fs-verity: add the hook for file ->open()

Add the fsverity_file_open() function, which prepares an fs-verity file
to be read from.  If not already done, it loads the fs-verity descriptor
from the filesystem and sets up an fsverity_info structure for the inode
which describes the Merkle tree and contains the file measurement.  It
also denies all attempts to open verity files for writing.

This commit also begins the include/linux/fsverity.h header, which
declares the interface between fs/verity/ and filesystems.

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

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/verity/init.c b/fs/verity/init.c
index 40076bbe452a..fff1fd634335 100644
--- a/fs/verity/init.c
+++ b/fs/verity/init.c
@@ -33,8 +33,14 @@ void fsverity_msg(const struct inode *inode, const char *level,
 
 static int __init fsverity_init(void)
 {
+	int err;
+
 	fsverity_check_hash_algs();
 
+	err = fsverity_init_info_cache();
+	if (err)
+		return err;
+
 	pr_debug("Initialized fs-verity\n");
 	return 0;
 }