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

[Serge Hallyn <serge.hallyn@ubuntu.com>]

Quoting Cyrill Gorcunov (gorcunov@openvz.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@openvz.org>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Andrew Vagin <avagin@openvz.org>
> Cc: Eric W. Biederman <ebiederm@xmission.com>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Serge Hallyn <serge.hallyn@canonical.com>
> Cc: Pavel Emelyanov <xemul@parallels.com>
> Cc: Vasiliy Kulikov <segoon@openwall.com>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Cc: Michael Kerrisk <mtk.manpages@gmail.com>
> Cc: Julien Tinnes <jln@google.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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