linux-kernel - [PATCH 1/5] arm: factor out mmap ASLR into mmap

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Date:	Mon,  2 Mar 2015 16:19:44 -0800
From:	Kees Cook <keescook@...omium.org>
To:	akpm@...ux-foundation.org
Cc:	Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org,
	Russell King <linux@....linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux390@...ibm.com, x86@...nel.org,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Oleg Nesterov <oleg@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	"David A. Long" <dave.long@...aro.org>,
	Andrey Ryabinin <a.ryabinin@...sung.com>,
	Arun Chandran <achandran@...sta.com>,
	Yann Droneaud <ydroneaud@...eya.com>,
	Min-Hua Chen <orca.chen@...il.com>,
	Paul Burton <paul.burton@...tec.com>,
	Alex Smith <alex@...x-smith.me.uk>,
	Markos Chandras <markos.chandras@...tec.com>,
	Jeff Bailey <jeffbailey@...gle.com>,
	Vineeth Vijayan <vvijayan@...sta.com>,
	Michael Holzheu <holzheu@...ux.vnet.ibm.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	Hector Marco-Gisbert <hecmargi@....es>,
	Borislav Petkov <bp@...e.de>,
	Jan-Simon Möller <dl9pf@....de>,
	linux-arm-kernel@...ts.infradead.org, linux-mips@...ux-mips.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH 1/5] arm: factor out mmap ASLR into mmap_rnd

In preparation for exporting per-arch mmap randomization functions,
this moves the ASLR calculations for mmap on ARM into a separate routine.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/arm/mm/mmap.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
index 5e85ed371364..0f8bc158f2c6 100644
--- a/arch/arm/mm/mmap.c
+++ b/arch/arm/mm/mmap.c
@@ -169,14 +169,21 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 	return addr;
 }
 
-void arch_pick_mmap_layout(struct mm_struct *mm)
+static unsigned long mmap_rnd(void)
 {
-	unsigned long random_factor = 0UL;
+	unsigned long rnd = 0UL;
 
 	/* 8 bits of randomness in 20 address space bits */
 	if ((current->flags & PF_RANDOMIZE) &&
 	    !(current->personality & ADDR_NO_RANDOMIZE))
-		random_factor = (get_random_int() % (1 << 8)) << PAGE_SHIFT;
+		rnd = (get_random_int() % (1 << 8)) << PAGE_SHIFT;
+
+	return rnd;
+}
+
+void arch_pick_mmap_layout(struct mm_struct *mm)
+{
+	unsigned long random_factor = mmap_rnd();
 
 	if (mmap_is_legacy()) {
 		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
-- 
1.9.1

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