Patchwork [7/9] Use PRINTF_FORTIFY instead of _IO_FLAGS2_FORTIFY.

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Submitter Zack Weinberg
Date March 7, 2018, 7:32 p.m.
Message ID <20180307193205.4751-8-zackw@panix.com>
Download mbox | patch
Permalink /patch/26235/
State New
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Comments

Zack Weinberg - March 7, 2018, 7:32 p.m.
The _chk variants of all of the printf functions become much simpler.
This is the last thing that we needed _IO_acquire_lock_clear_flags2
for, so it can go as well.  I took the opportunity to make the headers
included and the names of all local variables consistent across all the
affected files.

Since we ultimately want to get rid of __no_long_double as well, it
must be possible to get all of the nontrivial effects of the _chk
functions by calling the _internal functions with appropriate flags.
For most of the __(v)xprintf_chk functions, this is covered by
PRINTF_FORTIFY plus some up-front argument checks that can be
duplicated.  However, __(v)sprintf_chk installs a custom jump table so
that it can crash instead of overflowing the output buffer.  This
functionality is moved to __vsprintf_internal, which now has a
'maxlen' argument like __vsnprintf_internal; to get the unsafe
behavior of ordinary (v)sprintf, pass -1 for that argument.

obstack_printf_chk and obstack_vprintf_chk are no longer in the same
file.

	* libio/iovsprintf.c (_IO_str_chk_overflow, _IO_str_chk_jumps):
	Moved here from debug/vsprintf_chk.c.
	(__vsprintf_internal): Add 'maxlen' argument.  Change the setup
	and completion logic for the strfile to match exactly what
	__vsprintf_chk used to do, except, when maxlen is -1, pass -1 to
	_IO_str_init_static_internal instead of maxlen-1.
	(__vsprintf): Pass -1 as maxlen to __vsprintf_internal.
	* stdio-common/sprintf.c (__sprintf): Pass -1 as maxlen to
	__vsprintf_internal.
	* libio/libioP.h: Update prototype of __vsprintf_internal and add
	a comment explaining why it has the maxlen argument.

	* debug/vsprintf_chk.c (__vsprintf_chk)
	* debug/sprintf_chk.c (__sprintf_chk):
	Directly call __vsprintf_internal, passing PRINTF_FORTIFY if
	'flags' argument is positive, and slen as maxlen.  No need to lock
	the FILE and/or construct a temporary FILE.  Minimize and normalize
	header inclusions and variable names.  Do not libc_hidden_def anything.

	* debug/asprintf_chk.c (__asprintf_chk)
	* debug/dprintf_chk.c (__dprintf_chk)
	* debug/fprintf_chk.c (__fprintf_chk)
	* debug/fwprintf_chk.c (__fwprintf_chk)
	* debug/obprintf_chk.c (__obstack_printf_chk, __obstack_vprintf_chk)
	* debug/printf_chk.c (__printf_chk)
	* debug/snprintf_chk.c (__snprintf_chk)
	* debug/swprintf_chk.c (__swprintf_chk)
	* debug/vasprintf_chk.c (__vasprintf_chk)
	* debug/vdprintf_chk.c (__vdprintf_chk)
	* debug/vfprintf_chk.c (__vfprintf_chk)
	* debug/vfwprintf_chk.c (__vfwprintf_chk)
	* debug/vprintf_chk.c (__vprintf_chk)
	* debug/vsnprintf_chk.c (__vsnprintf_chk)
	* debug/vswprintf_chk.c (__vswprintf_chk)
	* debug/vwprintf_chk.c (__vwprintf_chk)
	* debug/wprintf_chk.c (__wprintf_chk):
	Directly call the corresponding vxxprintf_internal function, passing
	PRINTF_FORTIFY if 'flag' argument is positive.	No need to lock
	the FILE and/or construct a temporary FILE.  Minimize and normalize
	header inclusions and variable names.  Do not libc_hidden_def anything.

	* debug/obprintf_chk.c (__obstack_vprintf_chk): Move to new file...
	* debug/vobprintf_chk.c: ... here.
	* debug/Makefile (routines): Add vobprintf_chk.

	* sysdeps/ieee754/ldbl-opt/nldbl-compat.c
	(__nldbl___vsprintf): Pass -1 as maxlen to __vsprintf_internal.
	(__nldbl___vfprintf_chk, __nldbl___vsnprintf_chk)
	(__nldbl___vsprintf_chk, __nldbl___vswprintf_chk)
	(__nldbl___vasprintf_chk, __nldbl___vdprintf_chk)
	(__nldbl___obstack_vfprintf_chk):
	Directly call the corresponding vxxprintf_internal function,
	passing PRINTF_FORTIFY if 'flag' argument is positive.  If necessary,
	duplicate comparison of slen with 0 or maxlen from the corresponding
	non-__nldbl function.

	* include/stdio.h (__vsnprintf_chk, __vfprintf_chk, __vasprintf_chk)
	(__vdprintf_chk, __obstack_vfprintf_chk): Remove libc_hidden_proto.
	* include/wchar.h (__vfwprintf_chk, __vswprintf_chk):
	Remove libc_hidden_proto.

	* stdio-common/vfprintf-internal.c
	(__vfprintf_internal, __vfwprintf_internal):
	Do not check _IO_FLAGS2_FORTIFY.
	* libio/libio.h (_IO_FLAGS2_FORTIFY): Remove.
	* libio/libioP.h (_IO_acquire_lock_clear_flags2_fct): Remove.
	(_IO_acquire_lock_clear_flags2): Remove.
	(_IO_release_lock): Remove conditional statement which will
	now never execute.
	(_IO_acquire_lock): Remove variable which is now unused.
	* sysdeps/generic/stdio-lock.h (_IO_acquire_lock_clear_flags2): Remove.
	* sysdeps/nptl/stdio-lock.h (_IO_acquire_lock_clear_flags2): Remove.
---
 debug/Makefile                          |  2 +-
 debug/asprintf_chk.c                    | 20 +++----
 debug/dprintf_chk.c                     | 20 +++----
 debug/fprintf_chk.c                     | 20 +++----
 debug/fwprintf_chk.c                    | 20 +++----
 debug/obprintf_chk.c                    | 96 ++++-----------------------------
 debug/printf_chk.c                      | 20 +++----
 debug/snprintf_chk.c                    | 24 +++++----
 debug/sprintf_chk.c                     | 25 +++++----
 debug/swprintf_chk.c                    | 27 ++++++----
 debug/vasprintf_chk.c                   | 68 ++---------------------
 debug/vdprintf_chk.c                    | 37 ++-----------
 debug/vfprintf_chk.c                    | 21 ++------
 debug/vfwprintf_chk.c                   | 21 ++------
 debug/vobprintf_chk.c                   | 32 +++++++++++
 debug/vprintf_chk.c                     | 20 ++-----
 debug/vsnprintf_chk.c                   | 46 +++-------------
 debug/vsprintf_chk.c                    | 69 +++---------------------
 debug/vswprintf_chk.c                   | 51 +++---------------
 debug/vwprintf_chk.c                    | 21 ++------
 debug/wprintf_chk.c                     | 21 +++-----
 include/stdio.h                         |  5 --
 include/wchar.h                         |  2 -
 libio/iovsprintf.c                      | 54 +++++++++++++++++--
 libio/libio.h                           |  1 -
 libio/libioP.h                          | 25 +++------
 stdio-common/sprintf.c                  |  2 +-
 stdio-common/vfprintf-internal.c        |  2 -
 sysdeps/generic/stdio-lock.h            |  7 ---
 sysdeps/ieee754/ldbl-opt/nldbl-compat.c | 32 +++++++----
 sysdeps/nptl/stdio-lock.h               |  7 ---
 31 files changed, 268 insertions(+), 550 deletions(-)
 create mode 100644 debug/vobprintf_chk.c

