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Commit f60c55a9 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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
parents 734d1ed8 95ae251f

Documentation/filesystems/ext4/inodes.rst

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@@ -277,6 +277,8 @@ The ``i_flags`` field is a combination of these values: 
     - This is a huge file (EXT4\_HUGE\_FILE\_FL).

   * - 0x80000

     - Inode uses extents (EXT4\_EXTENTS\_FL).

   * - 0x100000

     - Verity protected file (EXT4\_VERITY\_FL).

   * - 0x200000

     - Inode stores a large extended attribute value in its data blocks

       (EXT4\_EA\_INODE\_FL).
@@ -299,9 +301,9 @@ The ``i_flags`` field is a combination of these values: 
     - Reserved for ext4 library (EXT4\_RESERVED\_FL).

   * -

     - Aggregate flags:

   * - 0x4BDFFF

   * - 0x705BDFFF

     - User-visible flags.

   * - 0x4B80FF

   * - 0x604BC0FF

     - User-modifiable flags. Note that while EXT4\_JOURNAL\_DATA\_FL and

       EXT4\_EXTENTS\_FL can be set with setattr, they are not in the kernel's

       EXT4\_FL\_USER\_MODIFIABLE mask, since it needs to handle the setting of

Documentation/filesystems/ext4/overview.rst

+1 −0
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@@ -24,3 +24,4 @@ order. 
.. include:: bigalloc.rst

.. include:: inlinedata.rst

.. include:: eainode.rst

.. include:: verity.rst

Documentation/filesystems/ext4/super.rst

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@@ -696,6 +696,8 @@ the following: 
       (RO\_COMPAT\_READONLY)

   * - 0x2000

     - Filesystem tracks project quotas. (RO\_COMPAT\_PROJECT)

   * - 0x8000

     - Verity inodes may be present on the filesystem. (RO\_COMPAT\_VERITY)



.. _super_def_hash:

Documentation/filesystems/ext4/verity.rst

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.. 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.

Documentation/filesystems/fsverity.rst

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