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Don't add access size hints to fortifiable functions

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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>
This commit is contained in:
Siddhesh Poyarekar 2021-10-12 12:29:13 +05:30
parent 46baeb61e1
commit e938c02748
9 changed files with 42 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
io/bits/poll2.h
View File

@ -33,7 +33,7 @@ extern int __REDIRECT (__poll_chk_warn, (struct pollfd *__fds, nfds_t __nfds,
__poll_chk) __poll_chk)
__warnattr ("poll called with fds buffer too small file nfds entries"); __warnattr ("poll called with fds buffer too small file nfds entries");
__fortify_function __attr_access ((__write_only__, 1, 2)) int __fortify_function __fortified_attr_access (__write_only__, 1, 2) int
poll (struct pollfd *__fds, nfds_t __nfds, int __timeout) poll (struct pollfd *__fds, nfds_t __nfds, int __timeout)
{ {
if (__glibc_objsize (__fds) != (__SIZE_TYPE__) -1) if (__glibc_objsize (__fds) != (__SIZE_TYPE__) -1)
@ -64,7 +64,7 @@ extern int __REDIRECT (__ppoll_chk_warn, (struct pollfd *__fds, nfds_t __nfds,
__ppoll_chk) __ppoll_chk)
__warnattr ("ppoll called with fds buffer too small file nfds entries"); __warnattr ("ppoll called with fds buffer too small file nfds entries");
__fortify_function __attr_access ((__write_only__, 1, 2)) int __fortify_function __fortified_attr_access (__write_only__, 1, 2) int
ppoll (struct pollfd *__fds, nfds_t __nfds, const struct timespec *__timeout, ppoll (struct pollfd *__fds, nfds_t __nfds, const struct timespec *__timeout,
const __sigset_t *__ss) const __sigset_t *__ss)
{ {

6
io/sys/poll.h
View File

@ -52,7 +52,7 @@ __BEGIN_DECLS
This function is a cancellation point and therefore not marked with This function is a cancellation point and therefore not marked with
__THROW. */ __THROW. */
extern int poll (struct pollfd *__fds, nfds_t __nfds, int __timeout) extern int poll (struct pollfd *__fds, nfds_t __nfds, int __timeout)
__attr_access ((__write_only__, 1, 2)); __fortified_attr_access (__write_only__, 1, 2);
#ifdef __USE_GNU #ifdef __USE_GNU
/* Like poll, but before waiting the threads signal mask is replaced /* Like poll, but before waiting the threads signal mask is replaced
@ -64,7 +64,7 @@ extern int poll (struct pollfd *__fds, nfds_t __nfds, int __timeout)
extern int ppoll (struct pollfd *__fds, nfds_t __nfds, extern int ppoll (struct pollfd *__fds, nfds_t __nfds,
const struct timespec *__timeout, const struct timespec *__timeout,
const __sigset_t *__ss) const __sigset_t *__ss)
__attr_access ((__write_only__, 1, 2)); __fortified_attr_access (__write_only__, 1, 2);
# ifdef __USE_TIME_BITS64 # ifdef __USE_TIME_BITS64
# ifdef __REDIRECT # ifdef __REDIRECT
@ -72,7 +72,7 @@ extern int __REDIRECT (ppoll, (struct pollfd *__fds, nfds_t __nfds,
const struct timespec *__timeout, const struct timespec *__timeout,
const __sigset_t *__ss), const __sigset_t *__ss),
__ppoll64) __ppoll64)
__attr_access ((__write_only__, 1, 2)); __fortified_attr_access (__write_only__, 1, 2);
# else # else
# define ppoll __ppoll64 # define ppoll __ppoll64
# endif # endif

