int b43_dma_tx(struct b43_wldev *dev, struct sk_buff *skb)
{
	struct b43_dmaring *ring;
	struct ieee80211_hdr *hdr;
	int err = 0;
	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);

	hdr = (struct ieee80211_hdr *)skb->data;
	if (info->flags & IEEE80211_TX_CTL_SEND_AFTER_DTIM) {
		/* The multicast ring will be sent after the DTIM */
		ring = dev->dma.tx_ring_mcast;
		/* Set the more-data bit. Ucode will clear it on
		 * the last frame for us. */
		hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_MOREDATA);
	} else {
		/* Decide by priority where to put this frame. */
		ring = select_ring_by_priority(
			dev, skb_get_queue_mapping(skb));
	}

	B43_WARN_ON(!ring->tx);

	if (unlikely(ring->stopped)) {
		/* We get here only because of a bug in mac80211.
		 * Because of a race, one packet may be queued after
		 * the queue is stopped, thus we got called when we shouldn't.
		 * For now, just refuse the transmit. */
		if (b43_debug(dev, B43_DBG_DMAVERBOSE))
			b43err(dev->wl, "Packet after queue stopped\n");
		err = -ENOSPC;
		goto out;
	}

	if (unlikely(WARN_ON(free_slots(ring) < TX_SLOTS_PER_FRAME))) {
		/* If we get here, we have a real error with the queue
		 * full, but queues not stopped. */
		b43err(dev->wl, "DMA queue overflow\n");
		err = -ENOSPC;
		goto out;
	}

	/* Assign the queue number to the ring (if not already done before)
	 * so TX status handling can use it. The queue to ring mapping is
	 * static, so we don't need to store it per frame. */
	ring->queue_prio = skb_get_queue_mapping(skb);

	err = dma_tx_fragment(ring, skb);
	if (unlikely(err == -ENOKEY)) {
		/* Drop this packet, as we don't have the encryption key
		 * anymore and must not transmit it unencrypted. */
		dev_kfree_skb_any(skb);
		err = 0;
		goto out;
	}
	if (unlikely(err)) {
		b43err(dev->wl, "DMA tx mapping failure\n");
		goto out;
	}
	if ((free_slots(ring) < TX_SLOTS_PER_FRAME) ||
	    should_inject_overflow(ring)) {
		/* This TX ring is full. */
		ieee80211_stop_queue(dev->wl->hw, skb_get_queue_mapping(skb));
		ring->stopped = 1;
		if (b43_debug(dev, B43_DBG_DMAVERBOSE)) {
			b43dbg(dev->wl, "Stopped TX ring %d\n", ring->index);
		}
	}
out:

	return err;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.