void b43_dma_handle_txstatus(struct b43_wldev *dev,
			     const struct b43_txstatus *status)
{
	const struct b43_dma_ops *ops;
	struct b43_dmaring *ring;
	struct b43_dmadesc_generic *desc;
	struct b43_dmadesc_meta *meta;
	int slot, firstused;
	bool frame_succeed;

	ring = parse_cookie(dev, status->cookie, &slot);
	if (unlikely(!ring))
		return;
	B43_WARN_ON(!ring->tx);

	/* Sanity check: TX packets are processed in-order on one ring.
	 * Check if the slot deduced from the cookie really is the first
	 * used slot. */
	firstused = ring->current_slot - ring->used_slots + 1;
	if (firstused < 0)
		firstused = ring->nr_slots + firstused;
	if (unlikely(slot != firstused)) {
		/* This possibly is a firmware bug and will result in
		 * malfunction, memory leaks and/or stall of DMA functionality. */
		b43dbg(dev->wl, "Out of order TX status report on DMA ring %d. "
		       "Expected %d, but got %d\n",
		       ring->index, firstused, slot);
		return;
	}

	ops = ring->ops;
	while (1) {
		B43_WARN_ON(slot < 0 || slot >= ring->nr_slots);
		desc = ops->idx2desc(ring, slot, &meta);

		if (b43_dma_ptr_is_poisoned(meta->skb)) {
			b43dbg(dev->wl, "Poisoned TX slot %d (first=%d) "
			       "on ring %d\n",
			       slot, firstused, ring->index);
			break;
		}
		if (meta->skb) {
			struct b43_private_tx_info *priv_info =
				b43_get_priv_tx_info(IEEE80211_SKB_CB(meta->skb));

			unmap_descbuffer(ring, meta->dmaaddr, meta->skb->len, 1);
			kfree(priv_info->bouncebuffer);
			priv_info->bouncebuffer = NULL;
		} else {
			unmap_descbuffer(ring, meta->dmaaddr,
					 b43_txhdr_size(dev), 1);
		}

		if (meta->is_last_fragment) {
			struct ieee80211_tx_info *info;

			if (unlikely(!meta->skb)) {
				/* This is a scatter-gather fragment of a frame, so
				 * the skb pointer must not be NULL. */
				b43dbg(dev->wl, "TX status unexpected NULL skb "
				       "at slot %d (first=%d) on ring %d\n",
				       slot, firstused, ring->index);
				break;
			}

			info = IEEE80211_SKB_CB(meta->skb);

			/*
			 * Call back to inform the ieee80211 subsystem about
			 * the status of the transmission.
			 */
			frame_succeed = b43_fill_txstatus_report(dev, info, status);
#ifdef CONFIG_B43_DEBUG
			if (frame_succeed)
				ring->nr_succeed_tx_packets++;
			else
				ring->nr_failed_tx_packets++;
			ring->nr_total_packet_tries += status->frame_count;
#endif /* DEBUG */
			ieee80211_tx_status(dev->wl->hw, meta->skb);

			/* skb will be freed by ieee80211_tx_status().
			 * Poison our pointer. */
			meta->skb = B43_DMA_PTR_POISON;
		} else {
			/* No need to call free_descriptor_buffer here, as
			 * this is only the txhdr, which is not allocated.
			 */
			if (unlikely(meta->skb)) {
				b43dbg(dev->wl, "TX status unexpected non-NULL skb "
				       "at slot %d (first=%d) on ring %d\n",
				       slot, firstused, ring->index);
				break;
			}
		}

		/* Everything unmapped and free'd. So it's not used anymore. */
		ring->used_slots--;

		if (meta->is_last_fragment) {
			/* This is the last scatter-gather
			 * fragment of the frame. We are done. */
			break;
		}
		slot = next_slot(ring, slot);
	}
	if (ring->stopped) {
		B43_WARN_ON(free_slots(ring) < TX_SLOTS_PER_FRAME);
		ieee80211_wake_queue(dev->wl->hw, ring->queue_prio);
		ring->stopped = 0;
		if (b43_debug(dev, B43_DBG_DMAVERBOSE)) {
			b43dbg(dev->wl, "Woke up TX ring %d\n", ring->index);
		}
	}
}

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.