Clang 15 provides an option to prefix memcpy/memset/memmove calls with
__asan_/__hwasan_ in instrumented functions: https://reviews.llvm.org/D122724
GCC will add support in future:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108777
Use it to regain KASAN instrumentation of memcpy/memset/memmove on
architectures that require noinstr to be really free from instrumented
mem*() functions (all GENERIC_ENTRY architectures).
Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions")
Signed-off-by: Marco Elver <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Andrey Konovalov <[email protected]>
Tested-by: Linux Kernel Functional Testing <[email protected]>
Tested-by: Naresh Kamboju <[email protected]>
---
v4:
* Also enable it for KASAN_SW_TAGS (__hwasan_mem*).
v3:
* No change.
v2:
* Use asan-kernel-mem-intrinsic-prefix=1, so that once GCC supports the
param, it also works there (it needs the =1).
The Fixes tag is just there to show the dependency, and that people
shouldn't apply this patch without 69d4c0d32186.
---
mm/kasan/kasan.h | 4 ++++
mm/kasan/shadow.c | 11 +++++++++++
scripts/Makefile.kasan | 8 ++++++++
3 files changed, 23 insertions(+)
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 71c15438afcf..172713b87556 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -637,4 +637,8 @@ void __hwasan_storeN_noabort(unsigned long addr, size_t size);
void __hwasan_tag_memory(unsigned long addr, u8 tag, unsigned long size);
+void *__hwasan_memset(void *addr, int c, size_t len);
+void *__hwasan_memmove(void *dest, const void *src, size_t len);
+void *__hwasan_memcpy(void *dest, const void *src, size_t len);
+
#endif /* __MM_KASAN_KASAN_H */
diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 98269936a5e4..f8a47cb299cb 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -107,6 +107,17 @@ void *__asan_memcpy(void *dest, const void *src, size_t len)
}
EXPORT_SYMBOL(__asan_memcpy);
+#ifdef CONFIG_KASAN_SW_TAGS
+void *__hwasan_memset(void *addr, int c, size_t len) __alias(__asan_memset);
+EXPORT_SYMBOL(__hwasan_memset);
+#ifdef __HAVE_ARCH_MEMMOVE
+void *__hwasan_memmove(void *dest, const void *src, size_t len) __alias(__asan_memmove);
+EXPORT_SYMBOL(__hwasan_memmove);
+#endif
+void *__hwasan_memcpy(void *dest, const void *src, size_t len) __alias(__asan_memcpy);
+EXPORT_SYMBOL(__hwasan_memcpy);
+#endif
+
void kasan_poison(const void *addr, size_t size, u8 value, bool init)
{
void *shadow_start, *shadow_end;
diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
index b9e94c5e7097..fa9f836f8039 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -38,6 +38,11 @@ endif
CFLAGS_KASAN += $(call cc-param,asan-stack=$(stack_enable))
+# Instrument memcpy/memset/memmove calls by using instrumented __asan_mem*()
+# instead. With compilers that don't support this option, compiler-inserted
+# memintrinsics won't be checked by KASAN on GENERIC_ENTRY architectures.
+CFLAGS_KASAN += $(call cc-param,asan-kernel-mem-intrinsic-prefix=1)
+
endif # CONFIG_KASAN_GENERIC
ifdef CONFIG_KASAN_SW_TAGS
@@ -54,6 +59,9 @@ CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
$(call cc-param,hwasan-inline-all-checks=0) \
$(instrumentation_flags)
+# Instrument memcpy/memset/memmove calls by using instrumented __hwasan_mem*().
+CFLAGS_KASAN += $(call cc-param,hwasan-kernel-mem-intrinsic-prefix=1)
+
endif # CONFIG_KASAN_SW_TAGS
export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE
--
2.39.2.637.g21b0678d19-goog
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.
Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions")
Signed-off-by: Marco Elver <[email protected]>
Reviewed-by: Andrey Konovalov <[email protected]>
Tested-by: Linux Kernel Functional Testing <[email protected]>
Tested-by: Naresh Kamboju <[email protected]>
---
v4:
* New patch.
---
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 f8a47cb299cb..43b6a59c8b54 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)))
--
2.39.2.637.g21b0678d19-goog
The tests for memset/memmove have been failing since they haven't been
instrumented in 69d4c0d32186.
