eCryptfs: Handle unrecognized tag 3 cipher codes

Returns an error when an unrecognized cipher code is present in a tag 3
packet or an ecryptfs_crypt_stat cannot be initialized.  Also sets an
crypt_stat->tfm error pointer to NULL to ensure that it will not be
incorrectly freed in ecryptfs_destroy_crypt_stat().

Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: ecryptfs-devel@lists.launchpad.net
Cc: stable <stable@kernel.org>
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

fs/ecryptfs/crypto.c

@@ -795,6 +795,7 @@ int ecryptfs_init_crypt_ctx(struct ecryptfs_crypt_stat *crypt_stat)
 	kfree(full_alg_name);
 	if (IS_ERR(crypt_stat->tfm)) {
 		rc = PTR_ERR(crypt_stat->tfm);
+		crypt_stat->tfm = NULL;
 		ecryptfs_printk(KERN_ERR, "cryptfs: init_crypt_ctx(): "
 				"Error initializing cipher [%s]\n",
 				crypt_stat->cipher);

fs/ecryptfs/keystore.c

@@ -1316,8 +1316,10 @@ parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat,
 		rc = -EINVAL;
 		goto out_free;
 	}
-	ecryptfs_cipher_code_to_string(crypt_stat->cipher,
-				       (u16)data[(*packet_size)]);
+	rc = ecryptfs_cipher_code_to_string(crypt_stat->cipher,
+					    (u16)data[(*packet_size)]);
+	if (rc)
+		goto out_free;
 	/* A little extra work to differentiate among the AES key
 	 * sizes; see RFC2440 */
 	switch(data[(*packet_size)++]) {
@@ -1328,7 +1330,9 @@ parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat,
 		crypt_stat->key_size =
 			(*new_auth_tok)->session_key.encrypted_key_size;
 	}
-	ecryptfs_init_crypt_ctx(crypt_stat);
+	rc = ecryptfs_init_crypt_ctx(crypt_stat);
+	if (rc)
+		goto out_free;
 	if (unlikely(data[(*packet_size)++] != 0x03)) {
 		printk(KERN_WARNING "Only S2K ID 3 is currently supported\n");
 		rc = -ENOSYS;