4
libio/bits/stdio2.h
View File

@ -258,7 +258,7 @@ extern char *__REDIRECT (__fgets_chk_warn,
__wur __warnattr ("fgets called with bigger size than length " __wur __warnattr ("fgets called with bigger size than length "
"of destination buffer"); "of destination buffer");
__fortify_function __wur __attr_access ((__write_only__, 1, 2)) char * __fortify_function __wur __fortified_attr_access (__write_only__, 1, 2) char *
fgets (char *__restrict __s, int __n, FILE *__restrict __stream) fgets (char *__restrict __s, int __n, FILE *__restrict __stream)
{ {
if (__glibc_objsize (__s) != (size_t) -1) if (__glibc_objsize (__s) != (size_t) -1)
@ -320,7 +320,7 @@ extern char *__REDIRECT (__fgets_unlocked_chk_warn,
__wur __warnattr ("fgets_unlocked called with bigger size than length " __wur __warnattr ("fgets_unlocked called with bigger size than length "
"of destination buffer"); "of destination buffer");
__fortify_function __wur __attr_access ((__write_only__, 1, 2)) char * __fortify_function __wur __fortified_attr_access (__write_only__, 1, 2) char *
fgets_unlocked (char *__restrict __s, int __n, FILE *__restrict __stream) fgets_unlocked (char *__restrict __s, int __n, FILE *__restrict __stream)
{ {
if (__glibc_objsize (__s) != (size_t) -1) if (__glibc_objsize (__s) != (size_t) -1)

4
libio/stdio.h
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@ -590,7 +590,7 @@ extern int putw (int __w, FILE *__stream);
This function is a possible cancellation point and therefore not This function is a possible cancellation point and therefore not
marked with __THROW. */ marked with __THROW. */
extern char *fgets (char *__restrict __s, int __n, FILE *__restrict __stream) extern char *fgets (char *__restrict __s, int __n, FILE *__restrict __stream)
__wur __attr_access ((__write_only__, 1, 2)); __wur __fortified_attr_access (__write_only__, 1, 2);
#if __GLIBC_USE (DEPRECATED_GETS) #if __GLIBC_USE (DEPRECATED_GETS)
/* Get a newline-terminated string from stdin, removing the newline. /* Get a newline-terminated string from stdin, removing the newline.
@ -614,7 +614,7 @@ extern char *gets (char *__s) __wur __attribute_deprecated__;
therefore not marked with __THROW. */ therefore not marked with __THROW. */
extern char *fgets_unlocked (char *__restrict __s, int __n, extern char *fgets_unlocked (char *__restrict __s, int __n,
FILE *__restrict __stream) __wur FILE *__restrict __stream) __wur
__attr_access ((__write_only__, 1, 2)); __fortified_attr_access (__write_only__, 1, 2);
#endif #endif

10
misc/sys/cdefs.h
View File

@ -605,12 +605,22 @@ _Static_assert (0, "IEEE 128-bits long double requires redirection on this platf
size-index is not provided: size-index is not provided:
access (access-mode, <ref-index> [, <size-index>]) */ access (access-mode, <ref-index> [, <size-index>]) */
# define __attr_access(x) __attribute__ ((__access__ x)) # define __attr_access(x) __attribute__ ((__access__ x))
/* For _FORTIFY_SOURCE == 3 we use __builtin_dynamic_object_size, which may
use the access attribute to get object sizes from function definition
arguments, so we can't use them on functions we fortify. Drop the object
size hints for such functions. */
# if __USE_FORTIFY_LEVEL == 3
# define __fortified_attr_access(a, o, s) __attribute__ ((__access__ (a, o)))
# else
# define __fortified_attr_access(a, o, s) __attr_access ((a, o, s))
# endif
# if __GNUC_PREREQ (11, 0) # if __GNUC_PREREQ (11, 0)
# define __attr_access_none(argno) __attribute__ ((__access__ (__none__, argno))) # define __attr_access_none(argno) __attribute__ ((__access__ (__none__, argno)))
# else # else
# define __attr_access_none(argno) # define __attr_access_none(argno)
# endif # endif
#else #else
# define __fortified_attr_access(a, o, s)
# define __attr_access(x) # define __attr_access(x)
# define __attr_access_none(argno) # define __attr_access_none(argno)
#endif #endif

