[PATCH 20/26] ubifs: Add support for encrypted symlinks

[Eric Biggers]

On Fri, Oct 21, 2016 at 02:48:35PM +0200, Richard Weinberger wrote:
> +
> +	if (!dentry)
> +		return ERR_PTR(-ECHILD);
> +
> +	if (ubifs_crypt_is_encrypted(inode)) {
> +		err = fscrypt_get_encryption_info(inode);
> +		if (err)
> +			return ERR_PTR(err);
> +	} else
> +		return ui->data;
> +

This will make path lookups drop out of RCU mode when an unencrypted symlink is
followed.  This can be avoided by checking for unencrypted symlinks first:

	if (!ubifs_crypt_is_encrypted(inode))
		return ui->data;

	if (!dentry)
		return ERR_PTR(-ECHILD);

	err = fscrypt_get_encryption_info(inode);
	if (err)
		return ERR_PTR(err);

> +
> +	pstr.name[err] = '\0';
> +

In 4.9, fscrypt_fname_{disk_to_usr,usr_to_disk} return 0 instead of the output
length, so this will need to be changed to 'pstr.name[pstr.len] = '\0''.