Re: syscall: sys_promote

[Qi Yong]

Ulrich Drepper wrote:

> On 8/29/05, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> wrote:
>  
>
> > Fixing it might be useful in some obscure cases anyway - POSIX threads
> > might benefit from it too, providing the functionality of changing all
> > thread uids at once isnt triggered for sensible threaded app behaviour.
> >    
>
> I would very much like to see that fixed.  Currently we have to change
> the UIDs/GIDs at userlevel with cross-thread calls implemented via
> signals.  This is user observable which is not correct.  This is
> probably the last area where we're not 100% POSIX compliant.
>
> As for adding this proposed syscall: it can only lead to chaos.  All
> kinds of user code correctly so assumes the IDs don't change over the
> lifetime of a process.  The solution for the problem has been
>  
After a user shell is promoted to root, its prompt is still $ instead of 
#. But why do we care?

> mentioned as well: re-exec.  This will require some code rewrite on
> the side of the applications but any decent daemon is hopefully soon
>  

OK, so any decent processes should not break into other processes' 
address space.
And let us use non-preemptive multitasking?

> support re-exec anyway for another reason: re-randomization of the
> address space.  What good does address space randomization do if the
> machines and programs are so damn stable that they keep running for
> months at a time?  nscd supports this now and I think openssh as well.
>  

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