[PATCH 00/17] mount: more bugfixes, the Oprah edition

[Christian Brauner <brauner@kernel.org>]

Yet more bugfixes falling out of my recent work in this area:

- don't let a pseudo dentry become the root of a mount
- don't drop active namespace references that were never taken
- don't put a mountpoint on a dentry that's being removed
- detach the fsnotify connector before destroying its marks
- remove the fsnotify marks of a mount namespace in process context
- don't reconfigure internal superblocks via remount and umount
- check the mounts before reading their parents in pivot_root()
- look at the topmost mount for a mount namespace file
- keep covered mounts covered in OPEN_TREE_NAMESPACE
- check a recursive bind mount for mount namespace loops
- check a submount for references right before unmounting it
- queue a mount only once for mount notifications

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
Christian Brauner (17):
      namespace: queue a mount only once for mount notifications
      namespace: check a submount for references right before unmounting it
      selftests/filesystems: check that a busy submount survives a synchronous umount
      namespace: check a recursive bind mount for mount namespace loops
      selftests/filesystems: check that a recursive bind mount can't pin the caller's mount namespace
      namespace: keep covered mounts covered in OPEN_TREE_NAMESPACE
      selftests/filesystems: check that OPEN_TREE_NAMESPACE keeps mounts covered
      namespace: look at the topmost mount for a mount namespace file
      selftests/filesystems: check that a mount namespace file on top doesn't bury a mount
      namespace: check the mounts before reading their parents in pivot_root()
      namespace: don't reconfigure internal superblocks via remount and umount
      selftests/filesystems: check that the nullfs root can't be reconfigured
      namespace: remove the fsnotify marks of a mount namespace in process context
      fsnotify: detach the connector before destroying its marks
      dcache: don't put a mountpoint on a dentry that's being removed
      unshare: don't drop active namespace references that were never taken
      namespace: don't let a pseudo dentry become the root of a mount

 fs/dcache.c                                        |   4 +-
 fs/fs_context.c                                    |   4 +
 fs/fsopen.c                                        |   3 -
 fs/mount.h                                         |   3 +
 fs/namespace.c                                     | 133 +++++++++----
 fs/notify/mark.c                                   |  16 +-
 include/linux/nsproxy.h                            |   1 +
 kernel/fork.c                                      |   3 +-
 kernel/nsproxy.c                                   |   2 +-
 .../selftests/filesystems/empty_mntns/.gitignore   |   1 +
 .../selftests/filesystems/empty_mntns/Makefile     |   2 +
 .../empty_mntns/internal_sb_reconfigure_test.c     | 108 +++++++++++
 .../selftests/filesystems/mount_cycle/.gitignore   |   2 +
 .../selftests/filesystems/mount_cycle/Makefile     |   1 +
 .../filesystems/mount_cycle/nsfs_rbind_loop_test.c | 193 +++++++++++++++++++
 .../mount_cycle/overmount_ns_file_test.c           | 187 +++++++++++++++++++
 .../selftests/filesystems/open_tree_ns/.gitignore  |   1 +
 .../selftests/filesystems/open_tree_ns/Makefile    |   2 +-
 .../open_tree_ns/open_tree_ns_covered_test.c       | 183 ++++++++++++++++++
 .../filesystems/umount_propagation/Makefile        |   2 +-
 .../umount_propagation/shrink_submounts_test.c     | 205 +++++++++++++++++++++
 21 files changed, 1008 insertions(+), 48 deletions(-)
---
base-commit: b4698e50d4601f43d21759203be5b0b3c123e383
change-id: 20260930-work-mount-fixes-3-47562ce9b80d