Pull fuse updates from Miklos Szeredi:

 - Continue separating the transport (user/kernel communication) and the
   filesystem layers of fuse. Getting rid of most layering violations
   will allow for easier cleanup and optimization later on.

 - Prepare for the addition of the virtio-fs filesystem. The actual
   filesystem will be introduced by a separate pull request.

 - Convert to new mount API.

 - Various fixes, optimizations and cleanups.

* tag 'fuse-update-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse: (55 commits)
  fuse: Make fuse_args_to_req static
  fuse: fix memleak in cuse_channel_open
  fuse: fix beyond-end-of-page access in fuse_parse_cache()
  fuse: unexport fuse_put_request
  fuse: kmemcg account fs data
  fuse: on 64-bit store time in d_fsdata directly
  fuse: fix missing unlock_page in fuse_writepage()
  fuse: reserve byteswapped init opcodes
  fuse: allow skipping control interface and forced unmount
  fuse: dissociate DESTROY from fuseblk
  fuse: delete dentry if timeout is zero
  fuse: separate fuse device allocation and installation in fuse_conn
  fuse: add fuse_iqueue_ops callbacks
  fuse: extract fuse_fill_super_common()
  fuse: export fuse_dequeue_forget() function
  fuse: export fuse_get_unique()
  fuse: export fuse_send_init_request()
  fuse: export fuse_len_args()
  fuse: export fuse_end_request()
  fuse: fix request limit
  ...

Pull misc mount API conversions from Al Viro:
 "Conversions to new API for shmem and friends and for mount_mtd()-using
  filesystems.

  As for the rest of the mount API conversions in -next, some of them
  belong in the individual trees (e.g. binderfs one should definitely go
  through android folks, after getting redone on top of their changes).
  I'm going to drop those and send the rest (trivial ones + stuff ACKed
  by maintainers) in a separate series - by that point they are
  independent from each other.

  Some stuff has already migrated into individual trees (NFS conversion,
  for example, or FUSE stuff, etc.); those presumably will go through
  the regular merges from corresponding trees."

* 'work.mount2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  vfs: Make fs_parse() handle fs_param_is_fd-type params better
  vfs: Convert ramfs, shmem, tmpfs, devtmpfs, rootfs to use the new mount API
  shmem_parse_one(): switch to use of fs_parse()
  shmem_parse_options(): take handling a single option into a helper
  shmem_parse_options(): don't bother with mpol in separate variable
  shmem_parse_options(): use a separate structure to keep the results
  make shmem_fill_super() static
  make ramfs_fill_super() static
  devtmpfs: don't mix {ramfs,shmem}_fill_super() with mount_single()
  vfs: Convert squashfs to use the new mount API
  mtd: Kill mount_mtd()
  vfs: Convert jffs2 to use the new mount API
  vfs: Convert cramfs to use the new mount API
  vfs: Convert romfs to use the new mount API
  vfs: Add a single-or-reconfig keying to vfs_get_super()

Pull y2038 vfs updates from Arnd Bergmann:
 "Add inode timestamp clamping.

  This series from Deepa Dinamani adds a per-superblock minimum/maximum
  timestamp limit for a file system, and clamps timestamps as they are
  written, to avoid random behavior from integer overflow as well as
  having different time stamps on disk vs in memory.

  At mount time, a warning is now printed for any file system that can
  represent current timestamps but not future timestamps more than 30
  years into the future, similar to the arbitrary 30 year limit that was
  added to settimeofday().