Patch

diff --git a/debug/Makefile b/debug/Makefile
index c6f6feb0ec..f4153bb98d 100644
--- a/debug/Makefile
+++ b/debug/Makefile
@@ -45,7 +45,7 @@  routines  = backtrace backtracesyms backtracesymsfd noophooks \
 	    gethostname_chk getdomainname_chk wcrtomb_chk mbsnrtowcs_chk \
 	    wcsnrtombs_chk mbsrtowcs_chk wcsrtombs_chk mbstowcs_chk \
 	    wcstombs_chk asprintf_chk vasprintf_chk dprintf_chk \
-	    vdprintf_chk obprintf_chk \
+	    vdprintf_chk obprintf_chk vobprintf_chk \
 	    longjmp_chk ____longjmp_chk \
 	    fdelt_chk poll_chk ppoll_chk \
 	    explicit_bzero_chk \
diff --git a/debug/asprintf_chk.c b/debug/asprintf_chk.c
index 9cd4143f2e..eb885c35ca 100644
--- a/debug/asprintf_chk.c
+++ b/debug/asprintf_chk.c
@@ -15,22 +15,24 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <libioP.h>
 #include <stdarg.h>
-#include <stdio.h>
+#include <libio/libioP.h>
 
 
 /* Write formatted output from FORMAT to a string which is
    allocated with malloc and stored in *STRING_PTR.  */
 int
-__asprintf_chk (char **result_ptr, int flags, const char *format, ...)
+__asprintf_chk (char **result_ptr, int flag, const char *format, ...)
 {
-  va_list arg;
-  int done;
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
+  va_list ap;
+  int ret;
 
-  va_start (arg, format);
-  done = __vasprintf_chk (result_ptr, flags, format, arg);
-  va_end (arg);
+  va_start (ap, format);
+  ret = __vasprintf_internal (result_ptr, format, ap, mode);
+  va_end (ap);
 
-  return done;
+  return ret;
 }
diff --git a/debug/dprintf_chk.c b/debug/dprintf_chk.c
index df3867c61c..b5c62827c0 100644
--- a/debug/dprintf_chk.c
+++ b/debug/dprintf_chk.c
@@ -15,21 +15,23 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <libioP.h>
 #include <stdarg.h>
-#include <stdio.h>
+#include <libio/libioP.h>
 
 
 /* Write formatted output to D, according to the format string FORMAT.  */
 int
-__dprintf_chk (int d, int flags, const char *format, ...)
+__dprintf_chk (int d, int flag, const char *format, ...)
 {
-  va_list arg;
-  int done;
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
+  va_list ap;
+  int ret;
 
-  va_start (arg, format);
-  done = __vdprintf_chk (d, flags, format, arg);
-  va_end (arg);
+  va_start (ap, format);
+  ret = __vdprintf_internal (d, format, ap, mode);
+  va_end (ap);
 
-  return done;
+  return ret;
 }
diff --git a/debug/fprintf_chk.c b/debug/fprintf_chk.c
index cff4438afb..14afc073b2 100644
--- a/debug/fprintf_chk.c
+++ b/debug/fprintf_chk.c
@@ -16,29 +16,23 @@ 
    <http://www.gnu.org/licenses/>.  */
 
 #include <stdarg.h>
-#include <stdio.h>
-#include "../libio/libioP.h"
+#include <libio/libioP.h>
 
 
 /* Write formatted output to FP from the format string FORMAT.  */
 int
 ___fprintf_chk (FILE *fp, int flag, const char *format, ...)
 {
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
   va_list ap;
-  int done;
-
-  _IO_acquire_lock_clear_flags2 (fp);
-  if (flag > 0)
-    fp->_flags2 |= _IO_FLAGS2_FORTIFY;
+  int ret;
 
   va_start (ap, format);
-  done = vfprintf (fp, format, ap);
+  ret = __vfprintf_internal (fp, format, ap, mode);
   va_end (ap);
 
-  if (flag > 0)
-    fp->_flags2 &= ~_IO_FLAGS2_FORTIFY;
-  _IO_release_lock (fp);
-
-  return done;
+  return ret;
 }
 ldbl_strong_alias (___fprintf_chk, __fprintf_chk)
diff --git a/debug/fwprintf_chk.c b/debug/fwprintf_chk.c
index 63167c1839..10d84ce98b 100644
--- a/debug/fwprintf_chk.c
+++ b/debug/fwprintf_chk.c
@@ -16,28 +16,22 @@ 
    <http://www.gnu.org/licenses/>.  */
 
 #include <stdarg.h>
-#include <wchar.h>
-#include "../libio/libioP.h"
+#include <libio/libioP.h>
 
 
 /* Write formatted output to FP from the format string FORMAT.  */
 int
 __fwprintf_chk (FILE *fp, int flag, const wchar_t *format, ...)
 {
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
   va_list ap;
-  int done;
-
-  _IO_acquire_lock_clear_flags2 (fp);
-  if (flag > 0)
-    fp->_flags2 |= _IO_FLAGS2_FORTIFY;
+  int ret;
 
   va_start (ap, format);
-  done = __vfwprintf_internal (fp, format, ap, 0);
+  ret = __vfwprintf_internal (fp, format, ap, mode);
   va_end (ap);
 
-  if (flag > 0)
-    fp->_flags2 &= ~_IO_FLAGS2_FORTIFY;
-  _IO_release_lock (fp);
-
-  return done;
+  return ret;
 }
diff --git a/debug/obprintf_chk.c b/debug/obprintf_chk.c
index 41dd481c34..c1a8f9e9a9 100644
--- a/debug/obprintf_chk.c
+++ b/debug/obprintf_chk.c
@@ -17,99 +17,23 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-
-#include <stdlib.h>
-#include <libioP.h>
-#include "../libio/strfile.h"
-#include <assert.h>
-#include <string.h>
-#include <errno.h>
-#include <obstack.h>
+#include <libio/libioP.h>
 #include <stdarg.h>
-#include <stdio_ext.h>
-
-
-struct _IO_obstack_file
-{
-  struct _IO_FILE_plus file;
-  struct obstack *obstack;
-};
-
-extern const struct _IO_jump_t _IO_obstack_jumps libio_vtable attribute_hidden;
-
-int
-__obstack_vprintf_chk (struct obstack *obstack, int flags, const char *format,
-		       va_list args)
-{
-  struct obstack_FILE
-    {
-      struct _IO_obstack_file ofile;
-    } new_f;
-  int result;
-  int size;
-  int room;
-
-#ifdef _IO_MTSAFE_IO
-  new_f.ofile.file.file._lock = NULL;
-#endif
-
-  _IO_no_init (&new_f.ofile.file.file, _IO_USER_LOCK, -1, NULL, NULL);
-  _IO_JUMPS (&new_f.ofile.file) = &_IO_obstack_jumps;
-  room = obstack_room (obstack);
-  size = obstack_object_size (obstack) + room;
-  if (size == 0)
-    {
-      /* We have to handle the allocation a bit different since the
-	 `_IO_str_init_static' function would handle a size of zero
-	 different from what we expect.  */
-
-      /* Get more memory.  */
-      obstack_make_room (obstack, 64);
-
-      /* Recompute how much room we have.  */
-      room = obstack_room (obstack);
-      size = room;
-
-      assert (size != 0);
-    }
-
-  _IO_str_init_static_internal ((struct _IO_strfile_ *) &new_f.ofile,
-				obstack_base (obstack),
-				size, obstack_next_free (obstack));
-  /* Now allocate the rest of the current chunk.  */
-  assert (size == (new_f.ofile.file.file._IO_write_end
-		   - new_f.ofile.file.file._IO_write_base));
-  assert (new_f.ofile.file.file._IO_write_ptr
-	  == (new_f.ofile.file.file._IO_write_base
-	      + obstack_object_size (obstack)));
-  obstack_blank_fast (obstack, room);
-
-  new_f.ofile.obstack = obstack;
-
-  /* For flags > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
-     can only come from read-only format strings.  */
-  if (flags > 0)
-    new_f.ofile.file.file._flags2 |= _IO_FLAGS2_FORTIFY;
-
-  result = __vfprintf_internal (&new_f.ofile.file.file, format, args, 0);
-
-  /* Shrink the buffer to the space we really currently need.  */
-  obstack_blank_fast (obstack, (new_f.ofile.file.file._IO_write_ptr
-				- new_f.ofile.file.file._IO_write_end));
-
-  return result;
-}
-libc_hidden_def (__obstack_vprintf_chk)
 
