Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933412AbbG1KHN (ORCPT ); Tue, 28 Jul 2015 06:07:13 -0400 Received: from mail-wi0-f171.google.com ([209.85.212.171]:33540 "EHLO mail-wi0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754193AbbG1Jpl (ORCPT ); Tue, 28 Jul 2015 05:45:41 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Yann Droneaud , "David S. Miller" , Anton Blanchard , Benjamin Herrenschmidt , Will Deacon , Jiri Slaby Subject: [PATCH 3.12 075/124] arm64/mm: Remove hack in mmap randomize layout Date: Tue, 28 Jul 2015 11:43:29 +0200 Message-Id: <839e7c40a4ba6e063723b87bfb96dfdb33d203cc.1438076484.git.jslaby@suse.cz> X-Mailer: git-send-email 2.4.6 In-Reply-To: <90d8a5681e4a9e320611b422f0ed012e148c2bca.1438076484.git.jslaby@suse.cz> References: <90d8a5681e4a9e320611b422f0ed012e148c2bca.1438076484.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2593 Lines: 75 From: Yann Droneaud 3.12-stable review patch. If anyone has any objections, please let me know. =============== 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 Signed-off-by: Jiri Slaby --- 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) -- 2.4.6 -- 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/