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SubjectRe: About ACL for IPC Object
I have tested posix sem,posix shm and posix msg queue for ACL on
fedora 12 with kernel 2.6.32.

Posix sem and posix shm using tmpfs monted by default support ACL well .
Posix msg queue use mqueue fs mounted by manual but it seem not
surpoort ACL well. It failed for setting named ACL item:
$ mkdir /dev/mqueue
$ mount -o rw, acl -t mqueue none /dev/mqueue
$cd /dev/mqueue
"/mq" msg queue object created and used by processes properly

$getfacl mq
#file: mq

$setfacl -m u:testuser:rw mq /* failed here*/
$setfacl: mq :Operation not supported
but mqueue fs works well for setting owner user and owner group items.

I am not sure whether mqueue don't support acl or I make mistake.

2010/1/22 Américo Wang <>:
> (Top-posting fixed.)
> On Fri, Jan 22, 2010 at 5:15 PM, zhou peng <> wrote:
>> 2010/1/21 Christoph Hellwig <>:
>>> On Wed, Jan 20, 2010 at 07:02:27PM -0800, Casey Schaufler wrote:
>>>> zhou peng wrote:
>>>> > Hi all,
>>>> >
>>>> > There are ACL in file system, but why there are no ACL implementation
>>>> > in IPC object, eg. shm, message queue, FIFO?
>>>> >
>>>> Most people haven't noticed that IPC objects are even there, much less
>>>> that they have mode bits and not ACLs. Even when we were doing security
>>>> evaluations on Unix boxes in the 1990's they were considered insufficiently
>>>> interesting to justify the additional work to do ACLs.
>>>> If you really want ACLs on IPC objects it would make a dandy little
>>>> project for a summer. I would be happy to review patches.
>> Thanks. It's interesting to add ACL over IPC objects. I want to have a try.
>>> Or use the posix IPC mechanisms.  The Posix shared memory has ACL by
>>> using tmpfs as the backing store, and we could add similar support to
>>> Posix messages queues as they are also backed by a normal filesystem.
>> Christoph Hellwig, This way may be convinent. Could you give some
>> detailed message. :)
>> I only find /proc/ipc/shm file which contain the info of shm objs,and
>> tmpfs on /dev/shm which is empty.
>>> Adding this support to the old SYSV IPC mechanisms would be much harder
>>> as they do not fit into the file backed model we use everywhere else at
>>> all.
>> Just like file objects, the mode bits are implment over IPC objects
>> without file backed, so I think adding ACL support to IPC objects may
>> be somewhat reasonable :)
>> Thank you all for so many solutions.
>> I want to control some IPC object (shm, msg queue, semphore) can be
>> accessed by which named user or named group just like file objects ACL
>> do.
>> I studied the solution you all referred, The SELinux is powerful but
>> may be somewhat complicated. And I am confused with Christoph
>> Hellwig‘s solution using tmpfs.
> Well, only posix semphores and posix share memory use tmpfs, I think,
> posix msg queues use "mqueue" instead.

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