debug/realpath_chk.c

   1 /* Copyright (C) 2005-2023 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 #include <errno.h>
  23
  24
  25 char *
  26 __realpath_chk (const char *buf, char *resolved, size_t resolvedlen)
  27 {
  28 #ifdef PATH_MAX
  29   if (resolvedlen < PATH_MAX)
  30     __chk_fail ();
  31
  32   return __realpath (buf, resolved);
  33 #else
  34   long int pathmax;
  35
  36   if (buf == NULL)
  37     {
  38       __set_errno (EINVAL);
  39       return NULL;
  40     }
  41
  42   pathmax = __pathconf (buf, _PC_PATH_MAX);
  43   if (pathmax != -1)
  44     {
  45       /* We do have a fixed limit.  */
  46       if (resolvedlen < pathmax)
  47         __chk_fail ();
  48
  49       return __realpath (buf, resolved);
  50     }
  51
  52   /* Since there is no fixed limit we check whether the size is large
  53      enough.  */
  54   char *res = __realpath (buf, NULL);
  55   if (res != NULL)
  56     {
  57       size_t actlen = strlen (res) + 1;
  58       if (actlen > resolvedlen)
  59         __chk_fail ();
  60
  61       memcpy (resolved, res, actlen);
  62       free (res);
  63       res = resolved;
  64     }
  65
  66   return res;
  67 #endif
  68 }