linux-kernel - Re: [rfc 1/4] mm: Introduce may_adjust

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Date:	Thu, 24 Jul 2014 23:46:51 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Serge Hallyn <serge.hallyn@...ntu.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	keescook@...omium.org, tj@...nel.org, akpm@...ux-foundation.org,
	avagin@...nvz.org, ebiederm@...ssion.com, hpa@...or.com,
	serge.hallyn@...onical.com, xemul@...allels.com,
	segoon@...nwall.com, kamezawa.hiroyu@...fujitsu.com,
	mtk.manpages@...il.com, jln@...gle.com
Subject: Re: [rfc 1/4] mm: Introduce may_adjust_brk helper

On Thu, Jul 24, 2014 at 07:32:25PM +0000, Serge Hallyn wrote:
> Quoting Cyrill Gorcunov (gorcunov@...nvz.org):
> > To eliminate code duplication lets introduce may_adjust_brk
> > helper which we will use in brk() and prctl() syscalls.
> > 
> > Signed-off-by: Cyrill Gorcunov <gorcunov@...nvz.org>
> > Cc: Kees Cook <keescook@...omium.org>
> > Cc: Tejun Heo <tj@...nel.org>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Andrew Vagin <avagin@...nvz.org>
> > Cc: Eric W. Biederman <ebiederm@...ssion.com>
> > Cc: H. Peter Anvin <hpa@...or.com>
> > Cc: Serge Hallyn <serge.hallyn@...onical.com>
> > Cc: Pavel Emelyanov <xemul@...allels.com>
> > Cc: Vasiliy Kulikov <segoon@...nwall.com>
> > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > Cc: Michael Kerrisk <mtk.manpages@...il.com>
> > Cc: Julien Tinnes <jln@...gle.com>
> > ---
> >  include/linux/mm.h |   14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> > 
> > Index: linux-2.6.git/include/linux/mm.h
> > ===================================================================
> > --- linux-2.6.git.orig/include/linux/mm.h
> > +++ linux-2.6.git/include/linux/mm.h
> > @@ -18,6 +18,7 @@
> >  #include <linux/pfn.h>
> >  #include <linux/bit_spinlock.h>
> >  #include <linux/shrinker.h>
> > +#include <linux/resource.h>
> >  
> >  struct mempolicy;
> >  struct anon_vma;
> > @@ -1780,6 +1781,19 @@ extern struct vm_area_struct *copy_vma(s
> >  	bool *need_rmap_locks);
> >  extern void exit_mmap(struct mm_struct *);
> >  
> > +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) {
> 
> In the code you're replacing, this was RLIM_INFINITY.  Did you really
> mean for this to be RLIMIT_DATA, aka 2?

Good catch, thanks Serge! Better would be to pass the type of resource
(as Kees suggested) here instead of @rlim itself and sure to compare
with RLIM_INFINITY.
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