Commit 9f7d69c5 authored by Kees Cook's avatar Kees Cook
Browse files

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@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Tom Rix <trix@redhat.com>
Cc: linux-hardening@vger.kernel.org
Cc: llvm@lists.linux.dev
Link: https://lore.kernel.org/lkml/20220920192202.190793-4-keescook@chromium.org


Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent fa35198f

include/linux/fortify-string.h

+35 −33
Original line number Diff line number Diff line
@@ -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 __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((bounds) < (length)) &&	\
@@ -120,7 +122,7 @@ 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();
@@ -132,7 +134,7 @@ 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);
@@ -144,7 +146,7 @@ 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;
@@ -174,7 +176,7 @@ __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)
@@ -189,8 +191,8 @@ __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. */
@@ -218,8 +220,8 @@ __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)
@@ -264,8 +266,8 @@ __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);
@@ -323,11 +325,11 @@ __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,
@@ -420,7 +422,7 @@ __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
@@ -486,22 +488,22 @@ __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();
@@ -513,8 +515,8 @@ __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))
@@ -530,7 +532,7 @@ 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();
@@ -542,7 +544,7 @@ 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();
@@ -554,7 +556,7 @@ __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();
@@ -567,8 +569,8 @@ __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. */