From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kees Cook Subject: [PATCH v3 0/8] introduce post-init read-only memory Date: Wed, 9 Dec 2015 13:43:16 -0800 Message-ID: <1449697404-21076-1-git-send-email-keescook@chromium.org> Reply-To: kernel-hardening@lists.openwall.com Return-path: List-Post: List-Help: List-Unsubscribe: List-Subscribe: To: linux-kernel@vger.kernel.org Cc: Kees Cook , Ingo Molnar , Andy Lutomirski , "H. Peter Anvin" , Michael Ellerman , Mathias Krause , Thomas Gleixner , x86@kernel.org, Arnd Bergmann , PaX Team , Emese Revfy , kernel-hardening@lists.openwall.com, linux-arch List-Id: linux-arch.vger.kernel.org One of the easiest ways to protect the kernel from attack is to reduce the internal attack surface exposed when a "write" flaw is available. By making as much of the kernel read-only as possible, we reduce the attack surface. Many things are written to only during __init, and never changed again. These cannot be made "const" since the compiler will do the wrong thing (we do actually need to write to them). Instead, move these items into a memory region that will be made read-only during mark_rodata_ro() which happens after all kernel __init code has finished. This introduces __ro_after_init as a way to mark such memory, and uses it on the x86 vDSO to kill an extant kernel exploitation method. Also adds a new kernel parameter to help debug future use and adds an lkdtm test to check the results. -Kees v3: - conslidated mark_rodata_ro() - make CONFIG_DEBUG_RODATA always enabled on x86, mingo - enhanced strtobool and potential callers to use "on"/"off" - use strtobool for rodata= param, gregkh v2: - renamed __read_only to __ro_after_init From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.outflux.net ([198.145.64.163]:43258 "EHLO smtp.outflux.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753703AbbLIVoV (ORCPT ); Wed, 9 Dec 2015 16:44:21 -0500 From: Kees Cook Subject: [PATCH v3 0/8] introduce post-init read-only memory Date: Wed, 9 Dec 2015 13:43:16 -0800 Message-ID: <1449697404-21076-1-git-send-email-keescook@chromium.org> Sender: linux-arch-owner@vger.kernel.org List-ID: To: linux-kernel@vger.kernel.org Cc: Kees Cook , Ingo Molnar , Andy Lutomirski , "H. Peter Anvin" , Michael Ellerman , Mathias Krause , Thomas Gleixner , x86@kernel.org, Arnd Bergmann , PaX Team , Emese Revfy , kernel-hardening@lists.openwall.com, linux-arch Message-ID: <20151209214316.PIKY5_pITJjM_BMEcbJZy7JCKCRU7_U6D_A9wg5sPJ8@z> One of the easiest ways to protect the kernel from attack is to reduce the internal attack surface exposed when a "write" flaw is available. By making as much of the kernel read-only as possible, we reduce the attack surface. Many things are written to only during __init, and never changed again. These cannot be made "const" since the compiler will do the wrong thing (we do actually need to write to them). Instead, move these items into a memory region that will be made read-only during mark_rodata_ro() which happens after all kernel __init code has finished. This introduces __ro_after_init as a way to mark such memory, and uses it on the x86 vDSO to kill an extant kernel exploitation method. Also adds a new kernel parameter to help debug future use and adds an lkdtm test to check the results. -Kees v3: - conslidated mark_rodata_ro() - make CONFIG_DEBUG_RODATA always enabled on x86, mingo - enhanced strtobool and potential callers to use "on"/"off" - use strtobool for rodata= param, gregkh v2: - renamed __read_only to __ro_after_init