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e938c02748402c50f60ba0eb983273e7b52937d1
glibc/libio/bits/stdio2.h
Siddhesh Poyarekar e938c02748 Don't add access size hints to fortifiable functions 
In the context of a function definition, the size hints imply that the
size of an object pointed to by one parameter is another parameter.
This doesn't make sense for the fortified versions of the functions
since that's the bit it's trying to validate.

This is harmless with __builtin_object_size since it has fairly simple
semantics when it comes to objects passed as function parameters.
With __builtin_dynamic_object_size we could (as my patchset for gcc[1]
already does) use the access attribute to determine the object size in
the general case but it misleads the fortified functions.

Basically the problem occurs when access attributes are present on
regular functions that have inline fortified definitions to generate
_chk variants; the attributes get inherited by these definitions,
causing problems when analyzing them.  For example with poll(fds, nfds,
timeout), nfds is hinted using the __attr_access as being the size of
fds.

Now, when analyzing the inline function definition in bits/poll2.h, the
compiler sees that nfds is the size of fds and tries to use that
information in the function body.  In _FORTIFY_SOURCE=3 case, where the
object size could be a non-constant expression, this information results
in the conclusion that nfds is the size of fds, which defeats the
purpose of the implementation because we're trying to check here if nfds
does indeed represent the size of fds.  Hence for this case, it is best
to not have the access attribute.

With the attributes gone, the expression evaluation should get delayed
until the function is actually inlined into its destinations.

Disable the access attribute for fortified function inline functions
when building at _FORTIFY_SOURCE=3 to make this work better.  The
access attributes remain for the _chk variants since they can be used
by the compiler to warn when the caller is passing invalid arguments.

