Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755774AbbKCSKM (ORCPT ); Tue, 3 Nov 2015 13:10:12 -0500 Received: from mail-pa0-f44.google.com ([209.85.220.44]:35745 "EHLO mail-pa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755718AbbKCSKJ (ORCPT ); Tue, 3 Nov 2015 13:10:09 -0500 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 v2 1/2] mm: mmap: Add new /proc tunable for mmap_base ASLR. Date: Tue, 3 Nov 2015 10:10:03 -0800 Message-Id: <1446574204-15567-1-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 Content-Length: 5430 Lines: 164 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 --- Changes in v2: - Added HAVE_ARCH_MMAP_RND_BITS as Kconfig boolean selector. - Moved ARCH_MMAP_RND_BITS_MIN, ARCH_MMAP_RND_BITS_MAX, and ARCH_MMAP_RND_BITS declarations to arch/Kconfig instead of relying soley on arch-specific Kconfigs. - Moved definition of mmap_rnd_bits_min, mmap_rnd_bits_max and mmap_rnd_bits to mm/mmap.c instead of relying solely on arch-specific code. Documentation/sysctl/kernel.txt | 14 ++++++++++++++ arch/Kconfig | 29 +++++++++++++++++++++++++++++ include/linux/mm.h | 6 ++++++ kernel/sysctl.c | 11 +++++++++++ mm/mmap.c | 6 ++++++ 5 files changed, 66 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/arch/Kconfig b/arch/Kconfig index 4e949e5..2133973 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -511,6 +511,35 @@ config ARCH_HAS_ELF_RANDOMIZE - arch_mmap_rnd() - arch_randomize_brk() +config HAVE_ARCH_MMAP_RND_BITS + bool + help + An arch should select this symbol if it supports setting a variable + number of bits for use in establishing the base address for mmap + allocations and provides values for both: + - ARCH_MMAP_RND_BITS_MIN + - ARCH_MMAP_RND_BITS_MAX + +config ARCH_MMAP_RND_BITS_MIN + int + +config ARCH_MMAP_RND_BITS_MAX + int + +config ARCH_MMAP_RND_BITS + int "Number of bits to use for ASLR of mmap base address" if EXPERT + range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX + default ARCH_MMAP_RND_BITS_MIN + depends on HAVE_ARCH_MMAP_RND_BITS + help + 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. 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 + config HAVE_COPY_THREAD_TLS bool help diff --git a/include/linux/mm.h b/include/linux/mm.h index 80001de..ee209c1 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_HAVE_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..276da8b 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_HAVE_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 { } }; diff --git a/mm/mmap.c b/mm/mmap.c index 79bcc9f..264aa8e 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -58,6 +58,12 @@ #define arch_rebalance_pgtables(addr, len) (addr) #endif +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS +int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN; +int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX; +int mmap_rnd_bits = CONFIG_ARCH_MMAP_RND_BITS; +#endif + static void unmap_region(struct mm_struct *mm, struct vm_area_struct *vma, struct vm_area_struct *prev, unsigned long start, unsigned long end); -- 2.6.0.rc2.230.g3dd15c0 -- 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/