Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753583AbdFSShS (ORCPT + 2 others); Mon, 19 Jun 2017 14:37:18 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:52454 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752908AbdFSShP (ORCPT ); Mon, 19 Jun 2017 14:37:15 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Kees Cook , Oleg Nesterov , Andy Lutomirski , Andrew Morton , Linus Torvalds , Ben Hutchings , Willy Tarreau Subject: [PATCH 3.10 266/268] x86: standardize mmap_rnd() usage Date: Mon, 19 Jun 2017 20:32:45 +0200 Message-Id: <1497897167-14556-267-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1497897167-14556-1-git-send-email-w@1wt.eu> References: <1497897167-14556-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: From: Kees Cook commit 82168140bc4cec7ec9bad39705518541149ff8b7 upstream. In preparation for splitting out ET_DYN ASLR, this refactors the use of mmap_rnd() to be used similarly to arm, and extracts the checking of PF_RANDOMIZE. Signed-off-by: Kees Cook Reviewed-by: Ingo Molnar Cc: Oleg Nesterov Cc: Andy Lutomirski Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings Signed-off-by: Willy Tarreau --- arch/x86/mm/mmap.c | 36 ++++++++++++++++++++---------------- 1 file changed, 20 insertions(+), 16 deletions(-) diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 75f9e5d..0e42676 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -67,22 +67,21 @@ static int mmap_is_legacy(void) static unsigned long mmap_rnd(void) { - unsigned long rnd = 0; + unsigned long rnd; /* - * 8 bits of randomness in 32bit mmaps, 20 address space bits - * 28 bits of randomness in 64bit mmaps, 40 address space bits - */ - if (current->flags & PF_RANDOMIZE) { - if (mmap_is_ia32()) - rnd = get_random_int() % (1<<8); - else - rnd = get_random_int() % (1<<28); - } + * 8 bits of randomness in 32bit mmaps, 20 address space bits + * 28 bits of randomness in 64bit mmaps, 40 address space bits + */ + if (mmap_is_ia32()) + rnd = (unsigned long)get_random_int() % (1<<8); + else + rnd = (unsigned long)get_random_int() % (1<<28); + return rnd << PAGE_SHIFT; } -static unsigned long mmap_base(void) +static unsigned long mmap_base(unsigned long rnd) { unsigned long gap = rlimit(RLIMIT_STACK); @@ -91,19 +90,19 @@ static unsigned long mmap_base(void) else if (gap > MAX_GAP) gap = MAX_GAP; - return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd()); + return PAGE_ALIGN(TASK_SIZE - gap - rnd); } /* * 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) +static unsigned long mmap_legacy_base(unsigned long rnd) { if (mmap_is_ia32()) return TASK_UNMAPPED_BASE; else - return TASK_UNMAPPED_BASE + mmap_rnd(); + return TASK_UNMAPPED_BASE + rnd; } /* @@ -112,14 +111,19 @@ static unsigned long mmap_legacy_base(void) */ void arch_pick_mmap_layout(struct mm_struct *mm) { - mm->mmap_legacy_base = mmap_legacy_base(); - mm->mmap_base = mmap_base(); + unsigned long random_factor = 0UL; + + if (current->flags & PF_RANDOMIZE) + random_factor = mmap_rnd(); + + mm->mmap_legacy_base = mmap_legacy_base(random_factor); if (mmap_is_legacy()) { 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(random_factor); mm->get_unmapped_area = arch_get_unmapped_area_topdown; mm->unmap_area = arch_unmap_area_topdown; } -- 2.8.0.rc2.1.gbe9624a