance, segment of shared memory)

    ----------------------
    man ipcs(1)
    http://www.iti.cs.tu-bs.de/cgi-bin/U...man-cgi?ipcs+1

    OWNER - The login name of the owner of the facility entry.
    CREATOR - The login name of the creator of the facility entry.
    ----------------------

    It is clear what is a creator; but what an owner is?

    Alex Vinokur
    email: alex DOT vinokur AT gmail DOT com
    http://mathforum.org/library/view/10978.html
    http://sourceforge.net/users/alexvn


  2. Re: Difference between an owner and a creator of IPC facility entry

    On Sun, 4 May 2008 21:47:21 -0700 (PDT), Alex Vinokur
    wrote:

    >What is the difference between an owner and a creator of IPC facility
    >entry (for instance, segment of shared memory)
    >
    >----------------------
    >man ipcs(1)
    >http://www.iti.cs.tu-bs.de/cgi-bin/U...man-cgi?ipcs+1
    >
    >OWNER - The login name of the owner of the facility entry.
    >CREATOR - The login name of the creator of the facility entry.
    >----------------------
    >
    >It is clear what is a creator; but what an owner is?


    The creator is (as you see) obviously the (effective) UID and GID of
    the process that created the object. These attributes cannot be
    changed.

    The owner is another nominated UID plus GID -- these can be
    set/modified via IPC_SET.

    When accessing an object owner (group) permissions are granted to a
    process if its effective user (group) ID matches either the creator or
    the owner UID (GID). Also, certain IPC operations (e.g., IPC_SET,
    IPC_RMID) can be done by the creator or the owner UID. Having a
    mutable owner makes it possible to allow a UID/GID other than the
    creating process to have "owner" rights on the object.

  3. Re: Difference between an owner and a creator of IPC facility entry

    On May 6, 8:24*am, Michael Kerrisk wrote:
    > On Sun, 4 May 2008 21:47:21 -0700 (PDT), Alex Vinokur
    >
    > wrote:
    > >What is the difference between an owner and a creator of IPC facility
    > >entry (for instance, segment of shared memory)

    [snipped]
    >
    > The owner is another nominated UID plus GID *-- these can be
    > set/modified via IPC_SET.
    >

    [snipped]

    Thanks.

    So, if shmctl (..., IPC_SET) is not used, then CUID == UID.
    Is it true?

    Alex Vinokur
    email: alex DOT vinokur AT gmail DOT com
    http://mathforum.org/library/view/10978.html
    http://sourceforge.net/users/alexvn




  4. Re: Difference between an owner and a creator of IPC facility entry

    On Tue, 6 May 2008 00:36:27 -0700 (PDT), Alex Vinokur
    wrote:

    >On May 6, 8:24*am, Michael Kerrisk wrote:
    >> On Sun, 4 May 2008 21:47:21 -0700 (PDT), Alex Vinokur
    >>
    >> wrote:
    >> >What is the difference between an owner and a creator of IPC facility
    >> >entry (for instance, segment of shared memory)

    >[snipped]
    >>
    >> The owner is another nominated UID plus GID *-- these can be
    >> set/modified via IPC_SET.
    >>

    >[snipped]
    >
    >Thanks.
    >
    >So, if shmctl (..., IPC_SET) is not used, then CUID == UID.
    >Is it true?


    Yes.

    See
    http://www.kernel.org/doc/man-pages/.../shmget.2.html

    Cheers,

    Michael

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