[PATCH 6.1.y] net: macb: drop in-flight Tx SKBs on close

[Sasha Levin <sashal@kernel.org>]

From: Théo Lebrun <theo.lebrun@bootlin.com>

[ Upstream commit 27f575836cfebbf872dec020428742b10650a955 ]

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, queues' tx_skb just got allocated and are empty.

Fixes: 89e5785fc8a6 ("[PATCH] Atmel MACB ethernet driver")
Cc: stable@vger.kernel.org
Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Link: https://patch.msgid.link/20260702-macb-drop-tx-v4-1-1c833eebdbc8@bootlin.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
[ adjusted context to free each queue's Tx/Rx rings individually since 6.12 lacks the single-dma_alloc_coherent refactor ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 f29dc2d3621903..513a1267a6ef7e 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -2520,8 +2520,26 @@ static void macb_free_consistent(struct macb *bp)
 	bp->macbgem_ops.mog_free_rx_buffers(bp);
 
 	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);
+			}
+
+			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;
+
 		if (queue->tx_ring) {
 			size = TX_RING_BYTES(bp) + bp->tx_bd_rd_prefetch;
 			dma_free_coherent(&bp->pdev->dev, size,
-- 
2.53.0