 
 int
-__obstack_printf_chk (struct obstack *obstack, int flags, const char *format,
+__obstack_printf_chk (struct obstack *obstack, int flag, const char *format,
 		      ...)
 {
-  int result;
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
   va_list ap;
+  int ret;
+
   va_start (ap, format);
-  result = __obstack_vprintf_chk (obstack, flags, format, ap);
+  ret = __obstack_vprintf_internal (obstack, format, ap, mode);
   va_end (ap);
-  return result;
+
+  return ret;
 }
diff --git a/debug/printf_chk.c b/debug/printf_chk.c
index 426dc78386..e035b42590 100644
--- a/debug/printf_chk.c
+++ b/debug/printf_chk.c
@@ -16,29 +16,23 @@ 
    <http://www.gnu.org/licenses/>.  */
 
 #include <stdarg.h>
-#include <stdio.h>
-#include "../libio/libioP.h"
+#include <libio/libioP.h>
 
 
 /* Write formatted output to stdout from the format string FORMAT.  */
 int
 ___printf_chk (int flag, const char *format, ...)
 {
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
   va_list ap;
-  int done;
-
-  _IO_acquire_lock_clear_flags2 (stdout);
-  if (flag > 0)
-    stdout->_flags2 |= _IO_FLAGS2_FORTIFY;
+  int ret;
 
   va_start (ap, format);
-  done = vfprintf (stdout, format, ap);
+  ret = __vfprintf_internal (stdout, format, ap, mode);
   va_end (ap);
 
-  if (flag > 0)
-    stdout->_flags2 &= ~_IO_FLAGS2_FORTIFY;
-  _IO_release_lock (stdout);
-
-  return done;
+  return ret;
 }
 ldbl_strong_alias (___printf_chk, __printf_chk)
diff --git a/debug/snprintf_chk.c b/debug/snprintf_chk.c
index cddba37109..984b5e8932 100644
--- a/debug/snprintf_chk.c
+++ b/debug/snprintf_chk.c
@@ -15,25 +15,29 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <libioP.h>
 #include <stdarg.h>
-#include <stdio.h>
+#include <libio/libioP.h>
 
 
 /* Write formatted output into S, according to the format
    string FORMAT, writing no more than MAXLEN characters.  */
-/* VARARGS5 */
 int
-___snprintf_chk (char *s, size_t maxlen, int flags, size_t slen,
+___snprintf_chk (char *s, size_t maxlen, int flag, size_t slen,
 		 const char *format, ...)
 {
-  va_list arg;
-  int done;
+  if (__glibc_unlikely (slen < maxlen))
+    __chk_fail ();
 
-  va_start (arg, format);
-  done = __vsnprintf_chk (s, maxlen, flags, slen, format, arg);
-  va_end (arg);
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
+  va_list ap;
+  int ret;
 
-  return done;
+  va_start (ap, format);
+  ret = __vsnprintf_internal (s, maxlen, format, ap, mode);
+  va_end (ap);
+
+  return ret;
 }
 ldbl_strong_alias (___snprintf_chk, __snprintf_chk)
diff --git a/debug/sprintf_chk.c b/debug/sprintf_chk.c
index 78214563dd..649e8ab4d5 100644
--- a/debug/sprintf_chk.c
+++ b/debug/sprintf_chk.c
@@ -15,22 +15,27 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <libioP.h>
 #include <stdarg.h>
-#include <stdio.h>
+#include <libio/libioP.h>
+
 
 /* Write formatted output into S, according to the format string FORMAT.  */
-/* VARARGS4 */
 int
-___sprintf_chk (char *s, int flags, size_t slen, const char *format, ...)
+___sprintf_chk (char *s, int flag, size_t slen, const char *format, ...)
 {
-  va_list arg;
-  int done;
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
+  va_list ap;
+  int ret;
+
+  if (slen == 0)
+    __chk_fail ();
 
-  va_start (arg, format);
-  done = __vsprintf_chk (s, flags, slen, format, arg);
-  va_end (arg);
+  va_start (ap, format);
+  ret = __vsprintf_internal (s, slen, format, ap, mode);
+  va_end (ap);
 
-  return done;
+  return ret;
 }
 ldbl_strong_alias (___sprintf_chk, __sprintf_chk)
diff --git a/debug/swprintf_chk.c b/debug/swprintf_chk.c
index 35887e48e2..186c17751c 100644
--- a/debug/swprintf_chk.c
+++ b/debug/swprintf_chk.c
@@ -16,20 +16,27 @@ 
    <http://www.gnu.org/licenses/>.  */
 
 #include <stdarg.h>
-#include <wchar.h>
+#include <libio/libioP.h>
 
-/* Write formatted output into S, according to the format string FORMAT.  */
-/* VARARGS5 */
+
+/* Write formatted output into S, according to the format string FORMAT,
+   writing no more than MAXLEN characters.  */
 int
-__swprintf_chk (wchar_t *s, size_t n, int flag, size_t s_len,
+__swprintf_chk (wchar_t *s, size_t maxlen, int flag, size_t slen,
 		const wchar_t *format, ...)
 {
-  va_list arg;
-  int done;
+  if (__glibc_unlikely (slen < maxlen))
+    __chk_fail ();
+
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
+  va_list ap;
+  int ret;
 
-  va_start (arg, format);
-  done = __vswprintf_chk (s, n, flag, s_len, format, arg);
-  va_end (arg);
+  va_start (ap, format);
+  ret = __vswprintf_internal (s, maxlen, format, ap, mode);
+  va_end (ap);
 
-  return done;
+  return ret;
 }
diff --git a/debug/vasprintf_chk.c b/debug/vasprintf_chk.c
index 6136694431..f5975ea02a 100644
--- a/debug/vasprintf_chk.c
+++ b/debug/vasprintf_chk.c
@@ -24,72 +24,14 @@ 
    This exception applies to code released by its copyright holders
    in files containing the exception.  */
 
