Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751857AbdCZVJn (ORCPT ); Sun, 26 Mar 2017 17:09:43 -0400 Received: from olympus.edkovsky.org ([72.14.187.238]:42262 "EHLO edkovsky.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751823AbdCZVJZ (ORCPT ); Sun, 26 Mar 2017 17:09:25 -0400 From: Eddie Kovsky To: jeyu@redhat.com, rusty@rustcorp.com.au, keescook@chromium.org Cc: linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: [PATCH v4 2/2] extable: verify address is read-only Date: Sun, 26 Mar 2017 15:08:25 -0600 Message-Id: <20170326210825.23255-3-ewk@edkovsky.org> X-Mailer: git-send-email 2.12.1 In-Reply-To: <20170326210825.23255-1-ewk@edkovsky.org> References: <20170326210825.23255-1-ewk@edkovsky.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2413 Lines: 78 Provide a mechanism to check if the address of a variable is const or ro_after_init. It mimics the existing functions that test if an address is inside the kernel's text section. The idea is to prevent structures that are not read-only from being passed to functions. Other functions inside the kernel could then use this capability to verify that their arguments are read-only. This implements the first half of a suggestion made by Kees Cook for the Kernel Self Protection Project: - provide mechanism to check for ro_after_init memory areas, and reject structures not marked ro_after_init in vmbus_register() Suggested-by: Kees Cook Signed-off-by: Eddie Kovsky --- Changes in v4: - Rename function core_kernel_ro_data() to core_kernel_rodata(). Changes in v3: - Fix missing declaration of is_module_rodata_address() --- include/linux/kernel.h | 2 ++ kernel/extable.c | 29 +++++++++++++++++++++++++++++ 2 files changed, 31 insertions(+) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 4c26dc3a8295..5748784ca209 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -444,6 +444,8 @@ extern int core_kernel_data(unsigned long addr); extern int __kernel_text_address(unsigned long addr); extern int kernel_text_address(unsigned long addr); extern int func_ptr_is_kernel_text(void *ptr); +extern int core_kernel_rodata(unsigned long addr); +extern int kernel_ro_address(unsigned long addr); unsigned long int_sqrt(unsigned long); diff --git a/kernel/extable.c b/kernel/extable.c index 2676d7f8baf6..22562cfc6ac3 100644 --- a/kernel/extable.c +++ b/kernel/extable.c @@ -154,3 +154,32 @@ int func_ptr_is_kernel_text(void *ptr) return 1; return is_module_text_address(addr); } + +/** + * core_kernel_rodata - Verify address points to read-only section + * @addr: address to test + * + */ +int core_kernel_rodata(unsigned long addr) +{ + if (addr >= (unsigned long)__start_rodata && + addr < (unsigned long)__end_rodata) + return 1; + + if (addr >= (unsigned long)__start_data_ro_after_init && + addr < (unsigned long)__end_data_ro_after_init) + return 1; + + return 0; +} + +/* Verify that address is const or ro_after_init. */ +int kernel_ro_address(unsigned long addr) +{ + if (core_kernel_rodata(addr)) + return 1; + if (is_module_rodata_address(addr)) + return 1; + + return 0; +} -- 2.12.1