debug/vsnprintf_chk.c

   1 /* Copyright (C) 1991, 1995, 1997, 1998, 2004 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <stdarg.h>
  20 #include <stdio.h>
  21 #include "../libio/libioP.h"
  22 #include "../libio/strfile.h"
  23
  24 extern const struct _IO_jump_t _IO_strn_jumps attribute_hidden;
  25
  26 /* Write formatted output into S, according to the format
  27    string FORMAT, writing no more than MAXLEN characters.  */
  28 /* VARARGS5 */
  29 int
  30 __vsnprintf_chk (char *s, size_t maxlen, int flags, size_t slen,
  31                  const char *format, va_list args)
  32 {
  33   /* XXX Maybe for less strict version do not fail immediately.
  34      Though, maxlen is supposed to be the size of buffer pointed
  35      to by s, so a conforming program can't pass such maxlen
  36      to *snprintf.  */
  37   if (__builtin_expect (slen < maxlen, 0))
  38     __chk_fail ();
  39
  40   _IO_strnfile sf;
  41   int ret;
  42 #ifdef _IO_MTSAFE_IO
  43   sf.f._sbf._f._lock = NULL;
  44 #endif
  45
  46   /* We need to handle the special case where MAXLEN is 0.  Use the
  47      overflow buffer right from the start.  */
  48   if (maxlen == 0)
  49     {
  50       s = sf.overflow_buf;
  51       maxlen = sizeof (sf.overflow_buf);
  52     }
  53
  54   _IO_no_init (&sf.f._sbf._f, _IO_USER_LOCK, -1, NULL, NULL);
  55   _IO_JUMPS ((struct _IO_FILE_plus *) &sf.f._sbf) = &_IO_strn_jumps;
  56   s[0] = '\0';
  57
  58   /* For flags > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
  59      can only come from read-only format strings.  */
  60   if (flags > 0)
  61     sf.f._sbf._f._flags2 |= _IO_FLAGS2_FORTIFY;
  62
  63   _IO_str_init_static_internal (&sf.f, s, maxlen - 1, s);
  64   ret = INTUSE(_IO_vfprintf) ((_IO_FILE *) &sf.f._sbf, format, args);
  65
  66   if (sf.f._sbf._f._IO_buf_base != sf.overflow_buf)
  67     *sf.f._sbf._f._IO_write_ptr = '\0';
  68   return ret;
  69 }
  70 libc_hidden_def (__vsnprintf_chk)