From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751624AbaBZAfr (ORCPT ); Tue, 25 Feb 2014 19:35:47 -0500 Received: from smtp.outflux.net ([198.145.64.163]:55552 "EHLO smtp.outflux.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750764AbaBZAfp (ORCPT ); Tue, 25 Feb 2014 19:35:45 -0500 Date: Tue, 25 Feb 2014 16:34:04 -0800 From: Kees Cook To: linux-kernel@vger.kernel.org Cc: Andrew Morton , "H. Peter Anvin" , Rob Landley , Thomas Gleixner , Ingo Molnar , x86@kernel.org, Jianguo Wu , Andy Honig , David Rientjes , linux-doc@vger.kernel.org Subject: [PATCH v2] x86, kaslr: randomize module base load address Message-ID: <20140226003403.GA26737@www.outflux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-HELO: www.outflux.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Randomize the load address of modules in the kernel to make kASLR effective for modules. Modules can only be loaded within a particular range of virtual address space. This patch adds 10 bits of entropy to the load address by adding 1-1024 * PAGE_SIZE to the beginning range where modules are loaded. Example kASLR boot without this change, with a single module loaded: ---[ Modules ]--- 0xffffffffc0000000-0xffffffffc0001000 4K ro GLB x pte 0xffffffffc0001000-0xffffffffc0002000 4K ro GLB NX pte 0xffffffffc0002000-0xffffffffc0004000 8K RW GLB NX pte 0xffffffffc0004000-0xffffffffc0200000 2032K pte 0xffffffffc0200000-0xffffffffff000000 1006M pmd ---[ End Modules ]--- Example kASLR boot after this change, same module loaded: ---[ Modules ]--- 0xffffffffc0000000-0xffffffffc0200000 2M pmd 0xffffffffc0200000-0xffffffffc03bf000 1788K pte 0xffffffffc03bf000-0xffffffffc03c0000 4K ro GLB x pte 0xffffffffc03c0000-0xffffffffc03c1000 4K ro GLB NX pte 0xffffffffc03c1000-0xffffffffc03c3000 8K RW GLB NX pte 0xffffffffc03c3000-0xffffffffc0400000 244K pte 0xffffffffc0400000-0xffffffffff000000 1004M pmd ---[ End Modules ]--- Signed-off-by: Andy Honig Signed-off-by: Kees Cook --- v2: - add update to Documentation/kernel-parameters.txt; akpm. --- Documentation/kernel-parameters.txt | 4 ++-- arch/x86/kernel/module.c | 43 ++++++++++++++++++++++++++++++++--- 2 files changed, 42 insertions(+), 5 deletions(-) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 7116fda7077f..580a60cabd9b 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2053,8 +2053,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted. IOAPICs that may be present in the system. nokaslr [X86] - Disable kernel base offset ASLR (Address Space - Layout Randomization) if built into the kernel. + Disable kernel and module base offset ASLR (Address + Space Layout Randomization) if built into the kernel. noautogroup Disable scheduler automatic task group creation. diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c index 18be189368bb..49483137371f 100644 --- a/arch/x86/kernel/module.c +++ b/arch/x86/kernel/module.c @@ -28,6 +28,7 @@ #include #include #include +#include #include #include @@ -43,13 +44,49 @@ do { \ } while (0) #endif +#ifdef CONFIG_RANDOMIZE_BASE +static unsigned long module_load_offset; +static int randomize_modules = 1; + +static int __init parse_nokaslr(char *p) +{ + randomize_modules = 0; + return 0; +} +early_param("nokaslr", parse_nokaslr); + +static unsigned long int get_module_load_offset(void) +{ + if (randomize_modules) { + mutex_lock(&module_mutex); + /* + * Calculate the module_load_offset the first time this + * code is called. Once calculated it stays the same until + * reboot. + */ + if (module_load_offset == 0) + module_load_offset = + (get_random_int() % 1024 + 1) * PAGE_SIZE; + mutex_unlock(&module_mutex); + } + return module_load_offset; +} +#else +static unsigned long int get_module_load_offset(void) +{ + return 0; +} +#endif + void *module_alloc(unsigned long size) { if (PAGE_ALIGN(size) > MODULES_LEN) return NULL; - return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END, - GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC, - NUMA_NO_NODE, __builtin_return_address(0)); + return __vmalloc_node_range(size, 1, + MODULES_VADDR + get_module_load_offset(), + MODULES_END, GFP_KERNEL | __GFP_HIGHMEM, + PAGE_KERNEL_EXEC, NUMA_NO_NODE, + __builtin_return_address(0)); } #ifdef CONFIG_X86_32 -- 1.7.9.5 -- Kees Cook Chrome OS Security