Re: [PATCH v7 06/16] fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl

["Theodore Y. Ts'o" <tytso@mit.edu>]

On Fri, Jul 26, 2019 at 03:41:31PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Add a new fscrypt ioctl, FS_IOC_ADD_ENCRYPTION_KEY.  This ioctl adds an
> encryption key to the filesystem's fscrypt keyring ->s_master_keys,
> making any files encrypted with that key appear "unlocked".

Note: it think it's going to be useful to make the keyring id
available someplace like /sys/fs/<fs>/<blkdev>/keyring, or preferably
in the new fsinfo system call.  Yes, the system administrator can paw
through /proc/keys and try to figure it out, but it will be nicer if
there's a direct way to do that.

For that matter, we could just add a new ioctl which returns the file
system's keyring id.  That way an application program won't have to
try to figure out what a file's underlying sb->s_id happens to be.
(Especially if things like overlayfs are involved.)

> diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
> index 29a945d165def..93d6eabaa7de4 100644
> --- a/include/uapi/linux/fscrypt.h
> +++ b/include/uapi/linux/fscrypt.h
> +
> +struct fscrypt_key_specifier {
> +#define FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR	1
> +	__u32 type;
> +	__u32 __reserved;

Can you move the definition of FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR
outside of the structure definition, and then add a comment about what
is a "descriptor" key spec?  (And then in a later patch, please add a
comment about what is an "identifier" key type.)  There's an
explanation in Documentation/filesystems/fscrypt.rst, I know, but a
one or two line comment plus a pointer to
Documentation/filesystems/fscrypt.rst in the header file would be
really helpful.

Otherwise, it looks good.   Feel free to add:

Reviewed-by: Theodore Ts'o <tytso@mit.edu>

						- Ted