1  /* Enter a mount namespace.
       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 <support/namespace.h>
      20  
      21  #include <sched.h>
      22  #include <stdio.h>
      23  #ifdef CLONE_NEWNS
      24  # include <sys/mount.h>
      25  #endif /* CLONE_NEWNS */
      26  
      27  bool
      28  support_enter_mount_namespace (void)
      29  {
      30  #ifdef CLONE_NEWNS
      31    if (unshare (CLONE_NEWNS) == 0)
      32      {
      33        /* On some systems, / is marked as MS_SHARED, which means that
      34           mounts within the namespace leak to the rest of the system,
      35           which is not what we want.  */
      36        if (mount ("none", "/", NULL, MS_REC | MS_PRIVATE, NULL) != 0)
      37          {
      38            printf ("warning: making the mount namespace private failed: %m\n");
      39            return false;
      40          }
      41        return true;
      42      }
      43    else
      44      printf ("warning: unshare (CLONE_NEWNS) failed: %m\n");
      45  #endif /* CLONE_NEWNS */
      46    return false;
      47  }