From 36be5cba99f6f9984a9a9f0454f95a38f4184d3e Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Fri, 24 Feb 2023 09:59:40 +0100 Subject: [PATCH] kasan: treat meminstrinsic as builtins in uninstrumented files Where the compiler instruments meminstrinsics by generating calls to __asan/__hwasan_ prefixed functions, let the compiler consider memintrinsics as builtin again. To do so, never override memset/memmove/memcpy if the compiler does the correct instrumentation - even on !GENERIC_ENTRY architectures. [elver@google.com: powerpc: don't rename memintrinsics if compiler adds prefixes] Link: https://lore.kernel.org/all/20230224085942.1791837-1-elver@google.com/ [1] Link: https://lkml.kernel.org/r/20230227094726.3833247-1-elver@google.com Link: https://lkml.kernel.org/r/20230224085942.1791837-2-elver@google.com Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions") Signed-off-by: Marco Elver Reviewed-by: Andrey Konovalov Tested-by: Linux Kernel Functional Testing Tested-by: Naresh Kamboju Acked-by: Michael Ellerman (powerpc) Cc: Alexander Potapenko Cc: Andrey Ryabinin Cc: Borislav Petkov (AMD) Cc: Dave Hansen Cc: Dmitry Vyukov Cc: Ingo Molnar Cc: Jakub Jelinek Cc: Kees Cook Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Nicolas Schier Cc: Peter Zijlstra (Intel) Cc: Thomas Gleixner Cc: Vincenzo Frascino Signed-off-by: Andrew Morton --- lib/Kconfig.kasan | 9 +++++++++ mm/kasan/shadow.c | 5 ++++- scripts/Makefile.kasan | 9 +++++++++ 3 files changed, 22 insertions(+), 1 deletion(-) diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan index be6ee6020290..fdca89c05745 100644 --- a/lib/Kconfig.kasan +++ b/lib/Kconfig.kasan @@ -49,6 +49,15 @@ menuconfig KASAN if KASAN +config CC_HAS_KASAN_MEMINTRINSIC_PREFIX + def_bool (CC_IS_CLANG && $(cc-option,-fsanitize=kernel-address -mllvm -asan-kernel-mem-intrinsic-prefix=1)) || \ + (CC_IS_GCC && $(cc-option,-fsanitize=kernel-address --param asan-kernel-mem-intrinsic-prefix=1)) + # Don't define it if we don't need it: compilation of the test uses + # this variable to decide how the compiler should treat builtins. + depends on !KASAN_HW_TAGS + help + The compiler is able to prefix memintrinsics with __asan or __hwasan. + choice prompt "KASAN mode" default KASAN_GENERIC diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c index 90186122b21b..c8b86f3273b5 100644 --- a/mm/kasan/shadow.c +++ b/mm/kasan/shadow.c @@ -38,11 +38,14 @@ bool __kasan_check_write(const volatile void *p, unsigned int size) } EXPORT_SYMBOL(__kasan_check_write); -#ifndef CONFIG_GENERIC_ENTRY +#if !defined(CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX) && !defined(CONFIG_GENERIC_ENTRY) /* * CONFIG_GENERIC_ENTRY relies on compiler emitted mem*() calls to not be * instrumented. KASAN enabled toolchains should emit __asan_mem*() functions * for the sites they want to instrument. + * + * If we have a compiler that can instrument meminstrinsics, never override + * these, so that non-instrumented files can safely consider them as builtins. */ #undef memset void *memset(void *addr, int c, size_t len) diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan index fa9f836f8039..c186110ffa20 100644 --- a/scripts/Makefile.kasan +++ b/scripts/Makefile.kasan @@ -1,5 +1,14 @@ # SPDX-License-Identifier: GPL-2.0 + +ifdef CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX +# Safe for compiler to generate meminstrinsic calls in uninstrumented files. +CFLAGS_KASAN_NOSANITIZE := +else +# Don't let compiler generate memintrinsic calls in uninstrumented files +# because they are instrumented. CFLAGS_KASAN_NOSANITIZE := -fno-builtin +endif + KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET) cc-param = $(call cc-option, -mllvm -$(1), $(call cc-option, --param $(1)))