debug/vsnprintf_chk.c

   1 /* Copyright (C) 1991, 1995, 1997, 1998, 2004, 2006, 2009
   2    Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <stdarg.h>
  21 #include <stdio.h>
  22 #include "../libio/libioP.h"
  23 #include "../libio/strfile.h"
  24
  25 extern const struct _IO_jump_t _IO_strn_jumps attribute_hidden;
  26
  27 /* Write formatted output into S, according to the format
  28    string FORMAT, writing no more than MAXLEN characters.  */
  29 /* VARARGS5 */
  30 int
  31 ___vsnprintf_chk (char *s, size_t maxlen, int flags, size_t slen,
  32                   const char *format, va_list args)
  33 {
  34   /* XXX Maybe for less strict version do not fail immediately.
  35      Though, maxlen is supposed to be the size of buffer pointed
  36      to by s, so a conforming program can't pass such maxlen
  37      to *snprintf.  */
  38   if (__builtin_expect (slen < maxlen, 0))
  39     __chk_fail ();
  40
  41   _IO_strnfile sf;
  42   int ret;
  43 #ifdef _IO_MTSAFE_IO
  44   sf.f._sbf._f._lock = NULL;
  45 #endif
  46
  47   /* We need to handle the special case where MAXLEN is 0.  Use the
  48      overflow buffer right from the start.  */
  49   if (maxlen == 0)
  50     {
  51       s = sf.overflow_buf;
  52       maxlen = sizeof (sf.overflow_buf);
  53     }
  54
  55   _IO_no_init (&sf.f._sbf._f, _IO_USER_LOCK, -1, NULL, NULL);
  56   _IO_JUMPS (&sf.f._sbf) = &_IO_strn_jumps;
  57   s[0] = '\0';
  58
  59   /* For flags > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
  60      can only come from read-only format strings.  */
  61   if (flags > 0)
  62     sf.f._sbf._f._flags2 |= _IO_FLAGS2_FORTIFY;
  63
  64   _IO_str_init_static_internal (&sf.f, s, maxlen - 1, s);
  65   ret = INTUSE(_IO_vfprintf) (&sf.f._sbf._f, format, args);
  66
  67   if (sf.f._sbf._f._IO_buf_base != sf.overflow_buf)
  68     *sf.f._sbf._f._IO_write_ptr = '\0';
  69   return ret;
  70 }
  71 ldbl_hidden_def (___vsnprintf_chk, __vsnprintf_chk)
  72 ldbl_strong_alias (___vsnprintf_chk, __vsnprintf_chk)