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, 211 insertions, 0 deletions

diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
new file mode 100644
index 000000000000..3b6b8ccebe7d
--- /dev/null
+++ b/include/linux/fsverity.h
@@ -0,0 +1,211 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * fs-verity: read-only file-based authenticity protection
+ *
+ * This header declares the interface between the fs/verity/ support layer and
+ * filesystems that support fs-verity.
+ *
+ * Copyright 2019 Google LLC
+ */
+
+#ifndef _LINUX_FSVERITY_H
+#define _LINUX_FSVERITY_H
+
+#include <linux/fs.h>
+#include <uapi/linux/fsverity.h>
+
+/* Verity operations for filesystems */
+struct fsverity_operations {
+
+	/**
+	 * Begin enabling verity on the given file.
+	 *
+	 * @filp: a readonly file descriptor for the file
+	 *
+	 * The filesystem must do any needed filesystem-specific preparations
+	 * for enabling verity, e.g. evicting inline data.  It also must return
+	 * -EBUSY if verity is already being enabled on the given file.
+	 *
+	 * i_rwsem is held for write.
+	 *
+	 * Return: 0 on success, -errno on failure
+	 */
+	int (*begin_enable_verity)(struct file *filp);
+
+	/**
+	 * End enabling verity on the given file.
+	 *
+	 * @filp: a readonly file descriptor for the file
+	 * @desc: the verity descriptor to write, or NULL on failure
+	 * @desc_size: size of verity descriptor, or 0 on failure
+	 * @merkle_tree_size: total bytes the Merkle tree took up
+	 *
+	 * If desc == NULL, then enabling verity failed and the filesystem only
+	 * must do any necessary cleanups.  Else, it must also store the given
+	 * verity descriptor to a fs-specific location associated with the inode
+	 * and do any fs-specific actions needed to mark the inode as a verity
+	 * inode, e.g. setting a bit in the on-disk inode.  The filesystem is
+	 * also responsible for setting the S_VERITY flag in the VFS inode.
+	 *
+	 * i_rwsem is held for write, but it may have been dropped between
+	 * ->begin_enable_verity() and ->end_enable_verity().
+	 *
+	 * Return: 0 on success, -errno on failure
+	 */
+	int (*end_enable_verity)(struct file *filp, const void *desc,
+				 size_t desc_size, u64 merkle_tree_size);
+
+	/**
+	 * Get the verity descriptor of the given inode.
+	 *
+	 * @inode: an inode with the S_VERITY flag set
+	 * @buf: buffer in which to place the verity descriptor
+	 * @bufsize: size of @buf, or 0 to retrieve the size only
+	 *
+	 * If bufsize == 0, then the size of the verity descriptor is returned.
+	 * Otherwise the verity descriptor is written to 'buf' and its actual
+	 * size is returned; -ERANGE is returned if it's too large.  This may be
+	 * called by multiple processes concurrently on the same inode.
+	 *
+	 * Return: the size on success, -errno on failure
+	 */
+	int (*get_verity_descriptor)(struct inode *inode, void *buf,
+				     size_t bufsize);
+
+	/**
+	 * Read a Merkle tree page of the given inode.
+	 *
+	 * @inode: the inode
+	 * @index: 0-based index of the page within the Merkle tree
+	 *
+	 * This can be called at any time on an open verity file, as well as
+	 * between ->begin_enable_verity() and ->end_enable_verity().  It may be
+	 * called by multiple processes concurrently, even with the same page.
+	 *
+	 * Note that this must retrieve a *page*, not necessarily a *block*.
+	 *
+	 * Return: the page on success, ERR_PTR() on failure
+	 */
+	struct page *(*read_merkle_tree_page)(struct inode *inode,
+					      pgoff_t index);
+
+	/**
+	 * Write a Merkle tree block to the given inode.
+	 *
+	 * @inode: the inode for which the Merkle tree is being built
+	 * @buf: block to write
+	 * @index: 0-based index of the block within the Merkle tree
+	 * @log_blocksize: log base 2 of the Merkle tree block size
+	 *
+	 * This is only called between ->begin_enable_verity() and
+	 * ->end_enable_verity().
+	 *
+	 * Return: 0 on success, -errno on failure
+	 */
+	int (*write_merkle_tree_block)(struct inode *inode, const void *buf,
+				       u64 index, int log_blocksize);
+};
+
+#ifdef CONFIG_FS_VERITY
+
+static inline struct fsverity_info *fsverity_get_info(const struct inode *inode)
+{
+	/* pairs with the cmpxchg() in fsverity_set_info() */
+	return READ_ONCE(inode->i_verity_info);
+}
+
+/* enable.c */
+
+extern int fsverity_ioctl_enable(struct file *filp, const void __user *arg);
+
+/* measure.c */
+
+extern int fsverity_ioctl_measure(struct file *filp, void __user *arg);
+
+/* open.c */
+
+extern int fsverity_file_open(struct inode *inode, struct file *filp);
+extern int fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr);
+extern void fsverity_cleanup_inode(struct inode *inode);
+
+/* verify.c */
+
+extern bool fsverity_verify_page(struct page *page);
+extern void fsverity_verify_bio(struct bio *bio);
+extern void fsverity_enqueue_verify_work(struct work_struct *work);
+
+#else /* !CONFIG_FS_VERITY */
+
+static inline struct fsverity_info *fsverity_get_info(const struct inode *inode)
+{
+	return NULL;
+}
+
+/* enable.c */
+
+static inline int fsverity_ioctl_enable(struct file *filp,
+					const void __user *arg)
+{
+	return -EOPNOTSUPP;
+}
+
+/* measure.c */
+
+static inline int fsverity_ioctl_measure(struct file *filp, void __user *arg)
+{
+	return -EOPNOTSUPP;
+}
+
+/* open.c */
+
+static inline int fsverity_file_open(struct inode *inode, struct file *filp)
+{
+	return IS_VERITY(inode) ? -EOPNOTSUPP : 0;
+}
+
+static inline int fsverity_prepare_setattr(struct dentry *dentry,
+					   struct iattr *attr)
+{
+	return IS_VERITY(d_inode(dentry)) ? -EOPNOTSUPP : 0;
+}
+
+static inline void fsverity_cleanup_inode(struct inode *inode)
+{
+}
+
+/* verify.c */
+
+static inline bool fsverity_verify_page(struct page *page)
+{
+	WARN_ON(1);
+	return false;
+}
+
+static inline void fsverity_verify_bio(struct bio *bio)
+{
+	WARN_ON(1);
+}
+
+static inline void fsverity_enqueue_verify_work(struct work_struct *work)
+{
+	WARN_ON(1);
+}
+
+#endif	/* !CONFIG_FS_VERITY */
+
+/**
+ * fsverity_active() - do reads from the inode need to go through fs-verity?
+ *
+ * This checks whether ->i_verity_info has been set.
+ *
+ * Filesystems call this from ->readpages() to check whether the pages need to
+ * be verified or not.  Don't use IS_VERITY() for this purpose; it's subject to
+ * a race condition where the file is being read concurrently with
+ * FS_IOC_ENABLE_VERITY completing.  (S_VERITY is set before ->i_verity_info.)
+ */
+static inline bool fsverity_active(const struct inode *inode)
+{
+	return fsverity_get_info(inode) != NULL;
+}
+
+#endif	/* _LINUX_FSVERITY_H */