Fix the test to recognize when memintrinsics aren't instrumented, and
skip test cases accordingly. We also need to conditionally pass
-fno-builtin to the test, otherwise the instrumentation pass won't
recognize memintrinsics and end up not instrumenting them either.
Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions")
Reported-by: Linux Kernel Functional Testing <[email protected]>
Signed-off-by: Marco Elver <[email protected]>
Reviewed-by: Andrey Konovalov <[email protected]>
Tested-by: Linux Kernel Functional Testing <[email protected]>
Tested-by: Naresh Kamboju <[email protected]>
---
v4:
* New patch.
---
mm/kasan/Makefile | 9 ++++++++-
mm/kasan/kasan_test.c | 29 +++++++++++++++++++++++++++++
2 files changed, 37 insertions(+), 1 deletion(-)
diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
index d4837bff3b60..7634dd2a6128 100644
--- a/mm/kasan/Makefile
+++ b/mm/kasan/Makefile
@@ -35,7 +35,14 @@ CFLAGS_shadow.o := $(CC_FLAGS_KASAN_RUNTIME)
CFLAGS_hw_tags.o := $(CC_FLAGS_KASAN_RUNTIME)
CFLAGS_sw_tags.o := $(CC_FLAGS_KASAN_RUNTIME)
-CFLAGS_KASAN_TEST := $(CFLAGS_KASAN) -fno-builtin $(call cc-disable-warning, vla)
+CFLAGS_KASAN_TEST := $(CFLAGS_KASAN) $(call cc-disable-warning, vla)
+ifndef CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX
+# If compiler instruments memintrinsics by prefixing them with __asan/__hwasan,
+# we need to treat them normally (as builtins), otherwise the compiler won't
+# recognize them as instrumentable. If it doesn't instrument them, we need to
+# pass -fno-builtin, so the compiler doesn't inline them.
+CFLAGS_KASAN_TEST += -fno-builtin
+endif
CFLAGS_kasan_test.o := $(CFLAGS_KASAN_TEST)
CFLAGS_kasan_test_module.o := $(CFLAGS_KASAN_TEST)
diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
index 74cd80c12b25..627eaf1ee1db 100644
--- a/mm/kasan/kasan_test.c
+++ b/mm/kasan/kasan_test.c
@@ -165,6 +165,15 @@ static void kasan_test_exit(struct kunit *test)
kunit_skip((test), "Test requires " #config "=n"); \
} while (0)
+#define KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test) do { \
+ if (IS_ENABLED(CONFIG_KASAN_HW_TAGS)) \
+ break; /* No compiler instrumentation. */ \
+ if (IS_ENABLED(CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX)) \
+ break; /* Should always be instrumented! */ \
+ if (IS_ENABLED(CONFIG_GENERIC_ENTRY)) \
+ kunit_skip((test), "Test requires checked mem*()"); \
+} while (0)
+
static void kmalloc_oob_right(struct kunit *test)
{
char *ptr;
@@ -454,6 +463,8 @@ static void kmalloc_oob_16(struct kunit *test)
u64 words[2];
} *ptr1, *ptr2;
+ KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
+
/* This test is specifically crafted for the generic mode. */
KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_KASAN_GENERIC);
@@ -476,6 +487,8 @@ static void kmalloc_uaf_16(struct kunit *test)
u64 words[2];
} *ptr1, *ptr2;
+ KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
+
ptr1 = kmalloc(sizeof(*ptr1), GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr1);
@@ -498,6 +511,8 @@ static void kmalloc_oob_memset_2(struct kunit *test)
char *ptr;
size_t size = 128 - KASAN_GRANULE_SIZE;
+ KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
+
ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
@@ -511,6 +526,8 @@ static void kmalloc_oob_memset_4(struct kunit *test)
char *ptr;
size_t size = 128 - KASAN_GRANULE_SIZE;
+ KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
+
ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
@@ -524,6 +541,8 @@ static void kmalloc_oob_memset_8(struct kunit *test)
char *ptr;
size_t size = 128 - KASAN_GRANULE_SIZE;
+ KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
+
ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
@@ -537,6 +556,8 @@ static void kmalloc_oob_memset_16(struct kunit *test)
char *ptr;
size_t size = 128 - KASAN_GRANULE_SIZE;
+ KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
+
ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
@@ -550,6 +571,8 @@ static void kmalloc_oob_in_memset(struct kunit *test)
char *ptr;
size_t size = 128 - KASAN_GRANULE_SIZE;
+ KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
+
ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
@@ -566,6 +589,8 @@ static void kmalloc_memmove_negative_size(struct kunit *test)
size_t size = 64;
size_t invalid_size = -2;
+ KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
+
/*
* Hardware tag-based mode doesn't check memmove for negative size.
