From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756257AbbJ1V0L (ORCPT ); Wed, 28 Oct 2015 17:26:11 -0400 Received: from mail-pa0-f54.google.com ([209.85.220.54]:35839 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756209AbbJ1V0I (ORCPT ); Wed, 28 Oct 2015 17:26:08 -0400 From: Daniel Cashman To: linux-kernel@vger.kernel.org Cc: linux@arm.linux.org.uk, akpm@linux-foundation.org, keescook@chromium.org, mingo@kernel.org, linux-arm-kernel@lists.infradead.org, corbet@lwn.net, dzickus@redhat.com, ebiederm@xmission.com, xypron.glpk@gmx.de, jpoimboe@redhat.com, kirill.shutemov@linux.intel.com, n-horiguchi@ah.jp.nec.com, aarcange@redhat.com, mgorman@suse.de, tglx@linutronix.de, rientjes@google.com, linux-mm@kvack.org, linux-doc@vger.kernel.org, salyzyn@android.com, jeffv@google.com, nnk@google.com, dcashman Subject: [PATCH 1/2] mm: mmap: Add new /proc tunable for mmap_base ASLR. Date: Wed, 28 Oct 2015 14:25:19 -0700 Message-Id: <1446067520-31806-1-git-send-email-dcashman@android.com> X-Mailer: git-send-email 2.6.0.rc2.230.g3dd15c0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: dcashman ASLR currently only uses 8 bits to generate the random offset for the mmap base address on 32 bit architectures. This value was chosen to prevent a poorly chosen value from dividing the address space in such a way as to prevent large allocations. This may not be an issue on all platforms. Allow the specification of a minimum number of bits so that platforms desiring greater ASLR protection may determine where to place the trade-off. Signed-off-by: Daniel Cashman --- Documentation/sysctl/kernel.txt | 14 ++++++++++++++ include/linux/mm.h | 6 ++++++ kernel/sysctl.c | 11 +++++++++++ 3 files changed, 31 insertions(+) diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 6fccb69..0d4ca53 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -41,6 +41,7 @@ show up in /proc/sys/kernel: - kptr_restrict - kstack_depth_to_print [ X86 only ] - l2cr [ PPC only ] +- mmap_rnd_bits - modprobe ==> Documentation/debugging-modules.txt - modules_disabled - msg_next_id [ sysv ipc ] @@ -391,6 +392,19 @@ This flag controls the L2 cache of G3 processor boards. If ============================================================== +mmap_rnd_bits: + +This value can be used to select the number of bits to use to +determine the random offset to the base address of vma regions +resulting from mmap allocations on architectures which support +tuning address space randomization. This value will be bounded +by the architecture's minimum and maximum supported values. + +This value can be changed after boot using the +/proc/sys/kernel/mmap_rnd_bits tunable + +============================================================== + modules_disabled: A toggle value indicating if modules are allowed to be loaded diff --git a/include/linux/mm.h b/include/linux/mm.h index 80001de..15b083a 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -51,6 +51,12 @@ extern int sysctl_legacy_va_layout; #define sysctl_legacy_va_layout 0 #endif +#ifdef CONFIG_ARCH_MMAP_RND_BITS +extern int mmap_rnd_bits_min; +extern int mmap_rnd_bits_max; +extern int mmap_rnd_bits; +#endif + #include #include #include diff --git a/kernel/sysctl.c b/kernel/sysctl.c index e69201d..37e657a 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1139,6 +1139,17 @@ static struct ctl_table kern_table[] = { .proc_handler = timer_migration_handler, }, #endif +#ifdef CONFIG_ARCH_MMAP_RND_BITS + { + .procname = "mmap_rnd_bits", + .data = &mmap_rnd_bits, + .maxlen = sizeof(mmap_rnd_bits), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = &mmap_rnd_bits_min, + .extra2 = &mmap_rnd_bits_max, + }, +#endif { } }; -- 2.6.0.rc2.230.g3dd15c0