support/support_can_chroot.c

   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 stat64 before;
  33   xstat ("/dev", &before);
  34   if (chroot ("/dev") != 0)
  35     {
  36       *result = errno;
  37       return;
  38     }
  39   struct stat64 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 }