debug/realpath_chk.c

   1 /* Copyright (C) 2005-2019 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, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <limits.h>
  19 #include <stdlib.h>
  20 #include <string.h>
  21 #include <unistd.h>
  22
  23
  24 char *
  25 __realpath_chk (const char *buf, char *resolved, size_t resolvedlen)
  26 {
  27 #ifdef PATH_MAX
  28   if (resolvedlen < PATH_MAX)
  29     __chk_fail ();
  30
  31   return __realpath (buf, resolved);
  32 #else
  33   long int pathmax =__pathconf (buf, _PC_PATH_MAX);
  34   if (pathmax != -1)
  35     {
  36       /* We do have a fixed limit.  */
  37       if (resolvedlen < pathmax)
  38         __chk_fail ();
  39
  40       return __realpath (buf, resolved);
  41     }
  42
  43   /* Since there is no fixed limit we check whether the size is large
  44      enough.  */
  45   char *res = __realpath (buf, NULL);
  46   if (res != NULL)
  47     {
  48       size_t actlen = strlen (res) + 1;
  49       if (actlen > resolvedlen)
  50         __chk_fail ();
  51
  52       memcpy (resolved, res, actlen);
  53       free (res);
  54       res = resolved;
  55     }
  56
  57   return res;
  58 #endif
  59 }