-#include <malloc.h>
-#include <string.h>
-#include <stdio.h>
-#include <stdio_ext.h>
-#include "../libio/libioP.h"
-#include "../libio/strfile.h"
+#include <libio/libioP.h>
 
 int
-__vasprintf_chk (char **result_ptr, int flags, const char *format,
-		 va_list args)
+__vasprintf_chk (char **result_ptr, int flag, const char *format, va_list ap)
 {
-  /* Initial size of the buffer to be used.  Will be doubled each time an
-     overflow occurs.  */
-  const size_t init_string_size = 100;
-  char *string;
-  _IO_strfile sf;
-  int ret;
-  size_t needed;
-  size_t allocated;
-  /* No need to clear the memory here (unlike for open_memstream) since
-     we know we will never seek on the stream.  */
-  string = (char *) malloc (init_string_size);
-  if (string == NULL)
-    return -1;
-#ifdef _IO_MTSAFE_IO
-  sf._sbf._f._lock = NULL;
-#endif
-  _IO_no_init (&sf._sbf._f, _IO_USER_LOCK, -1, NULL, NULL);
-  _IO_JUMPS (&sf._sbf) = &_IO_str_jumps;
-  _IO_str_init_static_internal (&sf, string, init_string_size, string);
-  sf._sbf._f._flags &= ~_IO_USER_BUF;
-  sf._s._allocate_buffer = (_IO_alloc_type) malloc;
-  sf._s._free_buffer = (_IO_free_type) free;
-
-  /* For flags > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
      can only come from read-only format strings.  */
-  if (flags > 0)
-    sf._sbf._f._flags2 |= _IO_FLAGS2_FORTIFY;
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
 
-  ret = __vfprintf_internal (&sf._sbf._f, format, args, 0);
-  if (ret < 0)
-    {
-      free (sf._sbf._f._IO_buf_base);
-      return ret;
-    }
-  /* Only use realloc if the size we need is of the same (binary)
-     order of magnitude then the memory we allocated.  */
-  needed = sf._sbf._f._IO_write_ptr - sf._sbf._f._IO_write_base + 1;
-  allocated = sf._sbf._f._IO_write_end - sf._sbf._f._IO_write_base;
-  if ((allocated >> 1) <= needed)
-    *result_ptr = (char *) realloc (sf._sbf._f._IO_buf_base, needed);
-  else
-    {
-      *result_ptr = (char *) malloc (needed);
-      if (*result_ptr != NULL)
-	{
-	  memcpy (*result_ptr, sf._sbf._f._IO_buf_base, needed - 1);
-	  free (sf._sbf._f._IO_buf_base);
-	}
-      else
-	/* We have no choice, use the buffer we already have.  */
-	*result_ptr = (char *) realloc (sf._sbf._f._IO_buf_base, needed);
-    }
-  if (*result_ptr == NULL)
-    *result_ptr = sf._sbf._f._IO_buf_base;
-  (*result_ptr)[needed - 1] = '\0';
-  return ret;
+  return __vasprintf_internal (result_ptr, format, ap, mode);
 }
-libc_hidden_def (__vasprintf_chk)
diff --git a/debug/vdprintf_chk.c b/debug/vdprintf_chk.c
index 4386127cfe..e04514e355 100644
--- a/debug/vdprintf_chk.c
+++ b/debug/vdprintf_chk.c
@@ -24,41 +24,14 @@ 
    This exception applies to code released by its copyright holders
    in files containing the exception.  */
 
-#include <libioP.h>
-#include <stdio_ext.h>
+#include <libio/libioP.h>
 
 int
-__vdprintf_chk (int d, int flags, const char *format, va_list arg)
+__vdprintf_chk (int d, int flag, const char *format, va_list ap)
 {
-  struct _IO_FILE_plus tmpfil;
-  struct _IO_wide_data wd;
-  int done;
-
-#ifdef _IO_MTSAFE_IO
-  tmpfil.file._lock = NULL;
-#endif
-  _IO_no_init (&tmpfil.file, _IO_USER_LOCK, 0, &wd, &_IO_wfile_jumps);
-  _IO_JUMPS (&tmpfil) = &_IO_file_jumps;
-  _IO_new_file_init_internal (&tmpfil);
-  if (_IO_file_attach (&tmpfil.file, d) == NULL)
-    {
-      _IO_un_link (&tmpfil);
-      return EOF;
-    }
-  tmpfil.file._flags |= _IO_DELETE_DONT_CLOSE;
-
-  _IO_mask_flags (&tmpfil.file, _IO_NO_READS,
-		  _IO_NO_READS+_IO_NO_WRITES+_IO_IS_APPENDING);
-
-  /* For flags > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
      can only come from read-only format strings.  */
-  if (flags > 0)
-    tmpfil.file._flags2 |= _IO_FLAGS2_FORTIFY;
-
-  done = __vfprintf_internal (&tmpfil.file, format, arg, 0);
-
-  _IO_FINISH (&tmpfil.file);
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
 
-  return done;
+  return __vdprintf_internal (d, format, ap, mode);
 }
-libc_hidden_def (__vdprintf_chk)
diff --git a/debug/vfprintf_chk.c b/debug/vfprintf_chk.c
index 5babbf611e..44426e14fd 100644
--- a/debug/vfprintf_chk.c
+++ b/debug/vfprintf_chk.c
@@ -15,28 +15,17 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <stdarg.h>
-#include <stdio.h>
-#include "../libio/libioP.h"
+#include <libio/libioP.h>
 
 
 /* Write formatted output to FP from the format string FORMAT.  */
 int
 ___vfprintf_chk (FILE *fp, int flag, const char *format, va_list ap)
 {
-  int done;
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
 
-  _IO_acquire_lock_clear_flags2 (fp);
-  if (flag > 0)
-    fp->_flags2 |= _IO_FLAGS2_FORTIFY;
-
-  done = vfprintf (fp, format, ap);
-
-  if (flag > 0)
-    fp->_flags2 &= ~_IO_FLAGS2_FORTIFY;
-  _IO_release_lock (fp);
-
-  return done;
+  return __vfprintf_internal (fp, format, ap, mode);
 }
-ldbl_hidden_def (___vfprintf_chk, __vfprintf_chk)
 ldbl_strong_alias (___vfprintf_chk, __vfprintf_chk)
diff --git a/debug/vfwprintf_chk.c b/debug/vfwprintf_chk.c
index abf2bd6517..3aed308156 100644
--- a/debug/vfwprintf_chk.c
+++ b/debug/vfwprintf_chk.c
@@ -15,27 +15,16 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <stdarg.h>
-#include <wchar.h>
-#include "../libio/libioP.h"
+#include <libio/libioP.h>
 
 
 /* Write formatted output to FP from the format string FORMAT.  */
 int
 __vfwprintf_chk (FILE *fp, int flag, const wchar_t *format, va_list ap)
 {
-  int done;
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
 
