ntfs3: add legacy ntfs file operations

To ensure that ioctl()s can't be used to circumvent write restrictions.
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/ntfs3/dir.c

@@ -616,4 +616,11 @@ const struct file_operations ntfs_dir_operations = {
 	.compat_ioctl   = ntfs_compat_ioctl,
 #endif
 };
+
+const struct file_operations ntfs_legacy_dir_operations = {
+	.llseek		= generic_file_llseek,
+	.read		= generic_read_dir,
+	.iterate_shared	= ntfs_readdir,
+	.open		= ntfs_file_open,
+};
 // clang-format on

fs/ntfs3/file.c

@@ -1236,4 +1236,12 @@ const struct file_operations ntfs_file_operations = {
 	.fallocate	= ntfs_fallocate,
 	.release	= ntfs_file_release,
 };
+
+const struct file_operations ntfs_legacy_file_operations = {
+	.llseek		= generic_file_llseek,
+	.read_iter	= ntfs_file_read_iter,
+	.splice_read	= ntfs_file_splice_read,
+	.open		= ntfs_file_open,
+	.release	= ntfs_file_release,
+};
 // clang-format on

fs/ntfs3/inode.c

@@ -440,7 +440,10 @@ static struct inode *ntfs_read_mft(struct inode *inode,
 		 * Usually a hard links to directories are disabled.
 		 */
 		inode->i_op = &ntfs_dir_inode_operations;
-		inode->i_fop = &ntfs_dir_operations;
+		if (is_legacy_ntfs(inode->i_sb))
+			inode->i_fop = &ntfs_legacy_dir_operations;
+		else
+			inode->i_fop = &ntfs_dir_operations;
 		ni->i_valid = 0;
 	} else if (S_ISLNK(mode)) {
 		ni->std_fa &= ~FILE_ATTRIBUTE_DIRECTORY;
@@ -450,7 +453,10 @@ static struct inode *ntfs_read_mft(struct inode *inode,
 	} else if (S_ISREG(mode)) {
 		ni->std_fa &= ~FILE_ATTRIBUTE_DIRECTORY;
 		inode->i_op = &ntfs_file_inode_operations;
-		inode->i_fop = &ntfs_file_operations;
+		if (is_legacy_ntfs(inode->i_sb))
+			inode->i_fop = &ntfs_legacy_file_operations;
+		else
+			inode->i_fop = &ntfs_file_operations;
 		inode->i_mapping->a_ops = is_compressed(ni) ? &ntfs_aops_cmpr :
 							      &ntfs_aops;
 		if (ino != MFT_REC_MFT)
@@ -1614,7 +1620,10 @@ struct inode *ntfs_create_inode(struct mnt_idmap *idmap, struct inode *dir,
 
 	if (S_ISDIR(mode)) {
 		inode->i_op = &ntfs_dir_inode_operations;
-		inode->i_fop = &ntfs_dir_operations;
+		if (is_legacy_ntfs(inode->i_sb))
+			inode->i_fop = &ntfs_legacy_dir_operations;
+		else
+			inode->i_fop = &ntfs_dir_operations;
 	} else if (S_ISLNK(mode)) {
 		inode->i_op = &ntfs_link_inode_operations;
 		inode->i_fop = NULL;
@@ -1623,7 +1632,10 @@ struct inode *ntfs_create_inode(struct mnt_idmap *idmap, struct inode *dir,
 		inode_nohighmem(inode);
 	} else if (S_ISREG(mode)) {
 		inode->i_op = &ntfs_file_inode_operations;
-		inode->i_fop = &ntfs_file_operations;
+		if (is_legacy_ntfs(inode->i_sb))
+			inode->i_fop = &ntfs_legacy_file_operations;
+		else
+			inode->i_fop = &ntfs_file_operations;
 		inode->i_mapping->a_ops = is_compressed(ni) ? &ntfs_aops_cmpr :
 							      &ntfs_aops;
 		init_rwsem(&ni->file.run_lock);

fs/ntfs3/ntfs_fs.h

@@ -493,6 +493,7 @@ struct inode *dir_search_u(struct inode *dir, const struct cpu_str *uni,
 			   struct ntfs_fnd *fnd);
 bool dir_is_empty(struct inode *dir);
 extern const struct file_operations ntfs_dir_operations;
+extern const struct file_operations ntfs_legacy_dir_operations;
 
 /* Globals from file.c */
 int ntfs_getattr(struct mnt_idmap *idmap, const struct path *path,
@@ -507,6 +508,7 @@ long ntfs_compat_ioctl(struct file *filp, u32 cmd, unsigned long arg);
 extern const struct inode_operations ntfs_special_inode_operations;
 extern const struct inode_operations ntfs_file_inode_operations;
 extern const struct file_operations ntfs_file_operations;
+extern const struct file_operations ntfs_legacy_file_operations;
 
 /* Globals from frecord.c */
 void ni_remove_mi(struct ntfs_inode *ni, struct mft_inode *mi);