From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751701AbdAaUcU (ORCPT ); Tue, 31 Jan 2017 15:32:20 -0500 Received: from mail-pf0-f179.google.com ([209.85.192.179]:34574 "EHLO mail-pf0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751507AbdAaUcB (ORCPT ); Tue, 31 Jan 2017 15:32:01 -0500 From: Kees Cook To: linux-kernel@vger.kernel.org Cc: Kees Cook , Emese Revfy , Arnd Bergmann , Josh Triplett , pageexec@freemail.hu, yamada.masahiro@socionext.com, minipli@ld-linux.so, linux@armlinux.org.uk, catalin.marinas@arm.com, linux@rasmusvillemoes.dk, david.brown@linaro.org, benh@kernel.crashing.org, tglx@linutronix.de, akpm@linux-foundation.org, jlayton@poochiereds.net, sam@ravnborg.org, kernel-hardening@lists.openwall.com Subject: [PATCH v5 4/4] initify: Mark functions with the __unverified_nocapture attribute Date: Tue, 31 Jan 2017 12:24:22 -0800 Message-Id: <1485894263-91051-5-git-send-email-keescook@chromium.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1485894263-91051-1-git-send-email-keescook@chromium.org> References: <1485894263-91051-1-git-send-email-keescook@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Emese Revfy The initify plugin attempts to analyze function arguments that have been marked correctly with the __nocapture attribute. However, due to code complexity, this is not always possible to verify. As a result, some __nocapture attributes need to be marked as excluded from the automatic verification. To do this, the __unverified_nocapture attribute is added. It is intedned to only be used on function parameters that are difficult for the plugin to analyze. Signed-off-by: Emese Revfy Signed-off-by: Kees Cook --- include/linux/compiler-gcc.h | 8 ++++++++ include/linux/compiler.h | 4 ++++ lib/vsprintf.c | 4 ++-- 3 files changed, 14 insertions(+), 2 deletions(-) diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index cd4e9ffb00a7..fc0495e849ff 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -204,9 +204,17 @@ * been unmapped from memory. In order to identify functions that are confirmed * to not capture their arguments, the __nocapture() attribute is used so that * initify can better identify candidate variables. + * + * Arguments marked in this way are verified by the plugin, but sometimes + * code complexity and other limitiations will cause initify to not be able + * to check it correctly. For these cases, the __unverified_nocapture + * attribute can be added to disable this checking, overriding the plugin + * logic for cases that have been manually verified. This should not need + * to be used very often. */ #ifdef INITIFY_PLUGIN #define __nocapture(...) __attribute__((nocapture(__VA_ARGS__))) +#define __unverified_nocapture(...) __attribute__((unverified_nocapture(__VA_ARGS__))) #endif /* diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 8b3dcc790bb6..1bde420f07bb 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -437,6 +437,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s # define __nocapture(...) #endif +#ifndef __unverified_nocapture +# define __unverified_nocapture(...) +#endif + /* * Tell gcc if a function is cold. The compiler will assume any path * directly leading to the call is unlikely. diff --git a/lib/vsprintf.c b/lib/vsprintf.c index a192761d338a..cb964b51f9f8 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -118,7 +118,7 @@ long long simple_strtoll(const char *cp, char **endp, unsigned int base) } EXPORT_SYMBOL(simple_strtoll); -static noinline_for_stack __nocapture(1) +static noinline_for_stack __nocapture(1) __unverified_nocapture(1) int skip_atoi(const char **s) { int i = 0; @@ -1570,7 +1570,7 @@ int kptr_restrict __read_mostly; * function pointers are really function descriptors, which contain a * pointer to the real address. */ -static noinline_for_stack __nocapture(1) +static noinline_for_stack __nocapture(1) __unverified_nocapture(1) char *pointer(const char *fmt, char *buf, char *end, void *ptr, struct printf_spec spec) { -- 2.7.4