libio: Improve fortify with clang

It improve fortify checks for sprintf, vsprintf, vsnsprintf, fprintf,
dprintf, asprintf, __asprintf, obstack_printf, gets, fgets,
fgets_unlocked, fread, and fread_unlocked.  The runtime checks have
similar support coverage as with GCC.

For function with variadic argument (sprintf, snprintf, fprintf, printf,
dprintf, asprintf, __asprintf, obstack_printf) the fortify wrapper calls
the va_arg version since clang does not support __va_arg_pack.

Checked on aarch64, armhf, x86_64, and i686.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

libio/bits/stdio2.h

@@ -31,15 +31,29 @@ __NTH (sprintf (char *__restrict __s, const char *__restrict __fmt, ...))
 				  __glibc_objsize (__s), __fmt,
 				  __va_arg_pack ());
 }
+#elif __fortify_use_clang
+/* clang does not have __va_arg_pack, so defer to va_arg version.  */
+__fortify_function_error_function __attribute_overloadable__ int
+__NTH (sprintf (__fortify_clang_overload_arg (char *, __restrict, __s),
+		const char *__restrict __fmt, ...))
+{
+  __gnuc_va_list __fortify_ap;
+  __builtin_va_start (__fortify_ap, __fmt);
+  int __r = __builtin___vsprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
+				      __glibc_objsize (__s), __fmt,
+				      __fortify_ap);
+  __builtin_va_end (__fortify_ap);
+  return __r;
+}
 #elif !defined __cplusplus
 # define sprintf(str, ...) \
   __builtin___sprintf_chk (str, __USE_FORTIFY_LEVEL - 1,		      \
 			   __glibc_objsize (str), __VA_ARGS__)
 #endif
 
-__fortify_function int
+__fortify_function __attribute_overloadable__ int
-__NTH (vsprintf (char *__restrict __s, const char *__restrict __fmt,
+__NTH (vsprintf (__fortify_clang_overload_arg (char *, __restrict, __s),
-		 __gnuc_va_list __ap))
+		 const char *__restrict __fmt, __gnuc_va_list __ap))
 {
   return __builtin___vsprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
 				   __glibc_objsize (__s), __fmt, __ap);
@@ -55,15 +69,33 @@ __NTH (snprintf (char *__restrict __s, size_t __n,
 				   __glibc_objsize (__s), __fmt,
 				   __va_arg_pack ());
 }
+# elif __fortify_use_clang
+/* clang does not have __va_arg_pack, so defer to va_arg version.  */
+__fortify_function_error_function __attribute_overloadable__ int
+__NTH (snprintf (__fortify_clang_overload_arg (char *, __restrict, __s),
+		 size_t __n, const char *__restrict __fmt, ...))
+{
+  __gnuc_va_list __fortify_ap;
+  __builtin_va_start (__fortify_ap, __fmt);
+  int __r = __builtin___vsnprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
+				       __glibc_objsize (__s), __fmt,
+				       __fortify_ap);
+  __builtin_va_end (__fortify_ap);
+  return __r;
+}
 # elif !defined __cplusplus
 #  define snprintf(str, len, ...) \
   __builtin___snprintf_chk (str, len, __USE_FORTIFY_LEVEL - 1,		      \
 			    __glibc_objsize (str), __VA_ARGS__)
 # endif
 
-__fortify_function int
+__fortify_function __attribute_overloadable__ int
-__NTH (vsnprintf (char *__restrict __s, size_t __n,
+__NTH (vsnprintf (__fortify_clang_overload_arg (char *, __restrict, __s),
-		  const char *__restrict __fmt, __gnuc_va_list __ap))
+		  size_t __n, const char *__restrict __fmt,
+		  __gnuc_va_list __ap))
+     __fortify_clang_warning (__fortify_clang_bos_static_lt (__n, __s),
+			      "call to vsnprintf may overflow the destination "
+			      "buffer")
 {
   return __builtin___vsnprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
 				    __glibc_objsize (__s), __fmt, __ap);
@@ -85,6 +117,30 @@ printf (const char *__restrict __fmt, ...)
 {
   return __printf_chk (__USE_FORTIFY_LEVEL - 1, __fmt, __va_arg_pack ());
 }
+# elif __fortify_use_clang
+/* clang does not have __va_arg_pack, so defer to va_arg version.  */
+__fortify_function_error_function __attribute_overloadable__ __nonnull ((1)) int
+fprintf (__fortify_clang_overload_arg (FILE *, __restrict, __stream),
+	 const char *__restrict __fmt, ...)
+{
+  __gnuc_va_list __fortify_ap;
+  __builtin_va_start (__fortify_ap, __fmt);
+  int __r = __builtin___vfprintf_chk (__stream, __USE_FORTIFY_LEVEL - 1,
+				      __fmt, __fortify_ap);
+  __builtin_va_end (__fortify_ap);
+  return __r;
+}
+
+__fortify_function_error_function __attribute_overloadable__ int
+printf (__fortify_clang_overload_arg (const char *, __restrict, __fmt), ...)
+{
+  __gnuc_va_list __fortify_ap;
+  __builtin_va_start (__fortify_ap, __fmt);
+  int __r = __builtin___vprintf_chk (__USE_FORTIFY_LEVEL - 1, __fmt,
+				     __fortify_ap);
+  __builtin_va_end (__fortify_ap);
+  return __r;
+}
 # elif !defined __cplusplus
 #  define printf(...) \
   __printf_chk (__USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
@@ -92,8 +148,9 @@ printf (const char *__restrict __fmt, ...)
   __fprintf_chk (stream, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
 # endif
 
