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fs-verity: add data verification hooks for ->readpages()

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Add functions that verify data pages that have been read from a
fs-verity file, against that file's Merkle tree.  These will be called
from filesystems' ->readpage() and ->readpages() methods.

Since data verification can block, a workqueue is provided for these
methods to enqueue verification work from their bio completion callback.

See the "Verifying data" section of
Documentation/filesystems/fsverity.rst for more information.

Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers 2019-07-22 09:26:22 -07:00
parent c1d9b584e2
commit 8a1d0f9cac
6 changed files with 352 additions and 1 deletions
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56
include/linux/fsverity.h
View file

@ -33,6 +33,23 @@ struct fsverity_operations {
*/
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);
};
#ifdef CONFIG_FS_VERITY
@ -49,6 +66,12 @@ 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)
@ -73,6 +96,39 @@ 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 */