Commit ab508822 authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

ovl: improve mount helpers 



Move common checks into ovl_mount_dir() helper.

Create helper for looking up lower directories.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
parent 3b7a9a24

fs/overlayfs/super.c

+73 −52
Original line number Diff line number Diff line
@@ -669,24 +669,6 @@ static void ovl_unescape(char *s) 
	}

}



static int ovl_mount_dir(const char *name, struct path *path)

{

	int err;

	char *tmp = kstrdup(name, GFP_KERNEL);



	if (!tmp)

		return -ENOMEM;



	ovl_unescape(tmp);

	err = kern_path(tmp, LOOKUP_FOLLOW, path);

	if (err) {

		pr_err("overlayfs: failed to resolve '%s': %i\n", tmp, err);

		err = -EINVAL;

	}

	kfree(tmp);

	return err;

}



static bool ovl_is_allowed_fs_type(struct dentry *root)

{

	const struct dentry_operations *dop = root->d_op;
@@ -706,6 +688,71 @@ static bool ovl_is_allowed_fs_type(struct dentry *root) 
	return true;

}



static int ovl_mount_dir_noesc(const char *name, struct path *path)

{

	int err;



	err = kern_path(name, LOOKUP_FOLLOW, path);

	if (err) {

		pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);

		goto out;

	}

	err = -EINVAL;

	if (!ovl_is_allowed_fs_type(path->dentry)) {

		pr_err("overlayfs: filesystem on '%s' not supported\n", name);

		goto out_put;

	}

	if (!S_ISDIR(path->dentry->d_inode->i_mode)) {

		pr_err("overlayfs: '%s' not a directory\n", name);

		goto out_put;

	}

	return 0;



out_put:

	path_put(path);

out:

	return err;

}



static int ovl_mount_dir(const char *name, struct path *path)

{

	int err = -ENOMEM;

	char *tmp = kstrdup(name, GFP_KERNEL);



	if (tmp) {

		ovl_unescape(tmp);

		err = ovl_mount_dir_noesc(tmp, path);

		kfree(tmp);

	}

	return err;

}



static int ovl_lower_dir(const char *name, struct path *path, long *namelen,

			 int *stack_depth)

{

	int err;

	struct kstatfs statfs;



	err = ovl_mount_dir(name, path);

	if (err)

		goto out;



	err = vfs_statfs(path, &statfs);

	if (err) {

		pr_err("overlayfs: statfs failed on '%s'\n", name);

		goto out_put;

	}

	*namelen = max(*namelen, statfs.f_namelen);

	*stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);



	return 0;



out_put:

	path_put(path);

out:

	return err;

}



/* Workdir should not be subdir of upperdir and vice versa */

static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)

{
@@ -726,7 +773,6 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
	struct dentry *root_dentry;

	struct ovl_entry *oe;

	struct ovl_fs *ufs;

	struct kstatfs statfs;

	struct vfsmount *mnt;

	unsigned int i;

	int err;
@@ -756,48 +802,23 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
	if (err)

		goto out_put_upperpath;



	err = ovl_mount_dir(ufs->config.lowerdir, &lowerpath);

	if (err)

		goto out_put_workpath;



	err = -EINVAL;

	if (!S_ISDIR(upperpath.dentry->d_inode->i_mode) ||

	    !S_ISDIR(lowerpath.dentry->d_inode->i_mode) ||

	    !S_ISDIR(workpath.dentry->d_inode->i_mode)) {

		pr_err("overlayfs: upperdir or lowerdir or workdir not a directory\n");

		goto out_put_lowerpath;

	}



	if (upperpath.mnt != workpath.mnt) {

		pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");

		goto out_put_lowerpath;

		goto out_put_workpath;

	}

	if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) {

		pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");

		goto out_put_lowerpath;

	}



	if (!ovl_is_allowed_fs_type(upperpath.dentry)) {

		pr_err("overlayfs: filesystem of upperdir is not supported\n");

		goto out_put_lowerpath;

	}



	if (!ovl_is_allowed_fs_type(lowerpath.dentry)) {

		pr_err("overlayfs: filesystem of lowerdir is not supported\n");

		goto out_put_lowerpath;

	}



	err = vfs_statfs(&lowerpath, &statfs);

	if (err) {

		pr_err("overlayfs: statfs failed on lowerpath\n");

		goto out_put_lowerpath;

		goto out_put_workpath;

	}

	ufs->lower_namelen = statfs.f_namelen;

	sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;



	sb->s_stack_depth = max(upperpath.mnt->mnt_sb->s_stack_depth,

				lowerpath.mnt->mnt_sb->s_stack_depth) + 1;

	err = ovl_lower_dir(ufs->config.lowerdir, &lowerpath,

			    &ufs->lower_namelen, &sb->s_stack_depth);

	if (err)

		goto out_put_workpath;



	err = -EINVAL;

	sb->s_stack_depth++;

	if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {

		pr_err("overlayfs: maximum fs stacking depth exceeded\n");

		goto out_put_lowerpath;