linux-kernel - [110/121] x86 get_unmapped_area: Access mmap_legacy_base through mm

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Date:	Sun, 08 Sep 2013 03:52:01 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Michel Lespinasse" <walken@...gle.com>,
	"Ingo Molnar" <mingo@...e.hu>, "Rik van Riel" <riel@...hat.com>,
	"Adrian Sendroiu" <molecula2788@...il.com>,
	"Kamal Mostafa" <kamal@...onical.com>, "Greg KH" <greg@...ah.com>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Radu Caragea" <sinaelgl@...il.com>,
	"Oleg Nesterov" <oleg@...hat.com>
Subject: [110/121] x86 get_unmapped_area: Access mmap_legacy_base through
 mm_struct member

3.2.51-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Radu Caragea <sinaelgl@...il.com>

commit 41aacc1eea645c99edbe8fbcf78a97dc9b862adc upstream.

This is the updated version of df54d6fa5427 ("x86 get_unmapped_area():
use proper mmap base for bottom-up direction") that only randomizes the
mmap base address once.

Signed-off-by: Radu Caragea <sinaelgl@...il.com>
Reported-and-tested-by: Jeff Shorey <shoreyjeff@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Michel Lespinasse <walken@...gle.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Rik van Riel <riel@...hat.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Adrian Sendroiu <molecula2788@...il.com>
Cc: Greg KH <greg@...ah.com>
Cc: Kamal Mostafa <kamal@...onical.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/kernel/sys_x86_64.c | 2 +-
 arch/x86/mm/mmap.c           | 6 ++++--
 include/linux/mm_types.h     | 1 +
 3 files changed, 6 insertions(+), 3 deletions(-)

--- a/arch/x86/kernel/sys_x86_64.c
+++ b/arch/x86/kernel/sys_x86_64.c
@@ -115,7 +115,7 @@ static void find_start_end(unsigned long
 				*begin = new_begin;
 		}
 	} else {
-		*begin = TASK_UNMAPPED_BASE;
+		*begin = current->mm->mmap_legacy_base;
 		*end = TASK_SIZE;
 	}
 }
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -112,12 +112,14 @@ static unsigned long mmap_legacy_base(vo
  */
 void arch_pick_mmap_layout(struct mm_struct *mm)
 {
+	mm->mmap_legacy_base = mmap_legacy_base();
+	mm->mmap_base = mmap_base();
+
 	if (mmap_is_legacy()) {
-		mm->mmap_base = mmap_legacy_base();
+		mm->mmap_base = mm->mmap_legacy_base;
 		mm->get_unmapped_area = arch_get_unmapped_area;
 		mm->unmap_area = arch_unmap_area;
 	} else {
-		mm->mmap_base = mmap_base();
 		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 		mm->unmap_area = arch_unmap_area_topdown;
 	}
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -297,6 +297,7 @@ struct mm_struct {
 	void (*unmap_area) (struct mm_struct *mm, unsigned long addr);
 #endif
 	unsigned long mmap_base;		/* base of mmap area */
+	unsigned long mmap_legacy_base;         /* base of mmap area in bottom-up allocations */
 	unsigned long task_size;		/* size of task vm space */
 	unsigned long cached_hole_size; 	/* if non-zero, the largest hole below free_area_cache */
 	unsigned long free_area_cache;		/* first hole of size cached_hole_size or larger */

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