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namespace: make MountFlags=shared work again

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Since commit 0722b359342d2a9f9e0d453875624387a0ba1be2, the root mountpoint is
unconditionnally turned to slave which breaks units that are using explicitly
MountFlags=shared (and no other options that would implicitly require a slave
root mountpoint).

Here is a test case:

  $ systemctl cat test-shared-mount-flag.service
  # /etc/systemd/system/test-shared-mount-flag.service
  [Service]
  Type=simple
  ExecStartPre=/usr/bin/mkdir -p /mnt/tmp
  ExecStart=/bin/sh -c "/usr/bin/mount -t tmpfs -o size=10M none /mnt/tmp && sleep infinity"
  ExecStop=-/bin/sh -c "/usr/bin/umount /mnt/tmp"
  MountFlags=shared

  $ systemctl start test-shared-mount-flag.service
  $ findmnt /mnt/tmp
  $

Mount on /mnt/tmp is not visible from the host although MountFlags=shared was
used.

This patch fixes that and turns the root mountpoint to slave when it's really
required.
This commit is contained in:
Franck Bui 2019-02-13 18:45:36 +01:00 committed by Yu Watanabe
parent ebf963c551
commit 37ed15d7ed
1 changed files with 4 additions and 1 deletions
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5
src/core/execute.c
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@ -1839,7 +1839,7 @@ static bool exec_needs_mount_namespace(
if (context->n_temporary_filesystems > 0)
return true;
if (context->mount_flags != 0)
if (!IN_SET(context->mount_flags, 0, MS_SHARED))
return true;
if (context->private_tmp && runtime && (runtime->tmp_dir || runtime->var_tmp_dir))
@ -2435,6 +2435,9 @@ static int apply_mount_namespace(
else
ns_info = (NamespaceInfo) {};
if (context->mount_flags == MS_SHARED)
log_unit_debug(u, "shared mount propagation hidden by other fs namespacing unit settings: ignoring");
r = setup_namespace(root_dir, root_image,
&ns_info, context->read_write_paths,
needs_sandboxing ? context->read_only_paths : NULL,