Re: [PATCH v8 06/12] nfit/libnvdimm: add set passphrase support for Intel nvdimms

[David Howells <dhowells@redhat.com>]

Dave Jiang <dave.jiang@intel.com> wrote:

> +	new_key = key_alloc(&key_type_logon, key->description,
> +			GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, &init_cred, 0,

KEY_POS_SEARCH?  KEY_USR_VIEW?

> +			KEY_ALLOC_NOT_IN_QUOTA, NULL);
> + ...
> +	down_read(&key->sem);
> +	payload = key->payload.data[0];
> +	rc = key_instantiate_and_link(new_key, payload->data, key->datalen,

payload->datalen, not key->datalen.

> +			nvdimm_keyring, NULL);

Okay, that's a weird way of going about things.  I presume you don't want to
add key to nvdimm_keyring - maybe in case it gets updated whilst you're using
it and your private key isn't in quota?

> +	up_read(&key->sem);
> +	if (rc < 0) {
> +		key_revoke(new_key);
> +		key_put(new_key);
> +		return NULL;
> +	}

Just putting it here should work since it didn't get linked to the keyring if
any errors occurred.  Revoking it too shouldn't be necessary.

> +	key_invalidate(key);
> +	key_put(key);

Why are you invalidating the user's key?

> +	keyref = lookup_user_key(id, 0, 0);

KEY_NEED_SEARCH?  Though I suppose it's not strictly necessary as it's a key
that's private to the kernel.

> +	if (old_keyid != 0) {
> +		old_key = nvdimm_get_key(dev);
> +		if (old_key) {
> +			if (key_serial(old_key) != old_keyid) {

Ummm...  That's not what I meant.  Given the permissions you've set on your
private key, userspace shouldn't be able to find it, let alone give you the
key ID.

What I meant here was to use, say, nvdimm_lookup_user_key() to get a key from
userspace that contains the old password.  You can use the description of the
key to search nvdimm_keyring for the private key and then compare the
passwords.

Then you don't need to passphrases in the new key.

> +	rc = nvdimm_check_key_len(key->datalen, update);

payload->datalen.

> +	down_read(&key->sem);

This needs to be earlier.  The payload attached to the new key can be replaced
by keyctl_update() at any time whilst you're not holding the lock, so you
cannot use key->payload[*] without holding the lock or the RCU read lock.

> +	if (update)
> +		key_invalidate(key);

The key doesn't belong to you - should you really be invalidating it?

> +	else {
> +		key_link(nvdimm_keyring, key);
> +		nvdimm->key = key;
> +		key->perm |= KEY_USR_SEARCH;
> +	}

Um - do you really want to be taking the key into your internal keyring?  Why
aren't you calling nvdimm_replace_key()?  Also, you shouldn't alter the
permission - it's not your key.

> +static int __parse_update(const char *buf, size_t len, unsigned int *old_id,
> +		unsigned int *new_id)
> +{

Try using sscanf()?

David
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