[1] https://gcc.gnu.org/pipermail/gcc-patches/2021-October/581125.html

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
2021-10-20 08:33:31 +05:30

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/* Checking macros for stdio functions.
Copyright (C) 2004-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#ifndef _BITS_STDIO2_H
#define _BITS_STDIO2_H 1
#ifndef _STDIO_H
# error "Never include <bits/stdio2.h> directly; use <stdio.h> instead."
#endif
extern int __sprintf_chk (char *__restrict __s, int __flag, size_t __slen,
const char *__restrict __format, ...) __THROW
__attr_access ((__write_only__, 1, 3));
extern int __vsprintf_chk (char *__restrict __s, int __flag, size_t __slen,
const char *__restrict __format,
__gnuc_va_list __ap) __THROW
__attr_access ((__write_only__, 1, 3));
#ifdef __va_arg_pack
__fortify_function int
__NTH (sprintf (char *__restrict __s, const char *__restrict __fmt, ...))
{
return __builtin___sprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
__glibc_objsize (__s), __fmt,
__va_arg_pack ());
}
#elif !defined __cplusplus
# define sprintf(str, ...) \
__builtin___sprintf_chk (str, __USE_FORTIFY_LEVEL - 1, \
__glibc_objsize (str), __VA_ARGS__)
#endif
__fortify_function int
__NTH (vsprintf (char *__restrict __s, const char *__restrict __fmt,
__gnuc_va_list __ap))
{
return __builtin___vsprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
__glibc_objsize (__s), __fmt, __ap);
}
#if defined __USE_ISOC99 || defined __USE_UNIX98
extern int __snprintf_chk (char *__restrict __s, size_t __n, int __flag,
size_t __slen, const char *__restrict __format,
...) __THROW
__attr_access ((__write_only__, 1, 2));
extern int __vsnprintf_chk (char *__restrict __s, size_t __n, int __flag,
size_t __slen, const char *__restrict __format,
__gnuc_va_list __ap) __THROW;
# ifdef __va_arg_pack
__fortify_function int
__NTH (snprintf (char *__restrict __s, size_t __n,
const char *__restrict __fmt, ...))
{
return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
__glibc_objsize (__s), __fmt,
__va_arg_pack ());
}
# 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
__NTH (vsnprintf (char *__restrict __s, size_t __n,
const char *__restrict __fmt, __gnuc_va_list __ap))
{
return __builtin___vsnprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
__glibc_objsize (__s), __fmt, __ap);
}
#endif
#if __USE_FORTIFY_LEVEL > 1
extern int __fprintf_chk (FILE *__restrict __stream, int __flag,
const char *__restrict __format, ...);
extern int __printf_chk (int __flag, const char *__restrict __format, ...);
extern int __vfprintf_chk (FILE *__restrict __stream, int __flag,
const char *__restrict __format, __gnuc_va_list __ap);
extern int __vprintf_chk (int __flag, const char *__restrict __format,
__gnuc_va_list __ap);
# ifdef __va_arg_pack
__fortify_function int
fprintf (FILE *__restrict __stream, const char *__restrict __fmt, ...)
{
return __fprintf_chk (__stream, __USE_FORTIFY_LEVEL - 1, __fmt,
__va_arg_pack ());
}
__fortify_function int
printf (const char *__restrict __fmt, ...)
{
return __printf_chk (__USE_FORTIFY_LEVEL - 1, __fmt, __va_arg_pack ());
}
# elif !defined __cplusplus
# define printf(...) \
__printf_chk (__USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
# define fprintf(stream, ...) \
__fprintf_chk (stream, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
# endif
__fortify_function int
vprintf (const char *__restrict __fmt, __gnuc_va_list __ap)
{
#ifdef __USE_EXTERN_INLINES
return __vfprintf_chk (stdout, __USE_FORTIFY_LEVEL - 1, __fmt, __ap);
#else
return __vprintf_chk (__USE_FORTIFY_LEVEL - 1, __fmt, __ap);
#endif
}
__fortify_function int
vfprintf (FILE *__restrict __stream,
const char *__restrict __fmt, __gnuc_va_list __ap)
{
return __vfprintf_chk (__stream, __USE_FORTIFY_LEVEL - 1, __fmt, __ap);
}
# ifdef __USE_XOPEN2K8
extern int __dprintf_chk (int __fd, int __flag, const char *__restrict __fmt,
...) __attribute__ ((__format__ (__printf__, 3, 4)));
extern int __vdprintf_chk (int __fd, int __flag,
