fs/ntfs3: Fix root inode checking

Separate checking inode->i_op and inode itself.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://lore.kernel.org/r/202302162319.bDJOuyfy-lkp@intel.com/
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

Author: aalexandrovich

fs/ntfs3/super.c

@@ -1347,12 +1347,21 @@ static int ntfs_fill_super(struct super_block *sb, struct fs_context *fc)
 	ref.low = cpu_to_le32(MFT_REC_ROOT);
 	ref.seq = cpu_to_le16(MFT_REC_ROOT);
 	inode = ntfs_iget5(sb, &ref, &NAME_ROOT);
-	if (IS_ERR(inode) || !inode->i_op) {
+	if (IS_ERR(inode)) {
 		err = PTR_ERR(inode);
 		ntfs_err(sb, "Failed to load root (%d).", err);
 		goto out;
 	}
 
+	/*
+	 * Final check. Looks like this case should never occurs.
+	 */
+	if (!inode->i_op) {
+		err = -EINVAL;
+		ntfs_err(sb, "Failed to load root (%d).", err);
+		goto put_inode_out;
+	}
+
 	sb->s_root = d_make_root(inode);
 	if (!sb->s_root) {
 		err = -ENOMEM;