fortify: Detect struct member overflows in memmove() at compile-time

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

@@ -37,10 +37,11 @@
  * 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

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)
 {

include/linux/fortify-string.h

@@ -309,22 +309,10 @@ __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)
@@ -413,7 +401,6 @@ __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

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"

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"