eCryptfs: NULL pointer dereference in ecryptfs_send_miscdev()

If data is NULL, msg_ctx->msg is set to NULL and then dereferenced
afterwards. ecryptfs_send_raw_message() is the only place that
ecryptfs_send_miscdev() is called with data being NULL, but the only
caller of that function (ecryptfs_process_helo()) is never called. In
short, there is currently no way to trigger the NULL pointer
dereference.

This patch removes the two unused functions and modifies
ecryptfs_send_miscdev() to remove the NULL dereferences.

Signed-off-by: Tyler Hicks <[e-mail]>

fs/ecryptfs/messaging.c

···
 	return rc;
 }
 
-static int
-ecryptfs_send_message_locked(char *data, int data_len, u8 msg_type,
-			     struct ecryptfs_msg_ctx **msg_ctx);
-
-/**
- * ecryptfs_send_raw_message
- * @msg_type: Message type
- * @daemon: Daemon struct for recipient of message
- *
- * A raw message is one that does not include an ecryptfs_message
- * struct. It simply has a type.
- *
- * Must be called with ecryptfs_daemon_hash_mux held.
- *
- * Returns zero on success; non-zero otherwise
- */
-static int ecryptfs_send_raw_message(u8 msg_type,
-				     struct ecryptfs_daemon *daemon)
-{
-	struct ecryptfs_msg_ctx *msg_ctx;
-	int rc;
-
-	rc = ecryptfs_send_message_locked(NULL, 0, msg_type, &msg_ctx);
-	if (rc) {
-		printk(KERN_ERR "%s: Error whilst attempting to send "
-		       "message to ecryptfsd; rc = [%d]\n", __func__, rc);
-		goto out;
-	}
-	/* Raw messages are logically context-free (e.g., no
-	 * reply is expected), so we set the state of the
-	 * ecryptfs_msg_ctx object to indicate that it should
-	 * be freed as soon as the message is sent. */
-	mutex_lock(&msg_ctx->mux);
-	msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_NO_REPLY;
-	mutex_unlock(&msg_ctx->mux);
-out:
-	return rc;
-}
-
 /**
  * ecryptfs_spawn_daemon - Create and initialize a new daemon struct
  * @daemon: Pointer to set to newly allocated daemon struct
···
 	hlist_add_head(&(*daemon)->euid_chain,
 		       &ecryptfs_daemon_hash[ecryptfs_uid_hash(euid)]);
 out:
-	return rc;
-}
-
-/**
- * ecryptfs_process_helo
- * @euid: The user ID owner of the message
- * @user_ns: The namespace in which @euid applies
- * @pid: The process ID for the userspace program that sent the
- *       message
- *
- * Adds the euid and pid values to the daemon euid hash.  If an euid
- * already has a daemon pid registered, the daemon will be
- * unregistered before the new daemon is put into the hash list.
- * Returns zero after adding a new daemon to the hash list;
- * non-zero otherwise.
- */
-int ecryptfs_process_helo(uid_t euid, struct user_namespace *user_ns,
-			  struct pid *pid)
-{
-	struct ecryptfs_daemon *new_daemon;
-	struct ecryptfs_daemon *old_daemon;
-	int rc;
-
-	mutex_lock(&ecryptfs_daemon_hash_mux);
-	rc = ecryptfs_find_daemon_by_euid(&old_daemon, euid, user_ns);
-	if (rc != 0) {
-		printk(KERN_WARNING "Received request from user [%d] "
-		       "to register daemon [0x%p]; unregistering daemon "
-		       "[0x%p]\n", euid, pid, old_daemon->pid);
-		rc = ecryptfs_send_raw_message(ECRYPTFS_MSG_QUIT, old_daemon);
-		if (rc)
-			printk(KERN_WARNING "Failed to send QUIT "
-			       "message to daemon [0x%p]; rc = [%d]\n",
-			       old_daemon->pid, rc);
-		hlist_del(&old_daemon->euid_chain);
-		kfree(old_daemon);
-	}
-	rc = ecryptfs_spawn_daemon(&new_daemon, euid, user_ns, pid);
-	if (rc)
-		printk(KERN_ERR "%s: The gods are displeased with this attempt "
-		       "to create a new daemon object for euid [%d]; pid "
-		       "[0x%p]; rc = [%d]\n", __func__, euid, pid, rc);
-	mutex_unlock(&ecryptfs_daemon_hash_mux);
 	return rc;
 }
 

fs/ecryptfs/miscdev.c

···
 	int rc = 0;
 
 	mutex_lock(&msg_ctx->mux);
-	if (data) {
-		msg_ctx->msg = kmalloc((sizeof(*msg_ctx->msg) + data_size),
-				       GFP_KERNEL);
-		if (!msg_ctx->msg) {
-			rc = -ENOMEM;
-			printk(KERN_ERR "%s: Out of memory whilst attempting "
-			       "to kmalloc(%zd, GFP_KERNEL)\n", __func__,
-			       (sizeof(*msg_ctx->msg) + data_size));
-			goto out_unlock;
-		}
-	} else
-		msg_ctx->msg = NULL;
+	msg_ctx->msg = kmalloc((sizeof(*msg_ctx->msg) + data_size),
+			       GFP_KERNEL);
+	if (!msg_ctx->msg) {
+		rc = -ENOMEM;
+		printk(KERN_ERR "%s: Out of memory whilst attempting "
+		       "to kmalloc(%zd, GFP_KERNEL)\n", __func__,
+		       (sizeof(*msg_ctx->msg) + data_size));
+		goto out_unlock;
+	}
 	msg_ctx->msg->index = msg_ctx->index;
 	msg_ctx->msg->data_len = data_size;
 	msg_ctx->type = msg_type;
-	if (data) {
-		memcpy(msg_ctx->msg->data, data, data_size);
-		msg_ctx->msg_size = (sizeof(*msg_ctx->msg) + data_size);
-	} else
-		msg_ctx->msg_size = 0;
+	memcpy(msg_ctx->msg->data, data, data_size);
+	msg_ctx->msg_size = (sizeof(*msg_ctx->msg) + data_size);
 	mutex_lock(&daemon->mux);
 	list_add_tail(&msg_ctx->daemon_out_list, &daemon->msg_ctx_out_queue);
 	daemon->num_queued_msg_ctx++;