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Date:   Tue, 20 Sep 2022 12:22:01 -0700
From:   Kees Cook <keescook@...omium.org>
To:     linux-hardening@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, llvm@...ts.linux.dev,
        Siddhesh Poyarekar <siddhesh@...plt.org>,
        Arnd Bergmann <arnd@...db.de>, Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Miguel Ojeda <ojeda@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH 3/4] fortify: Convert to struct vs member helpers

In preparation for adding support for __builtin_dynamic_object_size(),
wrap each instance of __builtin_object_size(p, N) with either the new
__struct_size(p) as __bos(p, 0), or __member_size(p) as __bos(p, 1).
This will allow us to replace the definitions with __bdos() next.
There are no binary differences from this change.

Cc: Nathan Chancellor <nathan@...nel.org>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Tom Rix <trix@...hat.com>
Cc: linux-hardening@...r.kernel.org
Cc: llvm@...ts.linux.dev
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/linux/fortify-string.h | 68 +++++++++++++++++-----------------
 1 file changed, 35 insertions(+), 33 deletions(-)

diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
index 71c0a432c638..3f1178584d7b 100644
--- a/include/linux/fortify-string.h
+++ b/include/linux/fortify-string.h
@@ -20,7 +20,7 @@ void __write_overflow_field(size_t avail, size_t wanted) __compiletime_warning("
 ({								\
 	unsigned char *__p = (unsigned char *)(p);		\
 	size_t __ret = SIZE_MAX;				\
-	size_t __p_size = __builtin_object_size(p, 1);		\
+	size_t __p_size = __member_size(p);			\
 	if (__p_size != SIZE_MAX &&				\
 	    __builtin_constant_p(*__p)) {			\
 		size_t __p_len = __p_size - 1;			\
@@ -72,13 +72,15 @@ extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size)
 	__underlying_memcpy(dst, src, bytes)
 
 /*
- * Clang's use of __builtin_object_size() within inlines needs hinting via
- * __pass_object_size(). The preference is to only ever use type 1 (member
+ * Clang's use of __builtin_*object_size() within inlines needs hinting via
+ * __pass_*object_size(). The preference is to only ever use type 1 (member
  * size, rather than struct size), but there remain some stragglers using
  * type 0 that will be converted in the future.
  */
-#define POS	__pass_object_size(1)
-#define POS0	__pass_object_size(0)
+#define POS			__pass_object_size(1)
+#define POS0			__pass_object_size(0)
+#define __struct_size(p)	__builtin_object_size(p, 0)
+#define __member_size(p)	__builtin_object_size(p, 1)
 
 #define __compiletime_lessthan(bounds, length)	(	\
 	__builtin_constant_p(length) &&			\
@@ -121,7 +123,7 @@ extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size)
 __FORTIFY_INLINE __diagnose_as(__builtin_strncpy, 1, 2, 3)
 char *strncpy(char * const POS p, const char *q, __kernel_size_t size)
 {
-	size_t p_size = __builtin_object_size(p, 1);
+	size_t p_size = __member_size(p);
 
 	if (__compiletime_lessthan(p_size, size))
 		__write_overflow();
@@ -133,7 +135,7 @@ char *strncpy(char * const POS p, const char *q, __kernel_size_t size)
 __FORTIFY_INLINE __diagnose_as(__builtin_strcat, 1, 2)
 char *strcat(char * const POS p, const char *q)
 {
-	size_t p_size = __builtin_object_size(p, 1);
+	size_t p_size = __member_size(p);
 
 	if (p_size == SIZE_MAX)
 		return __underlying_strcat(p, q);
@@ -145,7 +147,7 @@ char *strcat(char * const POS p, const char *q)
 extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(strnlen);
 __FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size_t maxlen)
 {
-	size_t p_size = __builtin_object_size(p, 1);
+	size_t p_size = __member_size(p);
 	size_t p_len = __compiletime_strlen(p);
 	size_t ret;
 
@@ -175,7 +177,7 @@ __FORTIFY_INLINE __diagnose_as(__builtin_strlen, 1)
 __kernel_size_t __fortify_strlen(const char * const POS p)
 {
 	__kernel_size_t ret;
-	size_t p_size = __builtin_object_size(p, 1);
+	size_t p_size = __member_size(p);
 
 	/* Give up if we don't know how large p is. */
 	if (p_size == SIZE_MAX)
@@ -190,8 +192,8 @@ __kernel_size_t __fortify_strlen(const char * const POS p)
 extern size_t __real_strlcpy(char *, const char *, size_t) __RENAME(strlcpy);
 __FORTIFY_INLINE size_t strlcpy(char * const POS p, const char * const POS q, size_t size)
 {
-	size_t p_size = __builtin_object_size(p, 1);
-	size_t q_size = __builtin_object_size(q, 1);
+	size_t p_size = __member_size(p);
+	size_t q_size = __member_size(q);
 	size_t q_len;	/* Full count of source string length. */
 	size_t len;	/* Count of characters going into destination. */
 
