[git pull] several mount fixes

[Al Viro <viro@zeniv.linux.org.uk>]

More stuff caught in mount code audit.  There's more, but those'll have to
wait for several days...

A couple of races around legalize_mnt vs. umount (both fairly old and hard to
hit) plus two bugs in move_mount(2) - both around "move detached subtree in
place" logics.

The following changes since commit 92a09c47464d040866cf2b4cd052bc60555185fb:

  Linux 6.15-rc5 (2025-05-04 13:55:04 -0700)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git tags/pull-fixes

for you to fetch changes up to d1ddc6f1d9f0cf887834eb54a5a68bbfeec1bb77:

  fix IS_MNT_PROPAGATING uses (2025-05-09 18:06:27 -0400)

----------------------------------------------------------------
assorted namespace fixes

----------------------------------------------------------------
Al Viro (4):
      __legitimize_mnt(): check for MNT_SYNC_UMOUNT should be under mount_lock
      do_umount(): add missing barrier before refcount checks in sync case
      do_move_mount(): don't leak MNTNS_PROPAGATING on failures
      fix IS_MNT_PROPAGATING uses

 fs/namespace.c | 17 +++++++----------
 fs/pnode.c     | 17 +++++++++--------
 fs/pnode.h     |  2 +-
 3 files changed, 17 insertions(+), 19 deletions(-)