Merge tag 'fsverity-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt

Pull fs-verity support from Eric Biggers:
 "fs-verity is a filesystem feature that provides Merkle tree based
  hashing (similar to dm-verity) for individual readonly files, mainly
  for the purpose of efficient authenticity verification.

  This pull request includes:

   (a) The fs/verity/ support layer and documentation.

   (b) fs-verity support for ext4 and f2fs.

  Compared to the original fs-verity patchset from last year, the UAPI
  to enable fs-verity on a file has been greatly simplified. Lots of
  other things were cleaned up too.

  fs-verity is planned to be used by two different projects on Android;
  most of the userspace code is in place already. Another userspace tool
  ("fsverity-utils"), and xfstests, are also available. e2fsprogs and
  f2fs-tools already have fs-verity support. Other people have shown
  interest in using fs-verity too.

  I've tested this on ext4 and f2fs with xfstests, both the existing
  tests and the new fs-verity tests. This has also been in linux-next
  since July 30 with no reported issues except a couple minor ones I
  found myself and folded in fixes for.

  Ted and I will be co-maintaining fs-verity"

* tag 'fsverity-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt:
  f2fs: add fs-verity support
  ext4: update on-disk format documentation for fs-verity
  ext4: add fs-verity read support
  ext4: add basic fs-verity support
  fs-verity: support builtin file signatures
  fs-verity: add SHA-512 support
  fs-verity: implement FS_IOC_MEASURE_VERITY ioctl
  fs-verity: implement FS_IOC_ENABLE_VERITY ioctl
  fs-verity: add data verification hooks for ->readpages()
  fs-verity: add the hook for file ->setattr()
  fs-verity: add the hook for file ->open()
  fs-verity: add inode and superblock fields
  fs-verity: add Kconfig and the helper functions for hashing
  fs: uapi: define verity bit for FS_IOC_GETFLAGS
  fs-verity: add UAPI header
  fs-verity: add MAINTAINERS file entry
  fs-verity: add a documentation file

1 files changed, 41 insertions, 0 deletions

diff --git a/Documentation/filesystems/ext4/verity.rst b/Documentation/filesystems/ext4/verity.rst
new file mode 100644
index 000000000000..3e4c0ee0e068
--- /dev/null
+++ b/Documentation/filesystems/ext4/verity.rst
@@ -0,0 +1,41 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Verity files
+------------
+
+ext4 supports fs-verity, which is a filesystem feature that provides
+Merkle tree based hashing for individual readonly files.  Most of
+fs-verity is common to all filesystems that support it; see
+:ref:`Documentation/filesystems/fsverity.rst <fsverity>` for the
+fs-verity documentation.  However, the on-disk layout of the verity
+metadata is filesystem-specific.  On ext4, the verity metadata is
+stored after the end of the file data itself, in the following format:
+
+- Zero-padding to the next 65536-byte boundary.  This padding need not
+  actually be allocated on-disk, i.e. it may be a hole.
+
+- The Merkle tree, as documented in
+  :ref:`Documentation/filesystems/fsverity.rst
+  <fsverity_merkle_tree>`, with the tree levels stored in order from
+  root to leaf, and the tree blocks within each level stored in their
+  natural order.
+
+- Zero-padding to the next filesystem block boundary.
+
+- The verity descriptor, as documented in
+  :ref:`Documentation/filesystems/fsverity.rst <fsverity_descriptor>`,
+  with optionally appended signature blob.
+
+- Zero-padding to the next offset that is 4 bytes before a filesystem
+  block boundary.
+
+- The size of the verity descriptor in bytes, as a 4-byte little
+  endian integer.
+
+Verity inodes have EXT4_VERITY_FL set, and they must use extents, i.e.
+EXT4_EXTENTS_FL must be set and EXT4_INLINE_DATA_FL must be clear.
+They can have EXT4_ENCRYPT_FL set, in which case the verity metadata
+is encrypted as well as the data itself.
+
+Verity files cannot have blocks allocated past the end of the verity
+metadata.