* As a result, this test introduces a side-effect memory corruption,
@@ -590,6 +615,8 @@ static void kmalloc_memmove_invalid_size(struct kunit *test)
size_t size = 64;
size_t invalid_size = size;
+ KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
+
ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
@@ -618,6 +645,8 @@ static void kmalloc_uaf_memset(struct kunit *test)
char *ptr;
size_t size = 33;
+ KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
+
/*
* Only generic KASAN uses quarantine, which is required to avoid a
* kernel memory corruption this test causes.
--
2.39.2.637.g21b0678d19-goog
Now that memcpy/memset/memmove are no longer overridden by KASAN, we can
just use the normal symbol names in uninstrumented files.
Drop the preprocessor redefinitions.
Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions")
Signed-off-by: Marco Elver <[email protected]>
Reviewed-by: Andrey Konovalov <[email protected]>
---
v5:
* New patch.
---
arch/x86/include/asm/string_64.h | 19 -------------------
1 file changed, 19 deletions(-)
diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h
index 888731ccf1f6..c1e14cee0722 100644
--- a/arch/x86/include/asm/string_64.h
+++ b/arch/x86/include/asm/string_64.h
@@ -85,25 +85,6 @@ char *strcpy(char *dest, const char *src);
char *strcat(char *dest, const char *src);
int strcmp(const char *cs, const char *ct);
-#if (defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__))
-/*
- * For files that not instrumented (e.g. mm/slub.c) we
- * should use not instrumented version of mem* functions.
- */
-
-#undef memcpy
-#define memcpy(dst, src, len) __memcpy(dst, src, len)
-#undef memmove
-#define memmove(dst, src, len) __memmove(dst, src, len)
-#undef memset
-#define memset(s, c, n) __memset(s, c, n)
-
-#ifndef __NO_FORTIFY
-#define __NO_FORTIFY /* FORTIFY_SOURCE uses __builtin_memcpy, etc. */
-#endif
-
-#endif
-
#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
#define __HAVE_ARCH_MEMCPY_FLUSHCACHE 1
void __memcpy_flushcache(void *dst, const void *src, size_t cnt);
--
2.39.2.637.g21b0678d19-goog
Hi Marco,
On Fri, Feb 24, 2023 at 09:59:39AM +0100, Marco Elver wrote:
> Clang 15 provides an option to prefix memcpy/memset/memmove calls with
> __asan_/__hwasan_ in instrumented functions: https://reviews.llvm.org/D122724
>
> GCC will add support in future:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108777
>
> Use it to regain KASAN instrumentation of memcpy/memset/memmove on
> architectures that require noinstr to be really free from instrumented
> mem*() functions (all GENERIC_ENTRY architectures).
>
> Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions")
> Signed-off-by: Marco Elver <[email protected]>
> Acked-by: Peter Zijlstra (Intel) <[email protected]>
> Reviewed-by: Andrey Konovalov <[email protected]>
> Tested-by: Linux Kernel Functional Testing <[email protected]>
> Tested-by: Naresh Kamboju <[email protected]>
[...]
> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> index b9e94c5e7097..fa9f836f8039 100644
> --- a/scripts/Makefile.kasan
> +++ b/scripts/Makefile.kasan
> @@ -38,6 +38,11 @@ endif
>
> CFLAGS_KASAN += $(call cc-param,asan-stack=$(stack_enable))
>
> +# Instrument memcpy/memset/memmove calls by using instrumented __asan_mem*()
> +# instead. With compilers that don't support this option, compiler-inserted
> +# memintrinsics won't be checked by KASAN on GENERIC_ENTRY architectures.