-__fortify_function int
+__fortify_function __attribute_overloadable__ int
-vprintf (const char *__restrict __fmt, __gnuc_va_list __ap)
+vprintf (__fortify_clang_overload_arg (const char *, __restrict, __fmt),
+	 __gnuc_va_list __ap)
 {
 #ifdef __USE_EXTERN_INLINES
   return __vfprintf_chk (stdout, __USE_FORTIFY_LEVEL - 1, __fmt, __ap);
@@ -117,6 +174,18 @@ dprintf (int __fd, const char *__restrict __fmt, ...)
   return __dprintf_chk (__fd, __USE_FORTIFY_LEVEL - 1, __fmt,
 			__va_arg_pack ());
 }
+#  elif __fortify_use_clang
+__fortify_function_error_function __attribute_overloadable__ int
+dprintf (int __fd, __fortify_clang_overload_arg (const char *, __restrict,
+						 __fmt), ...)
+{
+  __gnuc_va_list __fortify_ap;
+  __builtin_va_start (__fortify_ap, __fmt);
+  int __r = __vdprintf_chk (__fd, __USE_FORTIFY_LEVEL - 1, __fmt,
+			    __fortify_ap);
+  __builtin_va_end (__fortify_ap);
+  return __r;
+}
 #  elif !defined __cplusplus
 #   define dprintf(fd, ...) \
   __dprintf_chk (fd, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
@@ -153,6 +222,43 @@ __NTH (obstack_printf (struct obstack *__restrict __obstack,
   return __obstack_printf_chk (__obstack, __USE_FORTIFY_LEVEL - 1, __fmt,
 			       __va_arg_pack ());
 }
+#  elif __fortify_use_clang
+__fortify_function_error_function __attribute_overloadable__ int
+__NTH (asprintf (__fortify_clang_overload_arg (char **, __restrict, __ptr),
+		 const char *__restrict __fmt, ...))
+{
+  __gnuc_va_list __fortify_ap;
+  __builtin_va_start (__fortify_ap, __fmt);
+  int __r = __vasprintf_chk (__ptr, __USE_FORTIFY_LEVEL - 1, __fmt,
+			     __fortify_ap);
+  __builtin_va_end (__fortify_ap);
+  return __r;
+}
+
+__fortify_function_error_function __attribute_overloadable__ int
+__NTH (__asprintf (__fortify_clang_overload_arg (char **, __restrict, __ptr),
+		   const char *__restrict __fmt, ...))
+{
+  __gnuc_va_list __fortify_ap;
+  __builtin_va_start (__fortify_ap, __fmt);
+  int __r = __vasprintf_chk (__ptr, __USE_FORTIFY_LEVEL - 1, __fmt,
+			     __fortify_ap);
+  __builtin_va_end (__fortify_ap);
+  return __r;
+}
+
+__fortify_function_error_function __attribute_overloadable__ int
+__NTH (obstack_printf (__fortify_clang_overload_arg (struct obstack *,
+						     __restrict, __obstack),
+		       const char *__restrict __fmt, ...))
+{
+  __gnuc_va_list __fortify_ap;
+  __builtin_va_start (__fortify_ap, __fmt);
+  int __r = __obstack_vprintf_chk (__obstack, __USE_FORTIFY_LEVEL - 1,
+				   __fmt, __fortify_ap);
+  __builtin_va_end (__fortify_ap);
+  return __r;
+}
 #  elif !defined __cplusplus
 #   define asprintf(ptr, ...) \
   __asprintf_chk (ptr, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
@@ -182,8 +288,11 @@ __NTH (obstack_vprintf (struct obstack *__restrict __obstack,
 #endif
 
 #if __GLIBC_USE (DEPRECATED_GETS)
-__fortify_function __wur char *
+__fortify_function __wur __attribute_overloadable__ char *
-gets (char *__str)
+gets (__fortify_clang_overload_arg (char *, , __str))
+     __fortify_clang_warning (__glibc_objsize (__str) == (size_t) -1,
+			      "please use fgets or getline instead, gets "
+			      "can not specify buffer size")
 {
   if (__glibc_objsize (__str) != (size_t) -1)
     return __gets_chk (__str, __glibc_objsize (__str));
@@ -192,48 +301,70 @@ gets (char *__str)
 #endif
 
