[PATCH 00/21] mount: more bugfixes, trapped in the Black Lodge edition

[Christian Brauner <brauner@kernel.org>]

More bugfixes from work in this area:

- unhash a dentry before detaching the mounts on it to avoid leaking
  sensitive data
- don't reveal overmounted entries in refwalk
- refuse F_SET_RW_HINT on an immutable inode
- refuse an automount below a mount that is in no namespace
- handle mount locking for automounts correctly
- don't update the access time on nullfs
- never expire a locked mount
- keep the lock on a mount that a propagated copy is moved beneath
- decide the subtree check under mount_lock
- keep the private nullfs instance in knullfs
- nothing is mounted on or written through knullfs
- let a filesystem refuse fsnotify marks on its objects
- refuse file locks on nullfs
- refuse leases and delegations on nullfs
- take no inode lock on an immutable directory

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
Christian Brauner (21):
      namespace: unhash a dentry before detaching the mounts on it
      namei: don't reveal overmounted entries in refwalk
      fcntl: refuse F_SET_RW_HINT on an immutable inode
      selftests/filesystems: check that an immutable inode takes no write hint
      namespace: refuse an automount below a mount that is in no namespace
      namespace: handle mount locking for automounts correctly
      nullfs: don't update the access time
      namespace: never expire a locked mount
      namespace: keep the lock on a mount that a propagated copy is moved beneath
      selftests/filesystems: check that a lock lands on the right mount and stays
      selftests/filesystems: check the atime of the empty mount namespace root
      selftests/filesystems: check that an automount below an overlay layer is refused
      fhandle: decide the subtree check under mount_lock
      namespace: keep the private nullfs instance in knullfs
      namespace: nothing is mounted on or written through knullfs
      fsnotify: let a filesystem refuse marks on its objects
      nullfs: refuse file locks
      nullfs: refuse leases and delegations
      readdir: take no inode lock on an immutable directory
      selftests/filesystems: add a helper that holds a readdir in a page fault
      selftests/filesystems: check that reading the root of an empty mount namespace stalls nobody

 fs/fcntl.c                                         |   3 +
 fs/fhandle.c                                       |  20 +-
 fs/mount.h                                         |   1 +
 fs/namei.c                                         |  29 ++
 fs/namespace.c                                     |  78 ++--
 fs/notify/mark.c                                   |   4 +
 fs/nullfs.c                                        |  43 +-
 fs/readdir.c                                       |  13 +-
 include/linux/fs.h                                 |   3 +
 tools/testing/selftests/filesystems/.gitignore     |   1 +
 tools/testing/selftests/filesystems/Makefile       |   2 +-
 .../selftests/filesystems/empty_mntns/.gitignore   |   2 +
 .../selftests/filesystems/empty_mntns/Makefile     |   5 +-
 .../filesystems/empty_mntns/nullfs_atime_test.c    | 129 ++++++
 .../filesystems/empty_mntns/root_readdir_test.c    |  45 +++
 .../selftests/filesystems/overlayfs/.gitignore     |   1 +
 .../selftests/filesystems/overlayfs/Makefile       |   1 +
 .../filesystems/overlayfs/automount_in_layer.c     | 174 +++++++++
 tools/testing/selftests/filesystems/readdir_hold.h | 224 +++++++++++
 tools/testing/selftests/filesystems/rw_hint_test.c | 129 ++++++
 .../filesystems/umount_propagation/Makefile        |   2 +-
 .../umount_propagation/locked_mount_test.c         | 432 +++++++++++++++++++++
 22 files changed, 1305 insertions(+), 36 deletions(-)
---
base-commit: cbade031e2ebb3ca0a423b1804ce87908b27c229
change-id: 20261002-work-mount-fixes-4-b28d7d43102e