28
posix/unistd.h
View File

@ -369,7 +369,7 @@ extern void closefrom (int __lowfd) __THROW;
This function is a cancellation point and therefore not marked with This function is a cancellation point and therefore not marked with
__THROW. */ __THROW. */
extern ssize_t read (int __fd, void *__buf, size_t __nbytes) __wur extern ssize_t read (int __fd, void *__buf, size_t __nbytes) __wur
__attr_access ((__write_only__, 2, 3)); __fortified_attr_access (__write_only__, 2, 3);
/* Write N bytes of BUF to FD. Return the number written, or -1. /* Write N bytes of BUF to FD. Return the number written, or -1.
@ -388,7 +388,7 @@ extern ssize_t write (int __fd, const void *__buf, size_t __n) __wur
__THROW. */ __THROW. */
extern ssize_t pread (int __fd, void *__buf, size_t __nbytes, extern ssize_t pread (int __fd, void *__buf, size_t __nbytes,
__off_t __offset) __wur __off_t __offset) __wur
__attr_access ((__write_only__, 2, 3)); __fortified_attr_access (__write_only__, 2, 3);
/* Write N bytes of BUF to FD at the given position OFFSET without /* Write N bytes of BUF to FD at the given position OFFSET without
changing the file pointer. Return the number written, or -1. changing the file pointer. Return the number written, or -1.
@ -404,7 +404,7 @@ extern ssize_t pwrite (int __fd, const void *__buf, size_t __n,
extern ssize_t __REDIRECT (pread, (int __fd, void *__buf, size_t __nbytes, extern ssize_t __REDIRECT (pread, (int __fd, void *__buf, size_t __nbytes,
__off64_t __offset), __off64_t __offset),
pread64) __wur pread64) __wur
__attr_access ((__write_only__, 2, 3)); __fortified_attr_access (__write_only__, 2, 3);
extern ssize_t __REDIRECT (pwrite, (int __fd, const void *__buf, extern ssize_t __REDIRECT (pwrite, (int __fd, const void *__buf,
size_t __nbytes, __off64_t __offset), size_t __nbytes, __off64_t __offset),
pwrite64) __wur pwrite64) __wur
@ -421,7 +421,7 @@ extern ssize_t __REDIRECT (pwrite, (int __fd, const void *__buf,
or 0 for EOF. */ or 0 for EOF. */
extern ssize_t pread64 (int __fd, void *__buf, size_t __nbytes, extern ssize_t pread64 (int __fd, void *__buf, size_t __nbytes,
__off64_t __offset) __wur __off64_t __offset) __wur
__attr_access ((__write_only__, 2, 3)); __fortified_attr_access (__write_only__, 2, 3);
/* Write N bytes of BUF to FD at the given position OFFSET without /* Write N bytes of BUF to FD at the given position OFFSET without
changing the file pointer. Return the number written, or -1. */ changing the file pointer. Return the number written, or -1. */
extern ssize_t pwrite64 (int __fd, const void *__buf, size_t __n, extern ssize_t pwrite64 (int __fd, const void *__buf, size_t __n,
@ -642,7 +642,7 @@ extern long int sysconf (int __name) __THROW;
#ifdef __USE_POSIX2 #ifdef __USE_POSIX2
/* Get the value of the string-valued system variable NAME. */ /* Get the value of the string-valued system variable NAME. */
extern size_t confstr (int __name, char *__buf, size_t __len) __THROW extern size_t confstr (int __name, char *__buf, size_t __len) __THROW
__attr_access ((__write_only__, 2, 3)); __fortified_attr_access (__write_only__, 2, 3);
#endif #endif
@ -709,7 +709,7 @@ extern __gid_t getegid (void) __THROW;
the calling process is in. Otherwise, fill in the group IDs the calling process is in. Otherwise, fill in the group IDs
of its supplementary groups in LIST and return the number written. */ of its supplementary groups in LIST and return the number written. */
extern int getgroups (int __size, __gid_t __list[]) __THROW __wur extern int getgroups (int __size, __gid_t __list[]) __THROW __wur
__attr_access ((__write_only__, 2, 1)); __fortified_attr_access (__write_only__, 2, 1);
#ifdef __USE_GNU #ifdef __USE_GNU
/* Return nonzero iff the calling process is in group GID. */ /* Return nonzero iff the calling process is in group GID. */
extern int group_member (__gid_t __gid) __THROW; extern int group_member (__gid_t __gid) __THROW;
