[PATCH 35/64] fortify: Detect struct member overflows in memmove() at compile-time

Kees Cook
2021-07-27T21:19:26Z

As done for memcpy(), also update memmove() to use the same tightened
compile-time checks under CONFIG_FORTIFY_SOURCE.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/x86/boot/compressed/misc.c | 3 ++-
arch/x86/lib/memcpy_32.c | 1 +
include/linux/fortify-string.h | 21 ++++---------------
.../read_overflow2_field-memmove.c | 5 +++++
.../write_overflow_field-memmove.c | 5 +++++
5 files changed, 17 insertions(+), 18 deletions(-)
create mode 100644 lib/test_fortify/read_overflow2_field-memmove.c
create mode 100644 lib/test_fortify/write_overflow_field-memmove.c

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 743f13ea25c1..83ff4354970e 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -34,10 +34,11 @@
* try to define their own functions if these are not defined as macros.
*/
#define memzero(s, n) memset((s), 0, (n))
+#ifndef memmove
#define memmove memmove
-
/* Functions used by the included decompressor code below. */
void *memmove(void *dest, const void *src, size_t n);
+#endif

/*
* This is set up by the setup-routine at boot-time
diff --git a/arch/x86/lib/memcpy_32.c b/arch/x86/lib/memcpy_32.c
index e565d1c9019e..f19b7fd07f04 100644
--- a/arch/x86/lib/memcpy_32.c
+++ b/arch/x86/lib/memcpy_32.c
@@ -4,6 +4,7 @@

#undef memcpy
#undef memset
+#undef memmove

__visible void *memcpy(void *to, const void *from, size_t n)
{
diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
index 5e79e626172b..2ffa5224aaac 100644
--- a/include/linux/fortify-string.h
+++ b/include/linux/fortify-string.h
@@ -284,22 +284,10 @@ __FORTIFY_INLINE void fortify_memcpy_chk(__kernel_size_t size,
__builtin_object_size(p, 0), __builtin_object_size(q, 0), \
__builtin_object_size(p, 1), __builtin_object_size(q, 1), \
memcpy)
-
-__FORTIFY_INLINE void *memmove(void *p, const void *q, __kernel_size_t size)
-{
- size_t p_size = __builtin_object_size(p, 0);
- size_t q_size = __builtin_object_size(q, 0);
-
- if (__builtin_constant_p(size)) {
- if (p_size < size)
- __write_overflow();
- if (q_size < size)
- __read_overflow2();
- }
- if (p_size < size || q_size < size)
- fortify_panic(__func__);
- return __underlying_memmove(p, q, size);
-}
+#define memmove(p, q, s) __fortify_memcpy_chk(p, q, s, \
+ __builtin_object_size(p, 0), __builtin_object_size(q, 0), \
+ __builtin_object_size(p, 1), __builtin_object_size(q, 1), \
+ memmove)

extern void *__real_memscan(void *, int, __kernel_size_t) __RENAME(memscan);
__FORTIFY_INLINE void *memscan(void *p, int c, __kernel_size_t size)
@@ -385,7 +373,6 @@ __FORTIFY_INLINE char *strcpy(char *p, const char *q)
/* Don't use these outside the FORITFY_SOURCE implementation */
#undef __underlying_memchr
#undef __underlying_memcmp
-#undef __underlying_memmove
#undef __underlying_memset
#undef __underlying_strcat
#undef __underlying_strcpy
diff --git a/lib/test_fortify/read_overflow2_field-memmove.c b/lib/test_fortify/read_overflow2_field-memmove.c
new file mode 100644
index 000000000000..6cc2724c8f62
--- /dev/null
+++ b/lib/test_fortify/read_overflow2_field-memmove.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ memmove(large, instance.buf, sizeof(instance.buf) + 1)
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/write_overflow_field-memmove.c b/lib/test_fortify/write_overflow_field-memmove.c
new file mode 100644
index 000000000000..377fcf9bb2fd
--- /dev/null
+++ b/lib/test_fortify/write_overflow_field-memmove.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ memmove(instance.buf, large, sizeof(instance.buf) + 1)
+
+#include "test_fortify.h"
--
2.30.2