support/support_enter_mount_namespace.c

   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 }