From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f47.google.com (mail-pa0-f47.google.com [209.85.220.47]) by kanga.kvack.org (Postfix) with ESMTP id 33ED782F64 for ; Wed, 28 Oct 2015 17:26:09 -0400 (EDT) Received: by padhy1 with SMTP id hy1so11903917pad.0 for ; Wed, 28 Oct 2015 14:26:09 -0700 (PDT) Received: from mail-pa0-x22e.google.com (mail-pa0-x22e.google.com. [2607:f8b0:400e:c03::22e]) by mx.google.com with ESMTPS id rp16si72969751pab.8.2015.10.28.14.26.08 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 28 Oct 2015 14:26:08 -0700 (PDT) Received: by padhy1 with SMTP id hy1so11903694pad.0 for ; Wed, 28 Oct 2015 14:26:08 -0700 (PDT) From: Daniel Cashman 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org