eCryptfs: parse_tag_3_packet check tag 3 packet encrypted key size

The parse_tag_3_packet function does not check if the tag 3 packet contains a
encrypted key size larger than ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES.

Signed-off-by: Ramon de Carvalho Valle <[e-mail]>
[[e-mail]: Added printk newline and changed goto to out_free]
Signed-off-by: Tyler Hicks <[e-mail]>
Cc: [e-mail] (2.6.27 and 30)
Signed-off-by: Linus Torvalds <[e-mail]>

fs/ecryptfs/keystore.c

···
 	}
 	(*new_auth_tok)->session_key.encrypted_key_size =
 		(body_size - (ECRYPTFS_SALT_SIZE + 5));
+	if ((*new_auth_tok)->session_key.encrypted_key_size
+	    > ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES) {
+		printk(KERN_WARNING "Tag 3 packet contains key larger "
+		       "than ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES\n");
+		rc = -EINVAL;
+		goto out_free;
+	}
 	if (unlikely(data[(*packet_size)++] != 0x04)) {
 		printk(KERN_WARNING "Unknown version number [%d]\n",
 		       data[(*packet_size) - 1]);