Re: message queue limits

[Marcelo Tosatti <marcelo.tosatti@cyclades.com>]

On Thu, Apr 15, 2004 at 12:24:11PM -0700, Andrew Morton wrote:
> Marcelo Tosatti <marcelo.tosatti@cyclades.com> wrote:
> >
> > On Sun, Apr 11, 2004 at 10:48:28PM -0700, Ulrich Drepper wrote:
> >  > Something has to change in the way message queues are created.
> >  > Currently it is possible for an unprivileged user to exhaust all mq
> >  > slots so that only root can create a few more.  Any other unprivileged
> >  > user has no change to create anything.
> >  > 
> >  > I think it is necessary to create a per-user limit instead of a
> >  > system-wide limit.
> > 
> >  Actually, there is no infrastructure to account for per-UID limits right now AFAICS 
> >  (please someone correct me) at ALL. We need to account and limit for per-user
> > 
> >  - pending signals
> >  - message queues
> 
> The stuff in kernel/user.c may be sufficient for this.

Oh, sweat! I'll try adding a "atomic_t signal_pending" to "user_struct" 
to be checked at send_signal(), and then go for message queue limiting.

Something which sucks is to add a atomic read/inc at each send signal operation.

Can we avoid the locking in some way?