> +CFLAGS_KASAN += $(call cc-param,asan-kernel-mem-intrinsic-prefix=1)
> +
> endif # CONFIG_KASAN_GENERIC
>
> ifdef CONFIG_KASAN_SW_TAGS
> @@ -54,6 +59,9 @@ CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
> $(call cc-param,hwasan-inline-all-checks=0) \
> $(instrumentation_flags)
>
> +# Instrument memcpy/memset/memmove calls by using instrumented __hwasan_mem*().
> +CFLAGS_KASAN += $(call cc-param,hwasan-kernel-mem-intrinsic-prefix=1)
This patch breaks the arm64 kernel builds with KASAN_SW_TAGS enabled and
clang prior to version 15. Those prior clang versions don't like the
'-mllvm -hwasan-kernel-mem-intrinsic-prefix=1' option, end up printing
the help text instead of generating the object.
Do we need some combination of cc-option and cc-param? Or at least
disable this instrumentation if earlier clang versions are used.
It's already in mainline as commit
51287dcb00cc715c27bf6a6b4dbd431621c5b65a.
Thanks.
--
Catalin
On Thu, 13 Apr 2023 at 16:14, Catalin Marinas <[email protected]> wrote:
>
> Hi Marco,
>
> On Fri, Feb 24, 2023 at 09:59:39AM +0100, Marco Elver wrote:
> > Clang 15 provides an option to prefix memcpy/memset/memmove calls with
> > __asan_/__hwasan_ in instrumented functions: https://reviews.llvm.org/D122724
> >
> > GCC will add support in future:
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108777
> >
> > Use it to regain KASAN instrumentation of memcpy/memset/memmove on
> > architectures that require noinstr to be really free from instrumented
> > mem*() functions (all GENERIC_ENTRY architectures).
> >
> > Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions")
> > Signed-off-by: Marco Elver <[email protected]>
> > Acked-by: Peter Zijlstra (Intel) <[email protected]>
> > Reviewed-by: Andrey Konovalov <[email protected]>
> > Tested-by: Linux Kernel Functional Testing <[email protected]>
> > Tested-by: Naresh Kamboju <[email protected]>
> [...]
> > diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> > index b9e94c5e7097..fa9f836f8039 100644
> > --- a/scripts/Makefile.kasan
> > +++ b/scripts/Makefile.kasan
> > @@ -38,6 +38,11 @@ endif
> >
> > CFLAGS_KASAN += $(call cc-param,asan-stack=$(stack_enable))
> >
> > +# Instrument memcpy/memset/memmove calls by using instrumented __asan_mem*()
> > +# instead. With compilers that don't support this option, compiler-inserted
> > +# memintrinsics won't be checked by KASAN on GENERIC_ENTRY architectures.
> > +CFLAGS_KASAN += $(call cc-param,asan-kernel-mem-intrinsic-prefix=1)
> > +
> > endif # CONFIG_KASAN_GENERIC
> >
> > ifdef CONFIG_KASAN_SW_TAGS
> > @@ -54,6 +59,9 @@ CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
> > $(call cc-param,hwasan-inline-all-checks=0) \
> > $(instrumentation_flags)
> >
> > +# Instrument memcpy/memset/memmove calls by using instrumented __hwasan_mem*().
> > +CFLAGS_KASAN += $(call cc-param,hwasan-kernel-mem-intrinsic-prefix=1)
>
> This patch breaks the arm64 kernel builds with KASAN_SW_TAGS enabled and
> clang prior to version 15. Those prior clang versions don't like the
> '-mllvm -hwasan-kernel-mem-intrinsic-prefix=1' option, end up printing
> the help text instead of generating the object.
>
> Do we need some combination of cc-option and cc-param? Or at least
> disable this instrumentation if earlier clang versions are used.
>
> It's already in mainline as commit
> 51287dcb00cc715c27bf6a6b4dbd431621c5b65a.
Arnd posted a patch, but the reason why a workaround is needed is
quite unfortunate:
https://lore.kernel.org/all/CANpmjNMwYosrvqh4ogDO8rgn+SeDHM2b-shD21wTypm_6MMe=g@mail.gmail.com/
Clang apparently interprets unknown options that start with "-h..",
i.e. "-mllvm -h..." as a request to print help text, which has exit
code 0. So this is only a problem for hwasan options.