const char *__restrict __fmt, __gnuc_va_list __arg)
__attribute__ ((__format__ (__printf__, 3, 0)));
# ifdef __va_arg_pack
__fortify_function int
dprintf (int __fd, const char *__restrict __fmt, ...)
{
return __dprintf_chk (__fd, __USE_FORTIFY_LEVEL - 1, __fmt,
__va_arg_pack ());
}
# elif !defined __cplusplus
# define dprintf(fd, ...) \
__dprintf_chk (fd, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
# endif
__fortify_function int
vdprintf (int __fd, const char *__restrict __fmt, __gnuc_va_list __ap)
{
return __vdprintf_chk (__fd, __USE_FORTIFY_LEVEL - 1, __fmt, __ap);
}
# endif
# ifdef __USE_GNU
extern int __asprintf_chk (char **__restrict __ptr, int __flag,
const char *__restrict __fmt, ...)
__THROW __attribute__ ((__format__ (__printf__, 3, 4))) __wur;
extern int __vasprintf_chk (char **__restrict __ptr, int __flag,
const char *__restrict __fmt, __gnuc_va_list __arg)
__THROW __attribute__ ((__format__ (__printf__, 3, 0))) __wur;
extern int __obstack_printf_chk (struct obstack *__restrict __obstack,
int __flag, const char *__restrict __format,
...)
__THROW __attribute__ ((__format__ (__printf__, 3, 4)));
extern int __obstack_vprintf_chk (struct obstack *__restrict __obstack,
int __flag,
const char *__restrict __format,
__gnuc_va_list __args)
__THROW __attribute__ ((__format__ (__printf__, 3, 0)));
# ifdef __va_arg_pack
__fortify_function int
__NTH (asprintf (char **__restrict __ptr, const char *__restrict __fmt, ...))
{
return __asprintf_chk (__ptr, __USE_FORTIFY_LEVEL - 1, __fmt,
__va_arg_pack ());
}
__fortify_function int
__NTH (__asprintf (char **__restrict __ptr, const char *__restrict __fmt,
...))
{
return __asprintf_chk (__ptr, __USE_FORTIFY_LEVEL - 1, __fmt,
__va_arg_pack ());
}
__fortify_function int
__NTH (obstack_printf (struct obstack *__restrict __obstack,
const char *__restrict __fmt, ...))
{
return __obstack_printf_chk (__obstack, __USE_FORTIFY_LEVEL - 1, __fmt,
__va_arg_pack ());
}
# elif !defined __cplusplus
# define asprintf(ptr, ...) \
__asprintf_chk (ptr, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
# define __asprintf(ptr, ...) \
__asprintf_chk (ptr, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
# define obstack_printf(obstack, ...) \
__obstack_printf_chk (obstack, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
# endif
__fortify_function int
__NTH (vasprintf (char **__restrict __ptr, const char *__restrict __fmt,
__gnuc_va_list __ap))
{
return __vasprintf_chk (__ptr, __USE_FORTIFY_LEVEL - 1, __fmt, __ap);
}
__fortify_function int
__NTH (obstack_vprintf (struct obstack *__restrict __obstack,
const char *__restrict __fmt, __gnuc_va_list __ap))
{
return __obstack_vprintf_chk (__obstack, __USE_FORTIFY_LEVEL - 1, __fmt,
__ap);
}
# endif
#endif
#if __GLIBC_USE (DEPRECATED_GETS)
extern char *__gets_chk (char *__str, size_t) __wur;
extern char *__REDIRECT (__gets_warn, (char *__str), gets)
__wur __warnattr ("please use fgets or getline instead, gets can't "
"specify buffer size");
__fortify_function __wur char *
gets (char *__str)
{
if (__glibc_objsize (__str) != (size_t) -1)
return __gets_chk (__str, __glibc_objsize (__str));
return __gets_warn (__str);
}
#endif
extern char *__fgets_chk (char *__restrict __s, size_t __size, int __n,
FILE *__restrict __stream)
__wur __attr_access ((__write_only__, 1, 3));
extern char *__REDIRECT (__fgets_alias,
(char *__restrict __s, int __n,
FILE *__restrict __stream), fgets)
__wur __attr_access ((__write_only__, 1, 2));
extern char *__REDIRECT (__fgets_chk_warn,
(char *__restrict __s, size_t __size, int __n,
FILE *__restrict __stream), __fgets_chk)
__wur __warnattr ("fgets called with bigger size than length "
"of destination buffer");
__fortify_function __wur __fortified_attr_access (__write_only__, 1, 2) char *
fgets (char *__restrict __s, int __n, FILE *__restrict __stream)
{
if (__glibc_objsize (__s) != (size_t) -1)
{
if (!__builtin_constant_p (__n) || __n <= 0)
return __fgets_chk (__s, __glibc_objsize (__s), __n, __stream);
if ((size_t) __n > __glibc_objsize (__s))