 __fortify_function __wur __fortified_attr_access (__write_only__, 1, 2)
-__nonnull ((3)) char *
+__nonnull ((3)) __attribute_overloadable__ char *
-fgets (char *__restrict __s, int __n, FILE *__restrict __stream)
+fgets (__fortify_clang_overload_arg (char *, __restrict, __s), int __n,
+       FILE *__restrict __stream)
+     __fortify_clang_warning (__fortify_clang_bos_static_lt (__n, __s) && __n > 0,
+			      "fgets called with bigger size than length of "
+			      "destination buffer")
 {
   size_t sz = __glibc_objsize (__s);
   if (__glibc_safe_or_unknown_len (__n, sizeof (char), sz))
     return __fgets_alias (__s, __n, __stream);
+#if !__fortify_use_clang
   if (__glibc_unsafe_len (__n, sizeof (char), sz))
     return __fgets_chk_warn (__s, sz, __n, __stream);
+#endif
   return __fgets_chk (__s, sz, __n, __stream);
 }
 
-__fortify_function __wur __nonnull ((4)) size_t
+__fortify_function __wur __nonnull ((4)) __attribute_overloadable__ size_t
-fread (void *__restrict __ptr, size_t __size, size_t __n,
+fread (__fortify_clang_overload_arg (void *, __restrict, __ptr),
-       FILE *__restrict __stream)
+       size_t __size, size_t __n, FILE *__restrict __stream)
+     __fortify_clang_warning (__fortify_clang_bos0_static_lt (__size * __n, __ptr)
+			      && !__fortify_clang_mul_may_overflow (__size, __n),
+			      "fread called with bigger size * n than length "
+			      "of destination buffer")
 {
   size_t sz = __glibc_objsize0 (__ptr);
   if (__glibc_safe_or_unknown_len (__n, __size, sz))
     return __fread_alias (__ptr, __size, __n, __stream);
+#if !__fortify_use_clang
   if (__glibc_unsafe_len (__n, __size, sz))
     return __fread_chk_warn (__ptr, sz, __size, __n, __stream);
+#endif
   return __fread_chk (__ptr, sz, __size, __n, __stream);
 }
 
 #ifdef __USE_GNU
 __fortify_function __wur __fortified_attr_access (__write_only__, 1, 2)
-__nonnull ((3)) char *
+__nonnull ((3)) __attribute_overloadable__ char *
-fgets_unlocked (char *__restrict __s, int __n, FILE *__restrict __stream)
+fgets_unlocked (__fortify_clang_overload_arg (char *, __restrict, __s),
+		int __n, FILE *__restrict __stream)
+     __fortify_clang_warning (__fortify_clang_bos_static_lt (__n, __s) && __n > 0,
+			      "fgets called with bigger size than length of "
+			      "destination buffer")
 {
   size_t sz = __glibc_objsize (__s);
   if (__glibc_safe_or_unknown_len (__n, sizeof (char), sz))
     return __fgets_unlocked_alias (__s, __n, __stream);
+#if !__fortify_use_clang
   if (__glibc_unsafe_len (__n, sizeof (char), sz))
     return __fgets_unlocked_chk_warn (__s, sz, __n, __stream);
+#endif
   return __fgets_unlocked_chk (__s, sz, __n, __stream);
 }
 #endif
 
 #ifdef __USE_MISC
 # undef fread_unlocked
-__fortify_function __wur __nonnull ((4)) size_t
+__fortify_function __wur __nonnull ((4)) __attribute_overloadable__ size_t
-fread_unlocked (void *__restrict __ptr, size_t __size, size_t __n,
+fread_unlocked (__fortify_clang_overload_arg0 (void *, __restrict, __ptr),
-		FILE *__restrict __stream)
+		size_t __size, size_t __n, FILE *__restrict __stream)
+     __fortify_clang_warning (__fortify_clang_bos0_static_lt (__size * __n, __ptr)
+			      && !__fortify_clang_mul_may_overflow (__size, __n),
+			      "fread_unlocked called with bigger size * n than "
+			      "length of destination buffer")
 {
   size_t sz = __glibc_objsize0 (__ptr);
   if (__glibc_safe_or_unknown_len (__n, __size, sz))
@@ -261,8 +392,10 @@ fread_unlocked (void *__restrict __ptr, size_t __size, size_t __n,
 # endif
       return __fread_unlocked_alias (__ptr, __size, __n, __stream);
     }
+# if !__fortify_use_clang
   if (__glibc_unsafe_len (__n, __size, sz))
     return __fread_unlocked_chk_warn (__ptr, sz, __size, __n, __stream);
+# endif
   return __fread_unlocked_chk (__ptr, sz, __size, __n, __stream);
 
 }