The patch titled
Subject: x86: fortify: kmsan: fix KMSAN fortify builds
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
x86-fortify-kmsan-fix-kmsan-fortify-builds.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/x86-fortify-kmsan-fix-kmsan-fortify-builds.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Alexander Potapenko <glider@xxxxxxxxxx>
Subject: x86: fortify: kmsan: fix KMSAN fortify builds
Date: Mon, 24 Oct 2022 23:21:44 +0200
Ensure that KMSAN builds replace memset/memcpy/memmove calls with the
respective __msan_XXX functions, and that none of the macros are redefined
twice. This should allow building kernel with both CONFIG_KMSAN and
CONFIG_FORTIFY_SOURCE.
Link: https://lkml.kernel.org/r/20221024212144.2852069-5-glider@xxxxxxxxxx
Link: https://github.com/google/kmsan/issues/89
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Reported-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>
Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/string_64.h | 11 +++++++----
include/linux/fortify-string.h | 17 +++++++++++++++--
include/linux/kmsan_string.h | 21 +++++++++++++++++++++
mm/kmsan/instrumentation.c | 1 +
4 files changed, 44 insertions(+), 6 deletions(-)
--- a/arch/x86/include/asm/string_64.h~x86-fortify-kmsan-fix-kmsan-fortify-builds
+++ a/arch/x86/include/asm/string_64.h
@@ -10,10 +10,13 @@
/* Even with __builtin_ the compiler may decide to use the out of line
function. */
+#if defined(__SANITIZE_MEMORY__) && defined(__NO_FORTIFY)
+#include <linux/kmsan_string.h>
+#endif
+
#define __HAVE_ARCH_MEMCPY 1
-#if defined(__SANITIZE_MEMORY__)
+#if defined(__SANITIZE_MEMORY__) && defined(__NO_FORTIFY)
#undef memcpy
-void *__msan_memcpy(void *dst, const void *src, size_t size);
#define memcpy __msan_memcpy
#else
extern void *memcpy(void *to, const void *from, size_t len);
@@ -21,7 +24,7 @@ extern void *memcpy(void *to, const void
extern void *__memcpy(void *to, const void *from, size_t len);
#define __HAVE_ARCH_MEMSET
-#if defined(__SANITIZE_MEMORY__)
+#if defined(__SANITIZE_MEMORY__) && defined(__NO_FORTIFY)
extern void *__msan_memset(void *s, int c, size_t n);
#undef memset
#define memset __msan_memset
@@ -67,7 +70,7 @@ static inline void *memset64(uint64_t *s
}
#define __HAVE_ARCH_MEMMOVE
-#if defined(__SANITIZE_MEMORY__)
+#if defined(__SANITIZE_MEMORY__) && defined(__NO_FORTIFY)
#undef memmove
void *__msan_memmove(void *dest, const void *src, size_t len);
#define memmove __msan_memmove
--- a/include/linux/fortify-string.h~x86-fortify-kmsan-fix-kmsan-fortify-builds
+++ a/include/linux/fortify-string.h
@@ -43,11 +43,24 @@ extern __kernel_size_t __underlying_strl
extern char *__underlying_strncat(char *p, const char *q, __kernel_size_t count) __RENAME(strncat);
extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size) __RENAME(strncpy);
#else
-#define __underlying_memchr __builtin_memchr
-#define __underlying_memcmp __builtin_memcmp
+
+#if defined(__SANITIZE_MEMORY__)
+/*
+ * For KMSAN builds all memcpy/memset/memmove calls should be replaced by the
+ * corresponding __msan_XXX functions.
+ */
+#include <linux/kmsan_string.h>
+#define __underlying_memcpy __msan_memcpy
+#define __underlying_memmove __msan_memmove
+#define __underlying_memset __msan_memset
+#else
#define __underlying_memcpy __builtin_memcpy
#define __underlying_memmove __builtin_memmove
#define __underlying_memset __builtin_memset
+#endif
+
+#define __underlying_memchr __builtin_memchr
+#define __underlying_memcmp __builtin_memcmp
#define __underlying_strcat __builtin_strcat
#define __underlying_strcpy __builtin_strcpy
#define __underlying_strlen __builtin_strlen
--- /dev/null
+++ a/include/linux/kmsan_string.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * KMSAN string functions API used in other headers.
+ *
+ * Copyright (C) 2022 Google LLC
+ * Author: Alexander Potapenko <glider@xxxxxxxxxx>
+ *
+ */
+#ifndef _LINUX_KMSAN_STRING_H
+#define _LINUX_KMSAN_STRING_H
+
+/*
+ * KMSAN overrides the default memcpy/memset/memmove implementations in the
+ * kernel, which requires having __msan_XXX function prototypes in several other
+ * headers. Keep them in one place instead of open-coding.
+ */
+void *__msan_memcpy(void *dst, const void *src, size_t size);
+void *__msan_memset(void *s, int c, size_t n);
+void *__msan_memmove(void *dest, const void *src, size_t len);
+
+#endif /* _LINUX_KMSAN_STRING_H */
--- a/mm/kmsan/instrumentation.c~x86-fortify-kmsan-fix-kmsan-fortify-builds
+++ a/mm/kmsan/instrumentation.c
@@ -14,6 +14,7 @@
#include "kmsan.h"
#include <linux/gfp.h>
+#include <linux/kmsan_string.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
_
Patches currently in -mm which might be from glider@xxxxxxxxxx are
mm-kmsan-export-kmsan_copy_page_meta.patch
x86-purgatory-disable-kmsan-instrumentation.patch
kconfigdebug-disable-config_frame_warn-for-kmsan-by-default.patch
x86-asm-make-sure-__put_user_size-evaluates-pointer-once.patch
x86-fortify-kmsan-fix-kmsan-fortify-builds.patch