@ -801,7 +801,8 @@ extern char *ttyname (int __fd) __THROW;
/* Store at most BUFLEN characters of the pathname of the terminal FD is /* Store at most BUFLEN characters of the pathname of the terminal FD is
open on in BUF. Return 0 on success, otherwise an error number. */ open on in BUF. Return 0 on success, otherwise an error number. */
extern int ttyname_r (int __fd, char *__buf, size_t __buflen) extern int ttyname_r (int __fd, char *__buf, size_t __buflen)
__THROW __nonnull ((2)) __wur __attr_access ((__write_only__, 2, 3)); __THROW __nonnull ((2)) __wur
__fortified_attr_access (__write_only__, 2, 3);
/* Return 1 if FD is a valid descriptor associated /* Return 1 if FD is a valid descriptor associated
with a terminal, zero if not. */ with a terminal, zero if not. */
@ -836,7 +837,8 @@ extern int symlink (const char *__from, const char *__to)
Returns the number of characters read, or -1 for errors. */ Returns the number of characters read, or -1 for errors. */
extern ssize_t readlink (const char *__restrict __path, extern ssize_t readlink (const char *__restrict __path,
char *__restrict __buf, size_t __len) char *__restrict __buf, size_t __len)
__THROW __nonnull ((1, 2)) __wur __attr_access ((__write_only__, 2, 3)); __THROW __nonnull ((1, 2)) __wur
__fortified_attr_access (__write_only__, 2, 3);
#endif /* Use POSIX.1-2001. */ #endif /* Use POSIX.1-2001. */
@ -848,7 +850,8 @@ extern int symlinkat (const char *__from, int __tofd,
/* Like readlink but a relative PATH is interpreted relative to FD. */ /* Like readlink but a relative PATH is interpreted relative to FD. */
extern ssize_t readlinkat (int __fd, const char *__restrict __path, extern ssize_t readlinkat (int __fd, const char *__restrict __path,
char *__restrict __buf, size_t __len) char *__restrict __buf, size_t __len)
__THROW __nonnull ((2, 3)) __wur __attr_access ((__write_only__, 3, 4)); __THROW __nonnull ((2, 3)) __wur
__fortified_attr_access (__write_only__, 3, 4);
#endif #endif
/* Remove the link NAME. */ /* Remove the link NAME. */
@ -884,7 +887,7 @@ extern char *getlogin (void);
This function is a possible cancellation point and therefore not This function is a possible cancellation point and therefore not
marked with __THROW. */ marked with __THROW. */
extern int getlogin_r (char *__name, size_t __name_len) __nonnull ((1)) extern int getlogin_r (char *__name, size_t __name_len) __nonnull ((1))
__attr_access ((__write_only__, 1, 2)); __fortified_attr_access (__write_only__, 1, 2);
#endif #endif
#ifdef __USE_MISC #ifdef __USE_MISC
@ -906,7 +909,7 @@ extern int setlogin (const char *__name) __THROW __nonnull ((1));
The result is null-terminated if LEN is large enough for the full The result is null-terminated if LEN is large enough for the full
name and the terminator. */ name and the terminator. */
extern int gethostname (char *__name, size_t __len) __THROW __nonnull ((1)) extern int gethostname (char *__name, size_t __len) __THROW __nonnull ((1))
__attr_access ((__write_only__, 1, 2)); __fortified_attr_access (__write_only__, 1, 2);
#endif #endif
@ -925,7 +928,8 @@ extern int sethostid (long int __id) __THROW __wur;
Called just like `gethostname' and `sethostname'. Called just like `gethostname' and `sethostname'.
The NIS domain name is usually the empty string when not using NIS. */ The NIS domain name is usually the empty string when not using NIS. */
extern int getdomainname (char *__name, size_t __len) extern int getdomainname (char *__name, size_t __len)
__THROW __nonnull ((1)) __wur __attr_access ((__write_only__, 1, 2)); __THROW __nonnull ((1)) __wur
__fortified_attr_access (__write_only__, 1, 2);
extern int setdomainname (const char *__name, size_t __len) extern int setdomainname (const char *__name, size_t __len)
__THROW __nonnull ((1)) __wur __attr_access ((__read_only__, 1, 2)); __THROW __nonnull ((1)) __wur __attr_access ((__read_only__, 1, 2));