-  _IO_acquire_lock_clear_flags2 (fp);
-  if (flag > 0)
-    fp->_flags2 |= _IO_FLAGS2_FORTIFY;
-
-  done = __vfwprintf_internal (fp, format, ap, 0);
-
-  if (flag > 0)
-    fp->_flags2 &= ~_IO_FLAGS2_FORTIFY;
-  _IO_release_lock (fp);
-
-  return done;
+  return __vfwprintf_internal (fp, format, ap, mode);
 }
-libc_hidden_def (__vfwprintf_chk)
diff --git a/debug/vobprintf_chk.c b/debug/vobprintf_chk.c
new file mode 100644
index 0000000000..edfbe8f00a
--- /dev/null
+++ b/debug/vobprintf_chk.c
@@ -0,0 +1,32 @@ 
+/* Print output of stream to given obstack.
+   Copyright (C) 1996-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
+
+   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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <libio/libioP.h>
+
+
+int
+__obstack_vprintf_chk (struct obstack *obstack, int flag, const char *format,
+		       va_list ap)
+{
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
+
+  return __obstack_vprintf_internal (obstack, format, ap, mode);
+}
diff --git a/debug/vprintf_chk.c b/debug/vprintf_chk.c
index b3b2c53df2..69fcb721ac 100644
--- a/debug/vprintf_chk.c
+++ b/debug/vprintf_chk.c
@@ -15,27 +15,17 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <stdarg.h>
-#include <stdio.h>
-#include "../libio/libioP.h"
+#include <libio/libioP.h>
 
 
 /* Write formatted output to stdout from the format string FORMAT.  */
 int
 ___vprintf_chk (int flag, const char *format, va_list ap)
 {
-  int done;
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
 
-  _IO_acquire_lock_clear_flags2 (stdout);
-  if (flag > 0)
-    stdout->_flags2 |= _IO_FLAGS2_FORTIFY;
-
-  done = vfprintf (stdout, format, ap);
-
-  if (flag > 0)
-    stdout->_flags2 &= ~_IO_FLAGS2_FORTIFY;
-  _IO_release_lock (stdout);
-
-  return done;
+  return __vfprintf_internal (stdout, format, ap, mode);
 }
 ldbl_strong_alias (___vprintf_chk, __vprintf_chk)
diff --git a/debug/vsnprintf_chk.c b/debug/vsnprintf_chk.c
index 95d286f416..666a83b701 100644
--- a/debug/vsnprintf_chk.c
+++ b/debug/vsnprintf_chk.c
@@ -15,56 +15,22 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <stdarg.h>
-#include <stdio.h>
-#include "../libio/libioP.h"
-#include "../libio/strfile.h"
+#include <libio/libioP.h>
 
-extern const struct _IO_jump_t _IO_strn_jumps libio_vtable attribute_hidden;
 
 /* Write formatted output into S, according to the format
    string FORMAT, writing no more than MAXLEN characters.  */
-/* VARARGS5 */
 int
-___vsnprintf_chk (char *s, size_t maxlen, int flags, size_t slen,
-		  const char *format, va_list args)
+___vsnprintf_chk (char *s, size_t maxlen, int flag, size_t slen,
+		  const char *format, va_list ap)
 {
-  /* XXX Maybe for less strict version do not fail immediately.
-     Though, maxlen is supposed to be the size of buffer pointed
-     to by s, so a conforming program can't pass such maxlen
-     to *snprintf.  */
   if (__glibc_unlikely (slen < maxlen))
     __chk_fail ();
 
-  _IO_strnfile sf;
-  int ret;
-#ifdef _IO_MTSAFE_IO
-  sf.f._sbf._f._lock = NULL;
-#endif
-
-  /* We need to handle the special case where MAXLEN is 0.  Use the
-     overflow buffer right from the start.  */
-  if (maxlen == 0)
-    {
-      s = sf.overflow_buf;
-      maxlen = sizeof (sf.overflow_buf);
-    }
-
-  _IO_no_init (&sf.f._sbf._f, _IO_USER_LOCK, -1, NULL, NULL);
-  _IO_JUMPS (&sf.f._sbf) = &_IO_strn_jumps;
-  s[0] = '\0';
-
-  /* For flags > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
      can only come from read-only format strings.  */
-  if (flags > 0)
-    sf.f._sbf._f._flags2 |= _IO_FLAGS2_FORTIFY;
-
-  _IO_str_init_static_internal (&sf.f, s, maxlen - 1, s);
-  ret = __vfprintf_internal (&sf.f._sbf._f, format, args, 0);
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
 
-  if (sf.f._sbf._f._IO_buf_base != sf.overflow_buf)
-    *sf.f._sbf._f._IO_write_ptr = '\0';
-  return ret;
+  return __vsnprintf_internal (s, maxlen, format, ap, mode);
 }
-ldbl_hidden_def (___vsnprintf_chk, __vsnprintf_chk)
 ldbl_strong_alias (___vsnprintf_chk, __vsnprintf_chk)
diff --git a/debug/vsprintf_chk.c b/debug/vsprintf_chk.c
index 53f07236ae..c1b1a8da4f 100644
--- a/debug/vsprintf_chk.c
+++ b/debug/vsprintf_chk.c
@@ -15,75 +15,20 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <stdarg.h>
-#include <stdio.h>
-#include "../libio/libioP.h"
-#include "../libio/strfile.h"
-
-
-static int _IO_str_chk_overflow (FILE *fp, int c) __THROW;
-
-static int
-_IO_str_chk_overflow (FILE *fp, int c)
-{
-  /* When we come to here this means the user supplied buffer is
-     filled.  */
-  __chk_fail ();
-}
-
-
-static const struct _IO_jump_t _IO_str_chk_jumps libio_vtable =
-{
-  JUMP_INIT_DUMMY,
-  JUMP_INIT(finish, _IO_str_finish),
-  JUMP_INIT(overflow, _IO_str_chk_overflow),
-  JUMP_INIT(underflow, _IO_str_underflow),
-  JUMP_INIT(uflow, _IO_default_uflow),
-  JUMP_INIT(pbackfail, _IO_str_pbackfail),
-  JUMP_INIT(xsputn, _IO_default_xsputn),
-  JUMP_INIT(xsgetn, _IO_default_xsgetn),
-  JUMP_INIT(seekoff, _IO_str_seekoff),
-  JUMP_INIT(seekpos, _IO_default_seekpos),
-  JUMP_INIT(setbuf, _IO_default_setbuf),
-  JUMP_INIT(sync, _IO_default_sync),
-  JUMP_INIT(doallocate, _IO_default_doallocate),
-  JUMP_INIT(read, _IO_default_read),
-  JUMP_INIT(write, _IO_default_write),
-  JUMP_INIT(seek, _IO_default_seek),
-  JUMP_INIT(close, _IO_default_close),
-  JUMP_INIT(stat, _IO_default_stat),
-  JUMP_INIT(showmanyc, _IO_default_showmanyc),
-  JUMP_INIT(imbue, _IO_default_imbue)
-};
-
+#include <libio/libioP.h>
 
 int
-___vsprintf_chk (char *s, int flags, size_t slen, const char *format,
-		 va_list args)
+___vsprintf_chk (char *s, int flag, size_t slen, const char *format,
+		 va_list ap)
 {
-  _IO_strfile f;
-  int ret;
-#ifdef _IO_MTSAFE_IO
-  f._sbf._f._lock = NULL;
-#endif
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
 
   if (slen == 0)
     __chk_fail ();
 
