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From: Alex Vinokur on 5 May 2008 00:47
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/UNIXhelp/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

From: Michael Kerrisk on 6 May 2008 01:24
On Sun, 4 May 2008 21:47:21 -0700 (PDT), Alex Vinokur
<alexvn(a)users.sourceforge.net> 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/UNIXhelp/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.
From: Alex Vinokur on 6 May 2008 03:36
On May 6, 8:24 am, Michael Kerrisk <michael.kerr...(a)gmail.com> wrote:
> On Sun, 4 May 2008 21:47:21 -0700 (PDT), Alex Vinokur
>
> <ale...(a)users.sourceforge.net> 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



From: Michael Kerrisk on 7 May 2008 04:24
On Tue, 6 May 2008 00:36:27 -0700 (PDT), Alex Vinokur
<alexvn(a)users.sourceforge.net> wrote:

>On May 6, 8:24�am, Michael Kerrisk <michael.kerr...(a)gmail.com> wrote:
>> On Sun, 4 May 2008 21:47:21 -0700 (PDT), Alex Vinokur
>>
>> <ale...(a)users.sourceforge.net> 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/online/pages/man2/shmget.2.html

Cheers,

Michael
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