From patchwork Wed Jun 20 22:09:29 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Rick Edgecombe X-Patchwork-Id: 10478787 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 99B7C600F6 for ; Wed, 20 Jun 2018 22:12:45 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8D0AB2883A for ; Wed, 20 Jun 2018 22:12:45 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 81D9729121; Wed, 20 Jun 2018 22:12:45 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id A14822883A for ; Wed, 20 Jun 2018 22:12:44 +0000 (UTC) Received: (qmail 12162 invoked by uid 550); 20 Jun 2018 22:12:25 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Delivered-To: moderator for kernel-hardening@lists.openwall.com Received: (qmail 9594 invoked from network); 20 Jun 2018 22:09:45 -0000 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,249,1526367600"; d="scan'208";a="66312716" From: Rick Edgecombe To: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-hardening@lists.openwall.com Cc: kristen.c.accardi@intel.com, dave.hansen@intel.com, arjan.van.de.ven@intel.com, Rick Edgecombe Subject: [PATCH 2/3] x86/modules: Increase randomization for modules Date: Wed, 20 Jun 2018 15:09:29 -0700 Message-Id: <1529532570-21765-3-git-send-email-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1529532570-21765-1-git-send-email-rick.p.edgecombe@intel.com> References: <1529532570-21765-1-git-send-email-rick.p.edgecombe@intel.com> X-Virus-Scanned: ClamAV using ClamSMTP This changes the behavior of the KASLR logic for allocating memory for the text sections of loadable modules. It randomizes the location of each module text section with about 18 bits of entropy in typical use. This is enabled on X86_64 only. For 32 bit, the behavior is unchanged. The algorithm evenly breaks the module space in two, a random area and a backup area. For module text allocations, it first tries to allocate up to 10 randomly located starting pages inside the random section. If this fails, it will allocate in the backup area. The backup area base will be offset in the same way as the current algorithm does for the base area, 1024 possible locations. Signed-off-by: Rick Edgecombe --- arch/x86/include/asm/pgtable_64_types.h | 1 + arch/x86/kernel/module.c | 80 ++++++++++++++++++++++++++++++--- 2 files changed, 76 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h index 054765a..a98708a 100644 --- a/arch/x86/include/asm/pgtable_64_types.h +++ b/arch/x86/include/asm/pgtable_64_types.h @@ -141,6 +141,7 @@ extern unsigned int ptrs_per_p4d; /* The module sections ends with the start of the fixmap */ #define MODULES_END _AC(0xffffffffff000000, UL) #define MODULES_LEN (MODULES_END - MODULES_VADDR) +#define MODULES_RAND_LEN (MODULES_LEN/2) #define ESPFIX_PGD_ENTRY _AC(-2, UL) #define ESPFIX_BASE_ADDR (ESPFIX_PGD_ENTRY << P4D_SHIFT) diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c index f58336a..833ea81 100644 --- a/arch/x86/kernel/module.c +++ b/arch/x86/kernel/module.c @@ -77,6 +77,71 @@ static unsigned long int get_module_load_offset(void) } #endif +static unsigned long get_module_area_base(void) +{ + return MODULES_VADDR + get_module_load_offset(); +} + +#if defined(CONFIG_X86_64) && defined(CONFIG_RANDOMIZE_BASE) +static unsigned long get_module_vmalloc_start(void) +{ + if (kaslr_enabled()) + return MODULES_VADDR + MODULES_RAND_LEN + + get_module_load_offset(); + else + return get_module_area_base(); +} + +static void *try_module_alloc(unsigned long addr, unsigned long size) +{ + return __vmalloc_node_try_addr(addr, size, GFP_KERNEL, + PAGE_KERNEL_EXEC, 0, + NUMA_NO_NODE, + __builtin_return_address(0)); +} + +/* + * Try to allocate in 10 random positions starting in the random part of the + * module space. If these fail, return NULL. + */ +static void *try_module_randomize_each(unsigned long size) +{ + void *p = NULL; + unsigned int i; + unsigned long offset; + unsigned long addr; + unsigned long end; + const unsigned long nr_mod_positions = MODULES_RAND_LEN / MODULE_ALIGN; + + if (!kaslr_enabled()) + return NULL; + + for (i = 0; i < 10; i++) { + offset = (get_random_long() % nr_mod_positions) * MODULE_ALIGN; + addr = (unsigned long)MODULES_VADDR + offset; + end = addr + size; + + if (end > addr && end < MODULES_END) { + p = try_module_alloc(addr, size); + + if (p) + return p; + } + } + return NULL; +} +#else +static unsigned long get_module_vmalloc_start(void) +{ + return get_module_area_base(); +} + +static void *try_module_randomize_each(unsigned long size) +{ + return NULL; +} +#endif + void *module_alloc(unsigned long size) { void *p; @@ -84,11 +149,16 @@ void *module_alloc(unsigned long size) if (PAGE_ALIGN(size) > MODULES_LEN) return NULL; - p = __vmalloc_node_range(size, MODULE_ALIGN, - MODULES_VADDR + get_module_load_offset(), - MODULES_END, GFP_KERNEL, - PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE, - __builtin_return_address(0)); + p = try_module_randomize_each(size); + + if (!p) + p = __vmalloc_node_range(size, MODULE_ALIGN, + get_module_vmalloc_start(), + MODULES_END, GFP_KERNEL, + PAGE_KERNEL_EXEC, 0, + NUMA_NO_NODE, + __builtin_return_address(0)); + if (p && (kasan_module_alloc(p, size) < 0)) { vfree(p); return NULL;