ecryptfs: release keys loaded in ecryptfs_keyring_auth_tok_for_sig()

This patch allows keys requested in the function
ecryptfs_keyring_auth_tok_for_sig()to be released when they are no
longer required. In particular keys are directly released in the same
function if the obtained authentication token is not valid.

Further, a new function parameter 'auth_tok_key' has been added to
ecryptfs_find_auth_tok_for_sig() in order to provide callers the key
pointer to be passed to key_put().

Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
Cc: Dustin Kirkland <kirkland@canonical.com>
Cc: James Morris <jmorris@namei.org>
[Tyler: Initialize auth_tok_key to NULL in ecryptfs_parse_packet_set]
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

fs/ecryptfs/keystore.c

@@ -446,6 +446,7 @@ out:
  */
 static int
 ecryptfs_find_auth_tok_for_sig(
+	struct key **auth_tok_key,
 	struct ecryptfs_auth_tok **auth_tok,
 	struct ecryptfs_mount_crypt_stat *mount_crypt_stat,
 	char *sig)
@@ -453,12 +454,12 @@ ecryptfs_find_auth_tok_for_sig(
 	struct ecryptfs_global_auth_tok *global_auth_tok;
 	int rc = 0;
 
+	(*auth_tok_key) = NULL;
 	(*auth_tok) = NULL;
 	if (ecryptfs_find_global_auth_tok_for_sig(&global_auth_tok,
 						  mount_crypt_stat, sig)) {
-		struct key *auth_tok_key;
 
-		rc = ecryptfs_keyring_auth_tok_for_sig(&auth_tok_key, auth_tok,
+		rc = ecryptfs_keyring_auth_tok_for_sig(auth_tok_key, auth_tok,
 						       sig);
 	} else
 		(*auth_tok) = global_auth_tok->global_auth_tok;
@@ -509,6 +510,7 @@ ecryptfs_write_tag_70_packet(char *dest, size_t *remaining_bytes,
 			     char *filename, size_t filename_size)
 {
 	struct ecryptfs_write_tag_70_packet_silly_stack *s;
+	struct key *auth_tok_key = NULL;
 	int rc = 0;
 
 	s = kmalloc(sizeof(*s), GFP_KERNEL);
@@ -606,6 +608,7 @@ ecryptfs_write_tag_70_packet(char *dest, size_t *remaining_bytes,
 	}
 	dest[s->i++] = s->cipher_code;
 	rc = ecryptfs_find_auth_tok_for_sig(
+		&auth_tok_key,
 		&s->auth_tok, mount_crypt_stat,
 		mount_crypt_stat->global_default_fnek_sig);
 	if (rc) {
@@ -753,6 +756,8 @@ out_free_unlock:
 out_unlock:
 	mutex_unlock(s->tfm_mutex);
 out:
+	if (auth_tok_key)
+		key_put(auth_tok_key);
 	kfree(s);
 	return rc;
 }
@@ -798,6 +803,7 @@ ecryptfs_parse_tag_70_packet(char **filename, size_t *filename_size,
 			     char *data, size_t max_packet_size)
 {
 	struct ecryptfs_parse_tag_70_packet_silly_stack *s;
+	struct key *auth_tok_key = NULL;
 	int rc = 0;
 
 	(*packet_size) = 0;
@@ -910,7 +916,8 @@ ecryptfs_parse_tag_70_packet(char **filename, size_t *filename_size,
 	 * >= ECRYPTFS_MAX_IV_BYTES. */
 	memset(s->iv, 0, ECRYPTFS_MAX_IV_BYTES);
 	s->desc.info = s->iv;
-	rc = ecryptfs_find_auth_tok_for_sig(&s->auth_tok, mount_crypt_stat,
+	rc = ecryptfs_find_auth_tok_for_sig(&auth_tok_key,
+					    &s->auth_tok, mount_crypt_stat,
 					    s->fnek_sig_hex);
 	if (rc) {
 		printk(KERN_ERR "%s: Error attempting to find auth tok for "
@@ -986,6 +993,8 @@ out:
 		(*filename_size) = 0;
 		(*filename) = NULL;
 	}
+	if (auth_tok_key)
+		key_put(auth_tok_key);
 	kfree(s);
 	return rc;
 }
@@ -1557,14 +1566,19 @@ int ecryptfs_keyring_auth_tok_for_sig(struct key **auth_tok_key,
 		       ECRYPTFS_VERSION_MAJOR,
 		       ECRYPTFS_VERSION_MINOR);
 		rc = -EINVAL;
-		goto out;
+		goto out_release_key;
 	}
 	if ((*auth_tok)->token_type != ECRYPTFS_PASSWORD
 	    && (*auth_tok)->token_type != ECRYPTFS_PRIVATE_KEY) {
 		printk(KERN_ERR "Invalid auth_tok structure "
 		       "returned from key query\n");
 		rc = -EINVAL;
-		goto out;
+		goto out_release_key;
+	}
+out_release_key:
+	if (rc) {
+		key_put(*auth_tok_key);
+		(*auth_tok_key) = NULL;
 	}
 out:
 	return rc;
@@ -1688,6 +1702,7 @@ int ecryptfs_parse_packet_set(struct ecryptfs_crypt_stat *crypt_stat,
 	struct ecryptfs_auth_tok_list_item *auth_tok_list_item;
 	size_t tag_11_contents_size;
 	size_t tag_11_packet_size;
+	struct key *auth_tok_key = NULL;
 	int rc = 0;
 
 	INIT_LIST_HEAD(&auth_tok_list);
@@ -1784,6 +1799,10 @@ int ecryptfs_parse_packet_set(struct ecryptfs_crypt_stat *crypt_stat,
 	 * just one will be sufficient to decrypt to get the FEK. */
 find_next_matching_auth_tok:
 	found_auth_tok = 0;
+	if (auth_tok_key) {
+		key_put(auth_tok_key);
+		auth_tok_key = NULL;
+	}
 	list_for_each_entry(auth_tok_list_item, &auth_tok_list, list) {
 		candidate_auth_tok = &auth_tok_list_item->auth_tok;
 		if (unlikely(ecryptfs_verbosity > 0)) {
@@ -1800,7 +1819,8 @@ find_next_matching_auth_tok:
 			rc = -EINVAL;
 			goto out_wipe_list;
 		}
-		ecryptfs_find_auth_tok_for_sig(&matching_auth_tok,
+		ecryptfs_find_auth_tok_for_sig(&auth_tok_key,
+					       &matching_auth_tok,
 					       crypt_stat->mount_crypt_stat,
 					       candidate_auth_tok_sig);
 		if (matching_auth_tok) {
@@ -1866,6 +1886,8 @@ found_matching_auth_tok:
 out_wipe_list:
 	wipe_auth_tok_list(&auth_tok_list);
 out:
+	if (auth_tok_key)
+		key_put(auth_tok_key);
 	return rc;
 }