[ 3.5.y.z extended stable ] Patch "x86 get_unmapped_area(): use proper mmap base for bottom-up" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    x86 get_unmapped_area(): use proper mmap base for bottom-up

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From dffad9e7f9adadaee3891ffee919ab656c90bcfa Mon Sep 17 00:00:00 2001
From: Radu Caragea <sinaelgl at gmail.com>
Date: Tue, 13 Aug 2013 16:00:59 -0700
Subject: [PATCH] x86 get_unmapped_area(): use proper mmap base for bottom-up
 direction

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.

Cc: Michel Lespinasse <walken at google.com>
Cc: Oleg Nesterov <oleg at redhat.com>
Reviewed-by: Rik van Riel <riel at redhat.com>
Acked-by: Ingo Molnar <mingo at kernel.org>
Cc: Adrian Sendroiu <molecula2788 at gmail.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 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(-)

diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
index b4d3c39..2145c1b 100644
--- 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 flags, unsigned long *begin,
 				*begin = new_begin;
 		}
 	} else {
-		*begin = TASK_UNMAPPED_BASE;
+		*begin = mmap_legacy_base();
 		*end = TASK_SIZE;
 	}
 }
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index 845df68..c1af323 100644
--- 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;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index ebd15f9..2248790 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -388,6 +388,7 @@ extern int sysctl_max_map_count;
 #include <linux/aio.h>

 #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,
--
1.8.3.2