Bluetooth: RFCOMM: free the skb when the DLC has no owner

Overview

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: RFCOMM: free the skb when the DLC has no owner

rfcomm_recv_data() hands the skb to d->data_ready() and returns 0 without freeing it, so the callback owns the skb from that point on. The tty implementation frees it when the DLC has been detached from its device:

static void rfcomm_dev_data_ready(struct rfcomm_dlc *dlc, struct sk_buff *skb) { struct rfcomm_dev *dev = dlc->owner;

      if (!dev) {
              kfree_skb(skb);
              return;
      }

The socket implementation returns without freeing it, and the skb is leaked.

A connected DLC can have no owner: rfcomm_sock_destruct() clears d->owner, while the DLC itself stays on the session until it is closed. Data frames that arrive in that window still find d->state == BT_CONNECTED in rfcomm_recv_data() and are handed to the callback, one leaked skb each.

The leak does not stop on its own either. The remote runs out of credits only once RFCOMM_RX_THROTTLED is set, and for a socket the only place that sets it is rfcomm_sk_data_ready() itself, below the return. rfcomm_process_dlcs() keeps granting credits, so the remote keeps sending and the leak keeps growing.

Free the skb, as the tty side does.

Affected

• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < a54ce160e3ef7e50ec94e0ac4131c3d0f9f739b9
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < c3f76b025cbbb0ab47310dbe7de18092d89f2a99
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 4f46de658ce61968aef5ea7ae809d1c180330544
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < b8814161b14c610b7a09527433301d8ad8180aef
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 9d1afbf60ed53c5b051cd124153e0ae3078c8b93
• Linux 2.6.12

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.