Messages in this thread |  | | Date | Sun, 8 Sep 2002 17:00:04 -0500 | From | Amos Waterland <> | Subject | Re: [PATCH] POSIX message queues |
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On Sat, Sep 07, 2002 at 05:17:35PM +0200, Ingo Molnar wrote: > > On Sat, 7 Sep 2002 pwaechtler@mac.com wrote: > > > OTOH I can't see a _big_ problem when a process with sufficient > > permissions can trash the message queues - otherwise I wonder why file > > permissions are granted "per user" and not "per process". > > yes - furthermore, processes from the same user can 'trash' queues anyway, > via ptrace() or mmaping /proc.
That is correct, but it is not the issue though. The issue is that completely unrelated processes can spoof/destroy each other's messages.
If a queue is set up with mq_open(name, O_CREAT|O_RDWR, S_IWOTH, &attr), the process which set it up expects that "others" (processes not owned by the user or by users in his/her group) will be able to send, and only send, messages. If shared memory is used, "others" must be able to update the data structures representing the queue, so they will be able to do a lot more than just send.
The fundamental problem is that filesystem permissions do not map cleanly to message queue permissions. Does this make sense? Thanks.
Amos Waterland - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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