Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757403AbbEVJBD (ORCPT ); Fri, 22 May 2015 05:01:03 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:35460 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757386AbbEVJAv (ORCPT ); Fri, 22 May 2015 05:00:51 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: "David S. Miller" , Anton Blanchard , Benjamin Herrenschmidt , Yann Droneaud , Will Deacon , =?UTF-8?q?Moritz=20M=C3=BChlenhoff?= , Luis Henriques Subject: [PATCH 3.16.y-ckt 126/129] arm64/mm: Remove hack in mmap randomize layout Date: Fri, 22 May 2015 09:58:31 +0100 Message-Id: <1432285114-9254-127-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1432285114-9254-1-git-send-email-luis.henriques@canonical.com> References: <1432285114-9254-1-git-send-email-luis.henriques@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2651 Lines: 73 3.16.7-ckt12 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Yann Droneaud commit d6c763afab142a85e4770b4bc2a5f40f256d5c5d upstream. Since commit 8a0a9bd4db63 ('random: make get_random_int() more random'), get_random_int() returns a random value for each call, so comment and hack introduced in mmap_rnd() as part of commit 1d18c47c735e ('arm64: MMU fault handling and page table management') are incorrects. Commit 1d18c47c735e seems to use the same hack introduced by commit a5adc91a4b44 ('powerpc: Ensure random space between stack and mmaps'), latter copied in commit 5a0efea09f42 ('sparc64: Sharpen address space randomization calculations.'). But both architectures were cleaned up as part of commit fa8cbaaf5a68 ('powerpc+sparc64/mm: Remove hack in mmap randomize layout') as hack is no more needed since commit 8a0a9bd4db63. So the present patch removes the comment and the hack around get_random_int() on AArch64's mmap_rnd(). Cc: David S. Miller Cc: Anton Blanchard Cc: Benjamin Herrenschmidt Acked-by: Will Deacon Acked-by: Dan McGee Signed-off-by: Yann Droneaud Signed-off-by: Will Deacon Cc: Moritz Mühlenhoff Signed-off-by: Luis Henriques --- arch/arm64/mm/mmap.c | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-) diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c index 8ed6cb1a900f..8f7ffffc63e9 100644 --- a/arch/arm64/mm/mmap.c +++ b/arch/arm64/mm/mmap.c @@ -47,22 +47,14 @@ static int mmap_is_legacy(void) return sysctl_legacy_va_layout; } -/* - * Since get_random_int() returns the same value within a 1 jiffy window, we - * will almost always get the same randomisation for the stack and mmap - * region. This will mean the relative distance between stack and mmap will be - * the same. - * - * To avoid this we can shift the randomness by 1 bit. - */ static unsigned long mmap_rnd(void) { unsigned long rnd = 0; if (current->flags & PF_RANDOMIZE) - rnd = (long)get_random_int() & (STACK_RND_MASK >> 1); + rnd = (long)get_random_int() & STACK_RND_MASK; - return rnd << (PAGE_SHIFT + 1); + return rnd << PAGE_SHIFT; } static unsigned long mmap_base(void) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/