Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753881AbdFVUAt (ORCPT ); Thu, 22 Jun 2017 16:00:49 -0400 Received: from shelob.surriel.com ([96.67.55.147]:50023 "EHLO shelob.surriel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752424AbdFVUAs (ORCPT ); Thu, 22 Jun 2017 16:00:48 -0400 From: riel@redhat.com To: linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, mingo@kernel.org, will.deacon@arm.com, danielmicay@gmail.com, benh@kernel.crashing.org, hughd@google.com Subject: [PATCH 1/3] x86/mmap: properly account for stack randomization in mmap_base Date: Thu, 22 Jun 2017 16:00:31 -0400 Message-Id: <20170622200033.25714-2-riel@redhat.com> X-Mailer: git-send-email 2.9.4 In-Reply-To: <20170622200033.25714-1-riel@redhat.com> References: <20170622200033.25714-1-riel@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1513 Lines: 45 From: Rik van Riel When RLIMIT_STACK is, for example, 256MB, the current code results in a gap between the top of the task and mmap_base of 256MB, failing to take into account the amount by which the stack address was randomized. In other words, the stack gets less than RLIMIT_STACK space. Ensure that the gap between the stack and mmap_base always takes stack randomization and the stack guard gap into account. >From Daniel Micay's linux-hardened tree. Reported-by: Florian Weimer Signed-off-by: Daniel Micay Signed-off-by: Rik van Riel --- arch/x86/mm/mmap.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 19ad095b41df..7c35dd73dbd4 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -95,13 +95,18 @@ unsigned long arch_mmap_rnd(void) static unsigned long mmap_base(unsigned long rnd, unsigned long task_size) { unsigned long gap = rlimit(RLIMIT_STACK); + unsigned long pad = stack_maxrandom_size(task_size) + stack_guard_gap; unsigned long gap_min, gap_max; + /* Values close to RLIM_INFINITY can overflow. */ + if (gap + pad > gap) + gap += pad; + /* * Top of mmap area (just below the process stack). * Leave an at least ~128 MB hole with possible stack randomization. */ - gap_min = SIZE_128M + stack_maxrandom_size(task_size); + gap_min = SIZE_128M; gap_max = (task_size / 6) * 5; if (gap < gap_min) -- 2.9.4