-  _IO_no_init (&f._sbf._f, _IO_USER_LOCK, -1, NULL, NULL);
-  _IO_JUMPS (&f._sbf) = &_IO_str_chk_jumps;
-  s[0] = '\0';
-  _IO_str_init_static_internal (&f, s, slen - 1, s);
-
-  /* For flags > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
-     can only come from read-only format strings.  */
-  if (flags > 0)
-    f._sbf._f._flags2 |= _IO_FLAGS2_FORTIFY;
-
-  ret = __vfprintf_internal (&f._sbf._f, format, args, 0);
-
-  *f._sbf._f._IO_write_ptr = '\0';
-  return ret;
+  return __vsprintf_internal (s, slen, format, ap, mode);
 }
 ldbl_hidden_def (___vsprintf_chk, __vsprintf_chk)
 ldbl_strong_alias (___vsprintf_chk, __vsprintf_chk)
diff --git a/debug/vswprintf_chk.c b/debug/vswprintf_chk.c
index 4d616f8835..2c6fadd463 100644
--- a/debug/vswprintf_chk.c
+++ b/debug/vswprintf_chk.c
@@ -15,60 +15,21 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <stdarg.h>
-#include <wchar.h>
-#include "../libio/libioP.h"
-#include "../libio/strfile.h"
+#include <libio/libioP.h>
 
 
 /* Write formatted output into S, according to the format
    string FORMAT, writing no more than MAXLEN characters.  */
-/* VARARGS5 */
 int
-__vswprintf_chk (wchar_t *s, size_t maxlen, int flags, size_t slen,
-		 const wchar_t *format, va_list args)
+__vswprintf_chk (wchar_t *s, size_t maxlen, int flag, size_t slen,
+		 const wchar_t *format, va_list ap)
 {
-  /* XXX Maybe for less strict version do not fail immediately.
-     Though, maxlen is supposed to be the size of buffer pointed
-     to by s, so a conforming program can't pass such maxlen
-     to *snprintf.  */
   if (__glibc_unlikely (slen < maxlen))
     __chk_fail ();
 
-  _IO_wstrnfile sf;
-  struct _IO_wide_data wd;
-  int ret;
-#ifdef _IO_MTSAFE_IO
-  sf.f._sbf._f._lock = NULL;
-#endif
-
-  /* We need to handle the special case where MAXLEN is 0.  Use the
-     overflow buffer right from the start.  */
-  if (__glibc_unlikely (maxlen == 0))
-    /* Since we have to write at least the terminating L'\0' a buffer
-       length of zero always makes the function fail.  */
-    return -1;
-
-  _IO_no_init (&sf.f._sbf._f, _IO_USER_LOCK, 0, &wd, &_IO_wstrn_jumps);
-  _IO_fwide (&sf.f._sbf._f, 1);
-  s[0] = L'\0';
-
-  /* For flags > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
      can only come from read-only format strings.  */
-  if (flags > 0)
-    sf.f._sbf._f._flags2 |= _IO_FLAGS2_FORTIFY;
-
-  _IO_wstr_init_static (&sf.f._sbf._f, s, maxlen - 1, s);
-  ret = __vfwprintf_internal ((FILE *) &sf.f._sbf, format, args, 0);
-
-  if (sf.f._sbf._f._wide_data->_IO_buf_base == sf.overflow_buf)
-    /* ISO C99 requires swprintf/vswprintf to return an error if the
-       output does not fit int he provided buffer.  */
-    return -1;
-
-  /* Terminate the string.  */
-  *sf.f._sbf._f._wide_data->_IO_write_ptr = '\0';
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
 
-  return ret;
+  return __vswprintf_internal (s, maxlen, format, ap, mode);
 }
-libc_hidden_def (__vswprintf_chk)
diff --git a/debug/vwprintf_chk.c b/debug/vwprintf_chk.c
index fedc7a46bf..f1e8878a54 100644
--- a/debug/vwprintf_chk.c
+++ b/debug/vwprintf_chk.c
@@ -15,27 +15,16 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <stdarg.h>
-#include <stdio.h>
-#include <wchar.h>
-#include "../libio/libioP.h"
+#include <libio/libioP.h>
 
 
 /* Write formatted output to stdout from the format string FORMAT.  */
 int
 __vwprintf_chk (int flag, const wchar_t *format, va_list ap)
 {
-  int done;
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
 
-  _IO_acquire_lock_clear_flags2 (stdout);
-  if (flag > 0)
-    stdout->_flags2 |= _IO_FLAGS2_FORTIFY;
-
-  done = __vfwprintf_internal (stdout, format, ap, 0);
-
-  if (flag > 0)
-    stdout->_flags2 &= ~_IO_FLAGS2_FORTIFY;
-  _IO_release_lock (stdout);
-
-  return done;
+  return __vfwprintf_internal (stdout, format, ap, mode);
 }
diff --git a/debug/wprintf_chk.c b/debug/wprintf_chk.c
index 819050e5af..9f406e95f8 100644
--- a/debug/wprintf_chk.c
+++ b/debug/wprintf_chk.c
@@ -16,29 +16,22 @@ 
    <http://www.gnu.org/licenses/>.  */
 
 #include <stdarg.h>
-#include <stdio.h>
-#include <wchar.h>
-#include "../libio/libioP.h"
+#include <libio/libioP.h>
 
 
 /* Write formatted output to stdout from the format string FORMAT.  */
 int
 __wprintf_chk (int flag, const wchar_t *format, ...)
 {
+  /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
+     can only come from read-only format strings.  */
+  unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
   va_list ap;
-  int done;
-
-  _IO_acquire_lock_clear_flags2 (stdout);
-  if (flag > 0)
-    stdout->_flags2 |= _IO_FLAGS2_FORTIFY;
+  int ret;
 
   va_start (ap, format);
-  done = __vfwprintf_internal (stdout, format, ap, 0);
+  ret = __vfwprintf_internal (stdout, format, ap, mode);
   va_end (ap);
 
-  if (flag > 0)
-    stdout->_flags2 &= ~_IO_FLAGS2_FORTIFY;
-  _IO_release_lock (stdout);
-
-  return done;
+  return ret;
 }
diff --git a/include/stdio.h b/include/stdio.h
index 93b9385524..22fc916470 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -203,11 +203,6 @@  libc_hidden_proto (__open_memstream)
 libc_hidden_proto (__libc_fatal)
 rtld_hidden_proto (__libc_fatal)
 libc_hidden_proto (__vsprintf_chk)
-libc_hidden_proto (__vsnprintf_chk)
-libc_hidden_proto (__vfprintf_chk)
-libc_hidden_proto (__vasprintf_chk)
-libc_hidden_proto (__vdprintf_chk)
-libc_hidden_proto (__obstack_vprintf_chk)
 
 extern FILE * __fmemopen (void *buf, size_t len, const char *mode);
 libc_hidden_proto (__fmemopen)
diff --git a/include/wchar.h b/include/wchar.h
index 1db0ac8278..90b6e43f18 100644
--- a/include/wchar.h
+++ b/include/wchar.h
@@ -226,8 +226,6 @@  extern int __vswprintf_chk (wchar_t *__restrict __s, size_t __n,
 			    const wchar_t *__restrict __format,
 			    __gnuc_va_list __arg)
      /* __attribute__ ((__format__ (__wprintf__, 5, 0))) */;
-libc_hidden_proto (__vfwprintf_chk)
-libc_hidden_proto (__vswprintf_chk)
 
 extern int __isoc99_fwscanf (__FILE *__restrict __stream,
 			     const wchar_t *__restrict __format, ...);
diff --git a/libio/iovsprintf.c b/libio/iovsprintf.c
index cf4b9973a7..513ca03013 100644
--- a/libio/iovsprintf.c
+++ b/libio/iovsprintf.c
@@ -27,8 +27,47 @@ 
 #include "libioP.h"
 #include "strfile.h"
 