  This was picked as a compromise to warn users to migrate to other file
  systems (e.g. ext4 instead of ext3) when they need the file system to
  survive beyond 2038 (or similar limits in other file systems), but not
  get in the way of normal usage"

* tag 'y2038-vfs' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground:
  ext4: Reduce ext4 timestamp warnings
  isofs: Initialize filesystem timestamp ranges
  pstore: fs superblock limits
  fs: omfs: Initialize filesystem timestamp ranges
  fs: hpfs: Initialize filesystem timestamp ranges
  fs: ceph: Initialize filesystem timestamp ranges
  fs: sysv: Initialize filesystem timestamp ranges
  fs: affs: Initialize filesystem timestamp ranges
  fs: fat: Initialize filesystem timestamp ranges
  fs: cifs: Initialize filesystem timestamp ranges
  fs: nfs: Initialize filesystem timestamp ranges
  ext4: Initialize timestamps limits
  9p: Fill min and max timestamps in sb
  fs: Fill in max and min timestamps in superblock
  utimes: Clamp the timestamps before update
  mount: Add mount warning for impending timestamp expiry
  timestamp_truncate: Replace users of timespec64_trunc
  vfs: Add timestamp_truncate() api
  vfs: Add file timestamp range support

Pull fscrypt updates from Eric Biggers:
 "This is a large update to fs/crypto/ which includes:

   - Add ioctls that add/remove encryption keys to/from a
     filesystem-level keyring.

     These fix user-reported issues where e.g. an encrypted home
     directory can break NetworkManager, sshd, Docker, etc. because they
     don't get access to the needed keyring. These ioctls also provide a
     way to lock encrypted directories that doesn't use the
     vm.drop_caches sysctl, so is faster, more reliable, and doesn't
     always need root.

   - Add a new encryption policy version ("v2") which switches to a more
     standard, secure, and flexible key derivation function, and starts
     verifying that the correct key was supplied before using it.

     The key derivation improvement is needed for its own sake as well
     as for ongoing feature work for which the current way is too
     inflexible.

  Work is in progress to update both Android and the 'fscrypt' userspace
  tool to use both these features. (Working patches are available and
  just need to be reviewed+merged.) Chrome OS will likely use them too.

  This has also been tested on ext4, f2fs, and ubifs with xfstests --
  both the existing encryption tests, and the new tests for this. This
  has also been in linux-next since Aug 16 with no reported issues. I'm
  also using an fscrypt v2-encrypted home directory on my personal
  desktop"

* tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt: (27 commits)
  ext4 crypto: fix to check feature status before get policy
  fscrypt: document the new ioctls and policy version
  ubifs: wire up new fscrypt ioctls
  f2fs: wire up new fscrypt ioctls
  ext4: wire up new fscrypt ioctls
  fscrypt: require that key be added when setting a v2 encryption policy
  fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS ioctl
  fscrypt: allow unprivileged users to add/remove keys for v2 policies
  fscrypt: v2 encryption policy support
  fscrypt: add an HKDF-SHA512 implementation
  fscrypt: add FS_IOC_GET_ENCRYPTION_KEY_STATUS ioctl
  fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl
  fscrypt: rename keyinfo.c to keysetup.c
  fscrypt: move v1 policy key setup to keysetup_v1.c
  fscrypt: refactor key setup code in preparation for v2 policies
  fscrypt: rename fscrypt_master_key to fscrypt_direct_key
  fscrypt: add ->ci_inode to fscrypt_info
  fscrypt: use FSCRYPT_* definitions, not FS_*
  fscrypt: use FSCRYPT_ prefix for uapi constants
  ...

The unused vfs code can be removed.  Don't pass empty subtype (same as if
->parse callback isn't called).

The bits that are left involve determining whether it's permitted to split the
filesystem type string passed in to mount(2).  Consequently, this means that we
cannot get rid of the FS_HAS_SUBTYPE flag unless we define that a type string
with a dot in it always indicates a subtype specification.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Add an additional keying mode to vfs_get_super() to indicate that only a
single superblock should exist in the system, and that, if it does, further
mounts should invoke reconfiguration upon it.

This allows mount_single() to be replaced.

[Fix by Eric Biggers folded in]

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Create a function, get_tree_bdev(), that is fs_context-aware and a
->get_tree() counterpart of mount_bdev().

It caches the block device pointer in the fs_context struct so that this
information can be passed into sget_fc()'s test and set functions.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: linux-block@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

For vfs_get_keyed_super users.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Add fields to the superblock to track the min and max
timestamps supported by filesystems.