return __fgets_chk_warn (__s, __glibc_objsize (__s), __n, __stream);
}
return __fgets_alias (__s, __n, __stream);
}
extern size_t __fread_chk (void *__restrict __ptr, size_t __ptrlen,
size_t __size, size_t __n,
FILE *__restrict __stream) __wur;
extern size_t __REDIRECT (__fread_alias,
(void *__restrict __ptr, size_t __size,
size_t __n, FILE *__restrict __stream),
fread) __wur;
extern size_t __REDIRECT (__fread_chk_warn,
(void *__restrict __ptr, size_t __ptrlen,
size_t __size, size_t __n,
FILE *__restrict __stream),
__fread_chk)
__wur __warnattr ("fread called with bigger size * nmemb than length "
"of destination buffer");
__fortify_function __wur size_t
fread (void *__restrict __ptr, size_t __size, size_t __n,
FILE *__restrict __stream)
{
if (__glibc_objsize0 (__ptr) != (size_t) -1)
{
if (!__builtin_constant_p (__size)
|| !__builtin_constant_p (__n)
|| (__size | __n) >= (((size_t) 1) << (8 * sizeof (size_t) / 2)))
return __fread_chk (__ptr, __glibc_objsize0 (__ptr), __size, __n,
__stream);
if (__size * __n > __glibc_objsize0 (__ptr))
return __fread_chk_warn (__ptr, __glibc_objsize0 (__ptr), __size, __n,
__stream);
}
return __fread_alias (__ptr, __size, __n, __stream);
}
#ifdef __USE_GNU
extern char *__fgets_unlocked_chk (char *__restrict __s, size_t __size,
int __n, FILE *__restrict __stream)
__wur __attr_access ((__write_only__, 1, 3));
extern char *__REDIRECT (__fgets_unlocked_alias,
(char *__restrict __s, int __n,
FILE *__restrict __stream), fgets_unlocked)
__wur __attr_access ((__write_only__, 1, 2));
extern char *__REDIRECT (__fgets_unlocked_chk_warn,
(char *__restrict __s, size_t __size, int __n,
FILE *__restrict __stream), __fgets_unlocked_chk)
__wur __warnattr ("fgets_unlocked called with bigger size than length "
"of destination buffer");
__fortify_function __wur __fortified_attr_access (__write_only__, 1, 2) char *
fgets_unlocked (char *__restrict __s, int __n, FILE *__restrict __stream)
{
if (__glibc_objsize (__s) != (size_t) -1)
{
if (!__builtin_constant_p (__n) || __n <= 0)
return __fgets_unlocked_chk (__s, __glibc_objsize (__s), __n,
__stream);
if ((size_t) __n > __glibc_objsize (__s))
return __fgets_unlocked_chk_warn (__s, __glibc_objsize (__s), __n,
__stream);
}
return __fgets_unlocked_alias (__s, __n, __stream);
}
#endif
#ifdef __USE_MISC
# undef fread_unlocked
extern size_t __fread_unlocked_chk (void *__restrict __ptr, size_t __ptrlen,
size_t __size, size_t __n,
FILE *__restrict __stream) __wur;
extern size_t __REDIRECT (__fread_unlocked_alias,
(void *__restrict __ptr, size_t __size,
size_t __n, FILE *__restrict __stream),
fread_unlocked) __wur;
extern size_t __REDIRECT (__fread_unlocked_chk_warn,
(void *__restrict __ptr, size_t __ptrlen,
size_t __size, size_t __n,
FILE *__restrict __stream),
__fread_unlocked_chk)
__wur __warnattr ("fread_unlocked called with bigger size * nmemb than "
"length of destination buffer");
__fortify_function __wur size_t
fread_unlocked (void *__restrict __ptr, size_t __size, size_t __n,
FILE *__restrict __stream)
{
if (__glibc_objsize0 (__ptr) != (size_t) -1)
{
if (!__builtin_constant_p (__size)
|| !__builtin_constant_p (__n)
|| (__size | __n) >= (((size_t) 1) << (8 * sizeof (size_t) / 2)))
return __fread_unlocked_chk (__ptr, __glibc_objsize0 (__ptr), __size,
__n, __stream);
if (__size * __n > __glibc_objsize0 (__ptr))
return __fread_unlocked_chk_warn (__ptr, __glibc_objsize0 (__ptr),
__size, __n, __stream);
}
# ifdef __USE_EXTERN_INLINES
if (__builtin_constant_p (__size)
&& __builtin_constant_p (__n)
&& (__size | __n) < (((size_t) 1) << (8 * sizeof (size_t) / 2))
&& __size * __n <= 8)
{
size_t __cnt = __size * __n;
char *__cptr = (char *) __ptr;
if (__cnt == 0)
return 0;
for (; __cnt > 0; --__cnt)
{
int __c = getc_unlocked (__stream);
if (__c == EOF)
break;
*__cptr++ = __c;
}
return (__cptr - (char *) __ptr) / __size;
}
# endif
return __fread_unlocked_alias (__ptr, __size, __n, __stream);
}
#endif
#endif /* bits/stdio2.h. */
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