+static int __THROW
+_IO_str_chk_overflow (FILE *fp, int c)
+{
+  /* If we get here, the user-supplied buffer would be overrun by
+     further output.  */
+  __chk_fail ();
+}
+
+static const struct _IO_jump_t _IO_str_chk_jumps libio_vtable =
+{
+  JUMP_INIT_DUMMY,
+  JUMP_INIT(finish, _IO_str_finish),
+  JUMP_INIT(overflow, _IO_str_chk_overflow),
+  JUMP_INIT(underflow, _IO_str_underflow),
+  JUMP_INIT(uflow, _IO_default_uflow),
+  JUMP_INIT(pbackfail, _IO_str_pbackfail),
+  JUMP_INIT(xsputn, _IO_default_xsputn),
+  JUMP_INIT(xsgetn, _IO_default_xsgetn),
+  JUMP_INIT(seekoff, _IO_str_seekoff),
+  JUMP_INIT(seekpos, _IO_default_seekpos),
+  JUMP_INIT(setbuf, _IO_default_setbuf),
+  JUMP_INIT(sync, _IO_default_sync),
+  JUMP_INIT(doallocate, _IO_default_doallocate),
+  JUMP_INIT(read, _IO_default_read),
+  JUMP_INIT(write, _IO_default_write),
+  JUMP_INIT(seek, _IO_default_seek),
+  JUMP_INIT(close, _IO_default_close),
+  JUMP_INIT(stat, _IO_default_stat),
+  JUMP_INIT(showmanyc, _IO_default_showmanyc),
+  JUMP_INIT(imbue, _IO_default_imbue)
+};
+
+/* This function is called by regular vsprintf with maxlen set to -1,
+   and by vsprintf_chk with maxlen set to the size of the output
+   string.  In the former case, _IO_str_chk_overflow will never be
+   called; in the latter case it will crash the program if the buffer
+   overflows.  */
+
 int
-__vsprintf_internal (char *string, const char *format, va_list args,
+__vsprintf_internal (char *string, size_t maxlen,
+                     const char *format, va_list args,
                      unsigned int mode_flags)
 {
   _IO_strfile sf;
@@ -38,17 +77,22 @@  __vsprintf_internal (char *string, const char *format, va_list args,
   sf._sbf._f._lock = NULL;
 #endif
   _IO_no_init (&sf._sbf._f, _IO_USER_LOCK, -1, NULL, NULL);
-  _IO_JUMPS (&sf._sbf) = &_IO_str_jumps;
-  _IO_str_init_static_internal (&sf, string, -1, string);
+  _IO_JUMPS (&sf._sbf) = &_IO_str_chk_jumps;
+  string[0] = '\0';
+  _IO_str_init_static_internal (&sf, string,
+                                (maxlen == -1) ? -1 : maxlen - 1,
+                                string);
+
   ret = __vfprintf_internal (&sf._sbf._f, format, args, mode_flags);
-  _IO_putc_unlocked ('\0', &sf._sbf._f);
+
+  *sf._sbf._f._IO_write_ptr = '\0';
   return ret;
 }
 
 int
 __vsprintf (char *string, const char *format, va_list args)
 {
-  return __vsprintf_internal (string, format, args, 0);
+  return __vsprintf_internal (string, -1, format, args, 0);
 }
 
 ldbl_strong_alias (__vsprintf, _IO_vsprintf)
diff --git a/libio/libio.h b/libio/libio.h
index 1025f3343e..68dac44635 100644
--- a/libio/libio.h
+++ b/libio/libio.h
@@ -90,7 +90,6 @@  typedef union
 /* Bits for the _flags2 field.  */
 #define _IO_FLAGS2_MMAP 1
 #define _IO_FLAGS2_NOTCANCEL 2
-#define _IO_FLAGS2_FORTIFY 4
 #define _IO_FLAGS2_USER_WBUF 8
 #define _IO_FLAGS2_NOCLOSE 32
 #define _IO_FLAGS2_CLOEXEC 64
diff --git a/libio/libioP.h b/libio/libioP.h
index 17eda383d3..07b60e3e26 100644
--- a/libio/libioP.h
+++ b/libio/libioP.h
@@ -672,8 +672,13 @@  extern int __vdprintf_internal (int d, const char *format, va_list ap,
 extern int __obstack_vprintf_internal (struct obstack *ob, const char *fmt,
                                        va_list ap, unsigned int mode_flags);
 
-extern int __vsprintf_internal (char *string, const char *format, va_list ap,
+/* Note: __vsprintf_internal, unlike vsprintf, does take a maxlen argument,
+   because it's called by both vsprintf and vsprintf_chk.  If maxlen is
+   not set to -1, overrunning the buffer will cause a prompt crash.  */
+extern int __vsprintf_internal (char *string, size_t maxlen,
+                                const char *format, va_list ap,
                                 unsigned int mode_flags);
+
 extern int __vsnprintf_internal (char *string, size_t maxlen,
                                  const char *format, va_list ap,
                                  unsigned int mode_flags);
@@ -788,26 +793,10 @@  _IO_acquire_lock_fct (FILE **p)
     _IO_funlockfile (fp);
 }
 
-static inline void
-__attribute__ ((__always_inline__))
-_IO_acquire_lock_clear_flags2_fct (FILE **p)
-{
-  FILE *fp = *p;
-  fp->_flags2 &= ~(_IO_FLAGS2_FORTIFY);
-  if ((fp->_flags & _IO_USER_LOCK) == 0)
-    _IO_funlockfile (fp);
-}
-
 #if !defined _IO_MTSAFE_IO && IS_IN (libc)
 # define _IO_acquire_lock(_fp)						      \
-  do {									      \
-    FILE *_IO_acquire_lock_file = NULL
-# define _IO_acquire_lock_clear_flags2(_fp)				      \
-  do {									      \
-    FILE *_IO_acquire_lock_file = (_fp)
+  do {
 # define _IO_release_lock(_fp)						      \
-    if (_IO_acquire_lock_file != NULL)					      \
-      _IO_acquire_lock_file->_flags2 &= ~(_IO_FLAGS2_FORTIFY);		      \
   } while (0)
 #endif
 
diff --git a/stdio-common/sprintf.c b/stdio-common/sprintf.c
index 77423b292f..447faa4e25 100644
--- a/stdio-common/sprintf.c
+++ b/stdio-common/sprintf.c
@@ -27,7 +27,7 @@  __sprintf (char *s, const char *format, ...)
   int done;
 
   va_start (arg, format);
-  done = __vsprintf_internal (s, format, arg, 0);
+  done = __vsprintf_internal (s, -1, format, arg, 0);
   va_end (arg);
 
   return done;
diff --git a/stdio-common/vfprintf-internal.c b/stdio-common/vfprintf-internal.c
index d8716f4f07..e2f44b74f3 100644
--- a/stdio-common/vfprintf-internal.c
+++ b/stdio-common/vfprintf-internal.c
@@ -1285,8 +1285,6 @@  vfprintf (FILE *s, const CHAR_T *format, va_list ap, unsigned int mode_flags)
   /* Temporarily honor environmental settings.  */
   if (__ldbl_is_dbl)
     mode_flags |= PRINTF_LDBL_IS_DBL;
-  if (s->_flags2 & _IO_FLAGS2_FORTIFY)
-    mode_flags |= PRINTF_FORTIFY;
 