Initially, when a superblock is allocated, initialize
it to the max and min values the fields can hold.
Individual filesystems override these to match their
actual limits.

Pseudo filesystems are assumed to always support the
min and max allowable values for the fields.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Acked-by: Jeff Layton <jlayton@kernel.org>

Add a new fscrypt ioctl, FS_IOC_ADD_ENCRYPTION_KEY.  This ioctl adds an
encryption key to the filesystem's fscrypt keyring ->s_master_keys,
making any files encrypted with that key appear "unlocked".

Why we need this
~~~~~~~~~~~~~~~~

The main problem is that the "locked/unlocked" (ciphertext/plaintext)
status of encrypted files is global, but the fscrypt keys are not.
fscrypt only looks for keys in the keyring(s) the process accessing the
filesystem is subscribed to: the thread keyring, process keyring, and
session keyring, where the session keyring may contain the user keyring.

Therefore, userspace has to put fscrypt keys in the keyrings for
individual users or sessions.  But this means that when a process with a
different keyring tries to access encrypted files, whether they appear
"unlocked" or not is nondeterministic.  This is because it depends on
whether the files are currently present in the inode cache.

Fixing this by consistently providing each process its own view of the
filesystem depending on whether it has the key or not isn't feasible due
to how the VFS caches work.  Furthermore, while sometimes users expect
this behavior, it is misguided for two reasons.  First, it would be an
OS-level access control mechanism largely redundant with existing access
control mechanisms such as UNIX file permissions, ACLs, LSMs, etc.
Encryption is actually for protecting the data at rest.

Second, almost all users of fscrypt actually do need the keys to be
global.  The largest users of fscrypt, Android and Chromium OS, achieve
this by having PID 1 create a "session keyring" that is inherited by
every process.  This works, but it isn't scalable because it prevents
session keyrings from being used for any other purpose.

On general-purpose Linux distros, the 'fscrypt' userspace tool [1] can't
similarly abuse the session keyring, so to make 'sudo' work on all
systems it has to link all the user keyrings into root's user keyring
[2].  This is ugly and raises security concerns.  Moreover it can't make
the keys available to system services, such as sshd trying to access the
user's '~/.ssh' directory (see [3], [4]) or NetworkManager trying to
read certificates from the user's home directory (see [5]); or to Docker
containers (see [6], [7]).

By having an API to add a key to the *filesystem* we'll be able to fix
the above bugs, remove userspace workarounds, and clearly express the
intended semantics: the locked/unlocked status of an encrypted directory
is global, and encryption is orthogonal to OS-level access control.

Why not use the add_key() syscall
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We use an ioctl for this API rather than the existing add_key() system
call because the ioctl gives us the flexibility needed to implement
fscrypt-specific semantics that will be introduced in later patches:

- Supporting key removal with the semantics such that the secret is
  removed immediately and any unused inodes using the key are evicted;
  also, the eviction of any in-use inodes can be retried.

- Calculating a key-dependent cryptographic identifier and returning it
  to userspace.

- Allowing keys to be added and removed by non-root users, but only keys
  for v2 encryption policies; and to prevent denial-of-service attacks,
  users can only remove keys they themselves have added, and a key is
  only really removed after all users who added it have removed it.

Trying to shoehorn these semantics into the keyrings syscalls would be
very difficult, whereas the ioctls make things much easier.

However, to reuse code the implementation still uses the keyrings
service internally.  Thus we get lockless RCU-mode key lookups without
having to re-implement it, and the keys automatically show up in
/proc/keys for debugging purposes.

References:

    [1] https://github.com/google/fscrypt
    [2] https://goo.gl/55cCrI#heading=h.vf09isp98isb
    [3] https://github.com/google/fscrypt/issues/111#issuecomment-444347939
    [4] https://github.com/google/fscrypt/issues/116
    [5] https://bugs.launchpad.net/ubuntu/+source/fscrypt/+bug/1770715
    [6] https://github.com/google/fscrypt/issues/128
    [7] https://askubuntu.com/questions/1130306/cannot-run-docker-on-an-encrypted-filesystem

Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>