From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kees Cook Subject: [PATCH v4 0/8] introduce post-init read-only memory Date: Tue, 19 Jan 2016 10:08:34 -0800 Message-ID: <1453226922-16831-1-git-send-email-keescook@chromium.org> Reply-To: kernel-hardening@lists.openwall.com Return-path: List-Post: List-Help: List-Unsubscribe: List-Subscribe: To: Ingo Molnar Cc: Kees Cook , 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-kernel@vger.kernel.org, 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 v4: - rebased 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 mail-pf0-f179.google.com ([209.85.192.179]:35221 "EHLO mail-pf0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932579AbcASSI4 (ORCPT ); Tue, 19 Jan 2016 13:08:56 -0500 Received: by mail-pf0-f179.google.com with SMTP id 65so179161774pff.2 for ; Tue, 19 Jan 2016 10:08:56 -0800 (PST) From: Kees Cook Subject: [PATCH v4 0/8] introduce post-init read-only memory Date: Tue, 19 Jan 2016 10:08:34 -0800 Message-ID: <1453226922-16831-1-git-send-email-keescook@chromium.org> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Ingo Molnar Cc: Kees Cook , 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-kernel@vger.kernel.org, linux-arch Message-ID: <20160119180834.Y2lLweJmUFi5L5xLsOC-07obF6Z2wSUSIZgszNzD_8M@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 v4: - rebased 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