[rfc 1/4] mm: Introduce may_adjust_brk helper

[Cyrill Gorcunov <gorcunov@openvz.org>]

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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) {
+		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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