[PATCH net v2 2/4] net: macb: drop in-flight Tx SKBs on close

["Théo Lebrun" <theo.lebrun@bootlin.com>]

The MACB driver has since forever leaked the outgoing SKBs that
have not yet been marked as completed. They live in queue->tx_skb
which gets freed without remorse nor checking.

macb_free_consistent() gets called in a few codepaths, but only
close will trigger the added expressions. In macb_open() and
macb_alloc_consistent() failure cases, tx_skb just got allocated
and is empty.

Use the new macb_tx_unmap() prototype to report our error as
SKB_DROP_REASON_NOT_SPECIFIED rather than SKB_CONSUMED which makes it
sound like no error occurred. Equivalent to dev_kfree_skb_any().

Fixes: 89e5785fc8a6 ("[PATCH] Atmel MACB ethernet driver")
Cc: stable@vger.kernel.org
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
---
 drivers/net/ethernet/cadence/macb_main.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 9caae1ef52b1..5a2500bd59a6 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -2678,8 +2678,26 @@ static void macb_free_consistent(struct macb *bp)
 	dma_free_coherent(dev, size, bp->queues[0].rx_ring, bp->queues[0].rx_ring_dma);
 
 	for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) {
-		kfree(queue->tx_skb);
-		queue->tx_skb = NULL;
+		if (queue->tx_skb) {
+			unsigned int dropped = 0, tail;
+
+			for (tail = queue->tx_tail; tail != queue->tx_head;
+			     tail++) {
+				if (macb_tx_skb(queue, tail)->skb)
+					dropped++;
+				macb_tx_unmap(bp, macb_tx_skb(queue, tail), 0,
+					      SKB_DROP_REASON_NOT_SPECIFIED);
+			}
+
+			queue->stats.tx_dropped += dropped;
+			bp->dev->stats.tx_dropped += dropped;
+
+			kfree(queue->tx_skb);
+			queue->tx_skb = NULL;
+		}
+
+		queue->tx_head = 0;
+		queue->tx_tail = 0;
 		queue->tx_ring = NULL;
 		queue->rx_ring = NULL;
 	}

-- 
2.54.0