1  /* Return true if the process can perform a chroot operation.
       2     Copyright (C) 2017-2023 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, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #include <errno.h>
      20  #include <stdio.h>
      21  #include <support/check.h>
      22  #include <support/namespace.h>
      23  #include <support/support.h>
      24  #include <support/xunistd.h>
      25  #include <sys/stat.h>
      26  #include <unistd.h>
      27  
      28  static void
      29  callback (void *closure)
      30  {
      31    int *result = closure;
      32    struct stat before;
      33    xstat ("/dev", &before);
      34    if (chroot ("/dev") != 0)
      35      {
      36        *result = errno;
      37        return;
      38      }
      39    struct stat after;
      40    xstat ("/", &after);
      41    TEST_VERIFY (before.st_dev == after.st_dev);
      42    TEST_VERIFY (before.st_ino == after.st_ino);
      43    *result = 0;
      44  }
      45  
      46  bool
      47  support_can_chroot (void)
      48  {
      49    int *result = support_shared_allocate (sizeof (*result));
      50    *result = 0;
      51    support_isolate_in_subprocess (callback, result);
      52    bool ok = *result == 0;
      53    if (!ok)
      54      {
      55        static bool already_warned;
      56        if (!already_warned)
      57          {
      58            already_warned = true;
      59            errno = *result;
      60            printf ("warning: this process does not support chroot: %m\n");
      61          }
      62      }
      63    support_shared_free (result);
      64    return ok;
      65  }