Re: [rfc 1/4] mm: Introduce may_adjust_brk helper

[Cyrill Gorcunov]

On Thu, Jul 24, 2014 at 12:18:56PM -0700, Kees Cook wrote:
> >
> > +static inline int may_adjust_brk(unsigned long rlim,
> > +                                unsigned long new_brk,
> > +                                unsigned long start_brk,
> > +                                unsigned long end_data,
> > +                                unsigned long start_data)
> > +{
> > +       if (rlim < RLIMIT_DATA) {
> 
> Won't rlim always be the value from a call to rlimit(RLIMIT_DATA)? Is
> there a good reason to not just put the rlimit() call in
> may_adjust_brk()? This would actually be an optimization in the
> prctl_set_mm case, since now it calls rlimit() unconditionally, but
> doesn't need to.

Nope, we use it for rlimit(RLIMIT_STACK) when checking for
@start_stack member.
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