netdev - [PATCH AUTOSEL 5.11 01/61] mt76: fix tx skb error handling in mt76_dma_tx_queue

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Date:   Tue, 16 Mar 2021 20:54:35 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Felix Fietkau <nbd@....name>, Kalle Valo <kvalo@...eaurora.org>,
        Sasha Levin <sashal@...nel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: [PATCH AUTOSEL 5.11 01/61] mt76: fix tx skb error handling in mt76_dma_tx_queue_skb

From: Felix Fietkau <nbd@....name>

[ Upstream commit ae064fc0e32a4d28389086d9f4b260a0c157cfee ]

When running out of room in the tx queue after calling drv->tx_prepare_skb,
the buffer list will already have been modified on MT7615 and newer drivers.
This can leak a DMA mapping and will show up as swiotlb allocation failures
on x86.

Fix this by moving the queue length check further up. This is less accurate,
since it can overestimate the needed room in the queue on MT7615 and newer,
but the difference is small enough to not matter in practice.

Signed-off-by: Felix Fietkau <nbd@....name>
Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
Link: https://lore.kernel.org/r/20210216135119.23809-1-nbd@nbd.name
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/wireless/mediatek/mt76/dma.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/dma.c b/drivers/net/wireless/mediatek/mt76/dma.c
index e81dfaf99bcb..372f27687f2d 100644
--- a/drivers/net/wireless/mediatek/mt76/dma.c
+++ b/drivers/net/wireless/mediatek/mt76/dma.c
@@ -345,7 +345,6 @@ mt76_dma_tx_queue_skb(struct mt76_dev *dev, struct mt76_queue *q,
 	};
 	struct ieee80211_hw *hw;
 	int len, n = 0, ret = -ENOMEM;
-	struct mt76_queue_entry e;
 	struct mt76_txwi_cache *t;
 	struct sk_buff *iter;
 	dma_addr_t addr;
@@ -387,6 +386,11 @@ mt76_dma_tx_queue_skb(struct mt76_dev *dev, struct mt76_queue *q,
 	}
 	tx_info.nbuf = n;
 
+	if (q->queued + (tx_info.nbuf + 1) / 2 >= q->ndesc - 1) {
+		ret = -ENOMEM;
+		goto unmap;
+	}
+
 	dma_sync_single_for_cpu(dev->dev, t->dma_addr, dev->drv->txwi_size,
 				DMA_TO_DEVICE);
 	ret = dev->drv->tx_prepare_skb(dev, txwi, q->qid, wcid, sta, &tx_info);
@@ -395,11 +399,6 @@ mt76_dma_tx_queue_skb(struct mt76_dev *dev, struct mt76_queue *q,
 	if (ret < 0)
 		goto unmap;
 
-	if (q->queued + (tx_info.nbuf + 1) / 2 >= q->ndesc - 1) {
-		ret = -ENOMEM;
-		goto unmap;
-	}
-
 	return mt76_dma_add_buf(dev, q, tx_info.buf, tx_info.nbuf,
 				tx_info.info, tx_info.skb, t);
 
@@ -415,9 +414,7 @@ mt76_dma_tx_queue_skb(struct mt76_dev *dev, struct mt76_queue *q,
 		dev->test.tx_done--;
 #endif
 
-	e.skb = tx_info.skb;
-	e.txwi = t;
-	dev->drv->tx_complete_skb(dev, &e);
+	dev_kfree_skb(tx_info.skb);
 	mt76_put_txwi(dev, t);
 	return ret;
 }
-- 
2.30.1