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

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Message-ID: <20140724193225.GT26600@ubuntumail>
Date:	Thu, 24 Jul 2014 19:32:25 +0000
From:	Serge Hallyn <serge.hallyn@...ntu.com>
To:	Cyrill Gorcunov <gorcunov@...nvz.org>
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

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?

> +		if (((new_brk - start_brk) + (end_data - start_data)) > rlim)
> +			return -ENOSPC;
> +	}
> +	return 0;
> +}
> +
>  extern int mm_take_all_locks(struct mm_struct *mm);
>  extern void mm_drop_all_locks(struct mm_struct *mm);
>  
> 
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