   /* Orient the stream.  */
 #ifdef ORIENT
diff --git a/sysdeps/generic/stdio-lock.h b/sysdeps/generic/stdio-lock.h
index 4a40618545..25ccd07f29 100644
--- a/sysdeps/generic/stdio-lock.h
+++ b/sysdeps/generic/stdio-lock.h
@@ -54,15 +54,8 @@  __libc_lock_define_recursive (typedef, _IO_lock_t)
 	__attribute__((cleanup (_IO_acquire_lock_fct)))			      \
 	= (_fp);							      \
     _IO_flockfile (_IO_acquire_lock_file);
-#  define _IO_acquire_lock_clear_flags2(_fp) \
-  do {									      \
-    FILE *_IO_acquire_lock_file						      \
-	__attribute__((cleanup (_IO_acquire_lock_clear_flags2_fct)))	      \
-	= (_fp);							      \
-    _IO_flockfile (_IO_acquire_lock_file);
 # else
 #  define _IO_acquire_lock(_fp) _IO_acquire_lock_needs_exceptions_enabled
-#  define _IO_acquire_lock_clear_flags2(_fp) _IO_acquire_lock (_fp)
 # endif
 # define _IO_release_lock(_fp) ; } while (0)
 
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-compat.c b/sysdeps/ieee754/ldbl-opt/nldbl-compat.c
index f00eb55eb5..f29c28e888 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-compat.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-compat.c
@@ -178,7 +178,7 @@  __nldbl___vsprintf (char *string, const char *fmt, va_list ap)
 {
   int done;
   __no_long_double = 1;
-  done = __vsprintf_internal (string, fmt, ap, 0);
+  done = __vsprintf_internal (string, -1, fmt, ap, 0);
   __no_long_double = 0;
   return done;
 }
@@ -578,7 +578,7 @@  __nldbl___vfprintf_chk (FILE *s, int flag, const char *fmt, va_list ap)
 {
   int res;
   set_no_long_double ();
-  res = __vfprintf_chk (s, flag, fmt, ap);
+  res = __vfprintf_internal (s, fmt, ap, (flag > 0) ? PRINTF_FORTIFY : 0);
   clear_no_long_double ();
   return res;
 }
@@ -590,7 +590,7 @@  __nldbl___vfwprintf_chk (FILE *s, int flag, const wchar_t *fmt, va_list ap)
 {
   int res;
   set_no_long_double ();
-  res = __vfwprintf_chk (s, flag, fmt, ap);
+  res = __vfwprintf_internal (s, fmt, ap, (flag > 0) ? PRINTF_FORTIFY : 0);
   clear_no_long_double ();
   return res;
 }
@@ -608,9 +608,13 @@  attribute_compat_text_section
 __nldbl___vsnprintf_chk (char *string, size_t maxlen, int flag, size_t slen,
 			 const char *fmt, va_list ap)
 {
+  if (__glibc_unlikely (slen < maxlen))
+    __chk_fail ();
+
   int res;
   __no_long_double = 1;
-  res = __vsnprintf_chk (string, maxlen, flag, slen, fmt, ap);
+  res = __vsnprintf_internal (string, maxlen, fmt, ap,
+			      (flag > 0) ? PRINTF_FORTIFY : 0);
   __no_long_double = 0;
   return res;
 }
@@ -621,9 +625,13 @@  attribute_compat_text_section
 __nldbl___vsprintf_chk (char *string, int flag, size_t slen, const char *fmt,
 			va_list ap)
 {
+  if (slen == 0)
+    __chk_fail ();
+
   int res;
   __no_long_double = 1;
-  res = __vsprintf_chk (string, flag, slen, fmt, ap);
+  res = __vsprintf_internal (string, slen, fmt, ap,
+			     (flag > 0) ? PRINTF_FORTIFY : 0);
   __no_long_double = 0;
   return res;
 }
@@ -634,9 +642,13 @@  attribute_compat_text_section
 __nldbl___vswprintf_chk (wchar_t *string, size_t maxlen, int flag, size_t slen,
 			 const wchar_t *fmt, va_list ap)
 {
+  if (__glibc_unlikely (slen < maxlen))
+    __chk_fail ();
+
   int res;
   __no_long_double = 1;
-  res = __vswprintf_chk (string, maxlen, flag, slen, fmt, ap);
+  res = __vswprintf_internal (string, maxlen, fmt, ap,
+			      (flag > 0) ? PRINTF_FORTIFY : 0);
   __no_long_double = 0;
   return res;
 }
@@ -669,7 +681,8 @@  __nldbl___vasprintf_chk (char **ptr, int flag, const char *fmt, va_list arg)
 {
   int res;
   __no_long_double = 1;
-  res = __vasprintf_chk (ptr, flag, fmt, arg);
+  res = __vasprintf_internal (ptr, fmt, arg,
+			      (flag > 0) ? PRINTF_FORTIFY : 0);
   __no_long_double = 0;
   return res;
 }
@@ -695,7 +708,7 @@  __nldbl___vdprintf_chk (int d, int flag, const char *fmt, va_list arg)
 {
   int res;
   set_no_long_double ();
-  res = __vdprintf_chk (d, flag, fmt, arg);
+  res = __vdprintf_internal (d, fmt, arg, (flag > 0) ? PRINTF_FORTIFY : 0);
   clear_no_long_double ();
   return res;
 }
@@ -722,7 +735,8 @@  __nldbl___obstack_vprintf_chk (struct obstack *obstack, int flag,
 {
   int res;
   __no_long_double = 1;
-  res = __obstack_vprintf_chk (obstack, flag, fmt, arg);
+  res = __obstack_vprintf_internal (obstack, fmt, arg,
+				    (flag > 0) ? PRINTF_FORTIFY : 0);
   __no_long_double = 0;
   return res;
 }
diff --git a/sysdeps/nptl/stdio-lock.h b/sysdeps/nptl/stdio-lock.h
index 5b9782452f..1d6a81c5bf 100644
--- a/sysdeps/nptl/stdio-lock.h
+++ b/sysdeps/nptl/stdio-lock.h
@@ -94,15 +94,8 @@  typedef struct { int lock; int cnt; void *owner; } _IO_lock_t;
 	__attribute__((cleanup (_IO_acquire_lock_fct)))			      \
 	= (_fp);							      \
     _IO_flockfile (_IO_acquire_lock_file);
-#  define _IO_acquire_lock_clear_flags2(_fp) \
-  do {									      \
-    FILE *_IO_acquire_lock_file						      \
-	__attribute__((cleanup (_IO_acquire_lock_clear_flags2_fct)))	      \
-	= (_fp);							      \
-    _IO_flockfile (_IO_acquire_lock_file);
 # else
 #  define _IO_acquire_lock(_fp) _IO_acquire_lock_needs_exceptions_enabled
-#  define _IO_acquire_lock_clear_flags2(_fp) _IO_acquire_lock (_fp)
 # endif
 # define _IO_release_lock(_fp) ; } while (0)