udf: avoid info leak on export

commit 0143fc5e upstream.

For type 0x51 the udf.parent_partref member in struct fid gets copied
uninitialized to userland. Fix this by initializing it to 0.
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

fs/udf/namei.c

@@ -1331,6 +1331,7 @@ static int udf_encode_fh(struct dentry *de, __u32 *fh, int *lenp,
 	*lenp = 3;
 	fid->udf.block = location.logicalBlockNum;
 	fid->udf.partref = location.partitionReferenceNum;
+	fid->udf.parent_partref = 0;
 	fid->udf.generation = inode->i_generation;
 
 	if (connectable && !S_ISDIR(inode->i_mode)) {