From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751214AbdFBP22 (ORCPT ); Fri, 2 Jun 2017 11:28:28 -0400 Received: from shelob.surriel.com ([96.67.55.147]:48207 "EHLO shelob.surriel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750813AbdFBP21 (ORCPT ); Fri, 2 Jun 2017 11:28:27 -0400 From: riel@redhat.com To: linux-kernel@vger.kernel.org Cc: kernel-hardening@lists.openwall.com, akpm@linux-foundation.org, mingo@kernel.org, oleg@redhat.com, lwoodman@redhat.com, mhocko@suse.de, danielmicay@gmail.com, will.deacon@arm.com, benh@kernel.crashing.org Subject: [PATCH 4/6] arm64/mmap: properly account for stack randomization in mmap_base Date: Fri, 2 Jun 2017 11:20:08 -0400 Message-Id: <20170602152010.2064-5-riel@redhat.com> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20170602152010.2064-1-riel@redhat.com> References: <20170602152010.2064-1-riel@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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/arm64/mm/mmap.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c index 7b0d55756eb1..3f15eb193e33 100644 --- a/arch/arm64/mm/mmap.c +++ b/arch/arm64/mm/mmap.c @@ -34,7 +34,7 @@ * Leave enough space between the mmap area and the stack to honour ulimit in * the face of randomisation. */ -#define MIN_GAP (SZ_128M + ((STACK_RND_MASK << PAGE_SHIFT) + 1)) +#define MIN_GAP (SZ_128M) #define MAX_GAP (STACK_TOP/6*5) static int mmap_is_legacy(void) @@ -64,6 +64,11 @@ unsigned long arch_mmap_rnd(void) static unsigned long mmap_base(unsigned long rnd) { unsigned long gap = rlimit(RLIMIT_STACK); + unsigned long pad = STACK_RND_MASK << PAGE_SHIFT; + + /* Values close to RLIM_INFINITY can overflow. */ + if (gap + pad > gap) + gap += pad; if (gap < MIN_GAP) gap = MIN_GAP; -- 2.9.3 From mboxrd@z Thu Jan 1 00:00:00 1970 From: riel@redhat.com Date: Fri, 2 Jun 2017 11:20:08 -0400 Message-Id: <20170602152010.2064-5-riel@redhat.com> In-Reply-To: <20170602152010.2064-1-riel@redhat.com> References: <20170602152010.2064-1-riel@redhat.com> Subject: [kernel-hardening] [PATCH 4/6] arm64/mmap: properly account for stack randomization in mmap_base To: linux-kernel@vger.kernel.org Cc: kernel-hardening@lists.openwall.com, akpm@linux-foundation.org, mingo@kernel.org, oleg@redhat.com, lwoodman@redhat.com, mhocko@suse.de, danielmicay@gmail.com, will.deacon@arm.com, benh@kernel.crashing.org List-ID: 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 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/arm64/mm/mmap.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c index 7b0d55756eb1..3f15eb193e33 100644 --- a/arch/arm64/mm/mmap.c +++ b/arch/arm64/mm/mmap.c @@ -34,7 +34,7 @@ * Leave enough space between the mmap area and the stack to honour ulimit in * the face of randomisation. */ -#define MIN_GAP (SZ_128M + ((STACK_RND_MASK << PAGE_SHIFT) + 1)) +#define MIN_GAP (SZ_128M) #define MAX_GAP (STACK_TOP/6*5) static int mmap_is_legacy(void) @@ -64,6 +64,11 @@ unsigned long arch_mmap_rnd(void) static unsigned long mmap_base(unsigned long rnd) { unsigned long gap = rlimit(RLIMIT_STACK); + unsigned long pad = STACK_RND_MASK << PAGE_SHIFT; + + /* Values close to RLIM_INFINITY can overflow. */ + if (gap + pad > gap) + gap += pad; if (gap < MIN_GAP) gap = MIN_GAP; -- 2.9.3