debug/pread_chk.c

   1 /* Copyright (C) 2005 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 <unistd.h>
  20 #include <sys/param.h>
  21
  22
  23 ssize_t
  24 __pread_chk (int fd, void *buf, size_t nbytes, off_t offset, size_t buflen)
  25 {
  26   /* In case NBYTES is greater than BUFLEN, we read BUFLEN+1 bytes.
  27      This might overflow the buffer but the damage is reduced to just
  28      one byte.  And the program will terminate right away.  */
  29   ssize_t n = __pread (fd, buf, offset, MIN (nbytes, buflen + 1));
  30   if (n > 0 && (size_t) n > buflen)
  31     __chk_fail ();
  32   return n;
  33 }