@@ -219,8 +221,8 @@ __FORTIFY_INLINE ssize_t strscpy(char * const POS p, const char * const POS q, s
 {
 	size_t len;
 	/* Use string size rather than possible enclosing struct size. */
-	size_t p_size = __builtin_object_size(p, 1);
-	size_t q_size = __builtin_object_size(q, 1);
+	size_t p_size = __member_size(p);
+	size_t q_size = __member_size(q);
 
 	/* If we cannot get size of p and q default to call strscpy. */
 	if (p_size == SIZE_MAX && q_size == SIZE_MAX)
@@ -265,8 +267,8 @@ __FORTIFY_INLINE __diagnose_as(__builtin_strncat, 1, 2, 3)
 char *strncat(char * const POS p, const char * const POS q, __kernel_size_t count)
 {
 	size_t p_len, copy_len;
-	size_t p_size = __builtin_object_size(p, 1);
-	size_t q_size = __builtin_object_size(q, 1);
+	size_t p_size = __member_size(p);
+	size_t q_size = __member_size(q);
 
 	if (p_size == SIZE_MAX && q_size == SIZE_MAX)
 		return __underlying_strncat(p, q, count);
@@ -324,11 +326,11 @@ __FORTIFY_INLINE void fortify_memset_chk(__kernel_size_t size,
 })
 
 /*
- * __builtin_object_size() must be captured here to avoid evaluating argument
- * side-effects further into the macro layers.
+ * __struct_size() vs __member_size() must be captured here to avoid
+ * evaluating argument side-effects further into the macro layers.
  */
 #define memset(p, c, s) __fortify_memset_chk(p, c, s,			\
-		__builtin_object_size(p, 0), __builtin_object_size(p, 1))
+		__struct_size(p), __member_size(p))
 
 /*
  * To make sure the compiler can enforce protection against buffer overflows,
@@ -421,7 +423,7 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size,
 	 * fake flexible arrays, until they are all converted to
 	 * proper flexible arrays.
 	 *
-	 * The implementation of __builtin_object_size() behaves
+	 * The implementation of __builtin_*object_size() behaves
 	 * like sizeof() when not directly referencing a flexible
 	 * array member, which means there will be many bounds checks
 	 * that will appear at run-time, without a way for them to be
@@ -487,22 +489,22 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size,
  */
 
 /*
- * __builtin_object_size() must be captured here to avoid evaluating argument
- * side-effects further into the macro layers.
+ * __struct_size() vs __member_size() must be captured here to avoid
+ * evaluating argument side-effects further into the macro layers.
  */
 #define memcpy(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), \
+		__struct_size(p), __struct_size(q),			\
+		__member_size(p), __member_size(q),			\
 		memcpy)
 #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), \
+		__struct_size(p), __struct_size(q),			\
+		__member_size(p), __member_size(q),			\
 		memmove)
 
 extern void *__real_memscan(void *, int, __kernel_size_t) __RENAME(memscan);
 __FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size)
 {
-	size_t p_size = __builtin_object_size(p, 0);
+	size_t p_size = __struct_size(p);
 
 	if (__compiletime_lessthan(p_size, size))
 		__read_overflow();
@@ -514,8 +516,8 @@ __FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size)
 __FORTIFY_INLINE __diagnose_as(__builtin_memcmp, 1, 2, 3)
 int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t size)
 {
-	size_t p_size = __builtin_object_size(p, 0);
-	size_t q_size = __builtin_object_size(q, 0);
+	size_t p_size = __struct_size(p);
+	size_t q_size = __struct_size(q);
 
 	if (__builtin_constant_p(size)) {
 		if (__compiletime_lessthan(p_size, size))
@@ -531,7 +533,7 @@ int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t
 __FORTIFY_INLINE __diagnose_as(__builtin_memchr, 1, 2, 3)
 void *memchr(const void * const POS0 p, int c, __kernel_size_t size)
 {
-	size_t p_size = __builtin_object_size(p, 0);
+	size_t p_size = __struct_size(p);
 
 	if (__compiletime_lessthan(p_size, size))
 		__read_overflow();
@@ -543,7 +545,7 @@ void *memchr(const void * const POS0 p, int c, __kernel_size_t size)
 void *__real_memchr_inv(const void *s, int c, size_t n) __RENAME(memchr_inv);
 __FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size)
 {
-	size_t p_size = __builtin_object_size(p, 0);
+	size_t p_size = __struct_size(p);
 
 	if (__compiletime_lessthan(p_size, size))
 		__read_overflow();
@@ -555,7 +557,7 @@ __FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size)
 extern void *__real_kmemdup(const void *src, size_t len, gfp_t gfp) __RENAME(kmemdup);
 __FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp)
 {
-	size_t p_size = __builtin_object_size(p, 0);
+	size_t p_size = __struct_size(p);
 
 	if (__compiletime_lessthan(p_size, size))
 		__read_overflow();
@@ -568,8 +570,8 @@ __FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp
 __FORTIFY_INLINE __diagnose_as(__builtin_strcpy, 1, 2)
 char *strcpy(char * const POS p, const char * const POS q)
 {
-	size_t p_size = __builtin_object_size(p, 1);
-	size_t q_size = __builtin_object_size(q, 1);
+	size_t p_size = __member_size(p);
+	size_t q_size = __member_size(q);
 	size_t size;
 
 	/* If neither buffer size is known, immediately give up. */
-- 
2.34.1

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