linux-kernel - [ 05/45] x86 get_unmapped_area(): use proper mmap base for bottom-up direction

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Date:	Sun, 18 Aug 2013 13:35:54 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Rik van Riel <riel@...hat.com>,
	Michel Lespinasse <walken@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Adrian Sendroiu <molecula2788@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [ 05/45] x86 get_unmapped_area(): use proper mmap base for bottom-up direction

3.10-stable review patch.  If anyone has any objections, please let me know.

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

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

commit df54d6fa54275ce59660453e29d1228c2b45a826 upstream.

When the stack is set to unlimited, the bottomup direction is used for
mmap-ings but the mmap_base is not used and thus effectively renders
ASLR for mmapings along with PIE useless.

Reviewed-by: Rik van Riel <riel@...hat.com>
Cc: Michel Lespinasse <walken@...gle.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Acked-by: Ingo Molnar <mingo@...nel.org>
Cc: Adrian Sendroiu <molecula2788@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kernel/sys_x86_64.c |    2 +-
 arch/x86/mm/mmap.c           |    2 +-
 include/linux/sched.h        |    1 +
 3 files changed, 3 insertions(+), 2 deletions(-)

--- a/arch/x86/kernel/sys_x86_64.c
+++ b/arch/x86/kernel/sys_x86_64.c
@@ -101,7 +101,7 @@ static void find_start_end(unsigned long
 				*begin = new_begin;
 		}
 	} else {
-		*begin = TASK_UNMAPPED_BASE;
+		*begin = mmap_legacy_base();
 		*end = TASK_SIZE;
 	}
 }
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -98,7 +98,7 @@ static unsigned long mmap_base(void)
  * Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64
  * does, but not when emulating X86_32
  */
-static unsigned long mmap_legacy_base(void)
+unsigned long mmap_legacy_base(void)
 {
 	if (mmap_is_ia32())
 		return TASK_UNMAPPED_BASE;
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -314,6 +314,7 @@ struct nsproxy;
 struct user_namespace;
 
 #ifdef CONFIG_MMU
+extern unsigned long mmap_legacy_base(void);
 extern void arch_pick_mmap_layout(struct mm_struct *mm);
 extern unsigned long
 arch_get_unmapped_area(struct file *, unsigned long, unsigned long,


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