5
stdlib/stdlib.h
View File

@ -943,7 +943,8 @@ extern size_t mbstowcs (wchar_t *__restrict __pwcs,
extern size_t wcstombs (char *__restrict __s, extern size_t wcstombs (char *__restrict __s,
const wchar_t *__restrict __pwcs, size_t __n) const wchar_t *__restrict __pwcs, size_t __n)
__THROW __THROW
__attr_access ((__write_only__, 1, 3)) __attr_access ((__read_only__, 2)); __fortified_attr_access (__write_only__, 1, 3)
__attr_access ((__read_only__, 2));
#ifdef __USE_MISC #ifdef __USE_MISC
/* Determine whether the string value of RESPONSE matches the affirmation /* Determine whether the string value of RESPONSE matches the affirmation
@ -997,7 +998,7 @@ extern char *ptsname (int __fd) __THROW __wur;
terminal associated with the master FD is open on in BUF. terminal associated with the master FD is open on in BUF.
Return 0 on success, otherwise an error number. */ Return 0 on success, otherwise an error number. */
extern int ptsname_r (int __fd, char *__buf, size_t __buflen) extern int ptsname_r (int __fd, char *__buf, size_t __buflen)
__THROW __nonnull ((2)) __attr_access ((__write_only__, 2, 3)); __THROW __nonnull ((2)) __fortified_attr_access (__write_only__, 2, 3);
/* Open a master pseudo terminal and return its file descriptor. */ /* Open a master pseudo terminal and return its file descriptor. */
extern int getpt (void); extern int getpt (void);

5
string/bits/string_fortified.h
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@ -64,7 +64,7 @@ __NTH (memset (void *__dest, int __ch, size_t __len))
# include <bits/strings_fortified.h> # include <bits/strings_fortified.h>
void __explicit_bzero_chk (void *__dest, size_t __len, size_t __destlen) void __explicit_bzero_chk (void *__dest, size_t __len, size_t __destlen)
__THROW __nonnull ((1)) __attr_access ((__write_only__, 1, 2)); __THROW __nonnull ((1)) __fortified_attr_access (__write_only__, 1, 2);
__fortify_function void __fortify_function void
__NTH (explicit_bzero (void *__dest, size_t __len)) __NTH (explicit_bzero (void *__dest, size_t __len))
@ -106,7 +106,8 @@ __NTH (stpncpy (char *__dest, const char *__src, size_t __n))
#else #else
extern char *__stpncpy_chk (char *__dest, const char *__src, size_t __n, extern char *__stpncpy_chk (char *__dest, const char *__src, size_t __n,
size_t __destlen) __THROW size_t __destlen) __THROW
__attr_access ((__write_only__, 1, 3)) __attr_access ((__read_only__, 2)); __fortified_attr_access ((__write_only__, 1, 3))
__attr_access ((__read_only__, 2));
extern char *__REDIRECT_NTH (__stpncpy_alias, (char *__dest, const char *__src, extern char *__REDIRECT_NTH (__stpncpy_alias, (char *__dest, const char *__src,
size_t __n), stpncpy); size_t __n), stpncpy);

2
string/string.h
View File

@ -448,7 +448,7 @@ extern char *strerror_l (int __errnum, locale_t __l) __THROW;
/* Set N bytes of S to 0. The compiler will not delete a call to this /* Set N bytes of S to 0. The compiler will not delete a call to this
function, even if S is dead after the call. */ function, even if S is dead after the call. */
extern void explicit_bzero (void *__s, size_t __n) __THROW __nonnull ((1)) extern void explicit_bzero (void *__s, size_t __n) __THROW __nonnull ((1))
__attr_access ((__write_only__, 1, 2)); __fortified_attr_access (__write_only__, 1, 2);
/* Return the next DELIM-delimited token from *STRINGP, /* Return the next DELIM-delimited token from *STRINGP,
terminating it with a '\0', and update *STRINGP to point past it. */ terminating it with a '\0', and update *STRINGP to point past it. */