[3.19.y-ckt stable] Patch "mips: extract logic for mmap_rnd()" has been added to the 3.19.y-ckt tree

[Kamal Mostafa]

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

    mips: extract logic for mmap_rnd()

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    https://git.launchpad.net/~canonical-kernel/linux/+git/linux-stable-ckt/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt21.

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

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 33dceeccf2769742bbacfcd8e324aece83a61dc9 Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook at chromium.org>
Date: Tue, 14 Apr 2015 15:47:51 -0700
Subject: mips: extract logic for mmap_rnd()

commit 1f0569df0b0285e7ec2432d804a4921b06a61618 upstream.

In preparation for splitting out ET_DYN ASLR, extract the mmap ASLR
selection into a separate function.

Signed-off-by: Kees Cook <keescook at chromium.org>
Reviewed-by: Ingo Molnar <mingo at kernel.org>
Cc: Ralf Baechle <ralf at linux-mips.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/mips/mm/mmap.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
index f1baadd..9a4f1f5 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -142,18 +142,26 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp,
 			addr0, len, pgoff, flags, DOWN);
 }

+static unsigned long mmap_rnd(void)
+{
+	unsigned long rnd;
+
+	rnd = (unsigned long)get_random_int();
+	rnd <<= PAGE_SHIFT;
+	if (TASK_IS_32BIT_ADDR)
+		rnd &= 0xfffffful;
+	else
+		rnd &= 0xffffffful;
+
+	return rnd;
+}
+
 void arch_pick_mmap_layout(struct mm_struct *mm)
 {
 	unsigned long random_factor = 0UL;

-	if (current->flags & PF_RANDOMIZE) {
-		random_factor = get_random_int();
-		random_factor = random_factor << PAGE_SHIFT;
-		if (TASK_IS_32BIT_ADDR)
-			random_factor &= 0xfffffful;
-		else
-			random_factor &= 0xffffffful;
-	}
+	if (current->flags & PF_RANDOMIZE)
+		random_factor = mmap_rnd();

 	if (mmap_is_legacy()) {
 		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
--
2.7.4