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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
CC:     Alexander Kochetkov <al.kochet@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.14 034/110] net: arc_emac: fix arc_emac_rx()
 error paths
Thread-Topic: [PATCH AUTOSEL for 4.14 034/110] net: arc_emac: fix
 arc_emac_rx() error paths
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Date:   Sat, 3 Feb 2018 18:00:45 +0000
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From: Alexander Kochetkov <al.kochet@gmail.com>

[ Upstream commit e688822d035b494071ecbadcccbd6f3325fb0f59 ]

arc_emac_rx() has some issues found by code review.

In case netdev_alloc_skb_ip_align() or dma_map_single() failure
rx fifo entry will not be returned to EMAC.

In case dma_map_single() failure previously allocated skb became
lost to driver. At the same time address of newly allocated skb
will not be provided to EMAC.

Signed-off-by: Alexander Kochetkov <al.kochet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 drivers/net/ethernet/arc/emac_main.c | 53 +++++++++++++++++++++-----------=
----
 1 file changed, 31 insertions(+), 22 deletions(-)

diff --git a/drivers/net/ethernet/arc/emac_main.c b/drivers/net/ethernet/ar=
c/emac_main.c
index 3241af1ce718..5b422be56165 100644
--- a/drivers/net/ethernet/arc/emac_main.c
+++ b/drivers/net/ethernet/arc/emac_main.c
@@ -210,39 +210,48 @@ static int arc_emac_rx(struct net_device *ndev, int b=
udget)
 			continue;
 		}
=20
-		pktlen =3D info & LEN_MASK;
-		stats->rx_packets++;
-		stats->rx_bytes +=3D pktlen;
-		skb =3D rx_buff->skb;
-		skb_put(skb, pktlen);
-		skb->dev =3D ndev;
-		skb->protocol =3D eth_type_trans(skb, ndev);
-
-		dma_unmap_single(&ndev->dev, dma_unmap_addr(rx_buff, addr),
-				 dma_unmap_len(rx_buff, len), DMA_FROM_DEVICE);
-
-		/* Prepare the BD for next cycle */
-		rx_buff->skb =3D netdev_alloc_skb_ip_align(ndev,
-							 EMAC_BUFFER_SIZE);
-		if (unlikely(!rx_buff->skb)) {
+		/* Prepare the BD for next cycle. netif_receive_skb()
+		 * only if new skb was allocated and mapped to avoid holes
+		 * in the RX fifo.
+		 */
+		skb =3D netdev_alloc_skb_ip_align(ndev, EMAC_BUFFER_SIZE);
+		if (unlikely(!skb)) {
+			if (net_ratelimit())
+				netdev_err(ndev, "cannot allocate skb\n");
+			/* Return ownership to EMAC */
+			rxbd->info =3D cpu_to_le32(FOR_EMAC | EMAC_BUFFER_SIZE);
 			stats->rx_errors++;
-			/* Because receive_skb is below, increment rx_dropped */
 			stats->rx_dropped++;
 			continue;
 		}
=20
-		/* receive_skb only if new skb was allocated to avoid holes */
-		netif_receive_skb(skb);
-
-		addr =3D dma_map_single(&ndev->dev, (void *)rx_buff->skb->data,
+		addr =3D dma_map_single(&ndev->dev, (void *)skb->data,
 				      EMAC_BUFFER_SIZE, DMA_FROM_DEVICE);
 		if (dma_mapping_error(&ndev->dev, addr)) {
 			if (net_ratelimit())
-				netdev_err(ndev, "cannot dma map\n");
-			dev_kfree_skb(rx_buff->skb);
+				netdev_err(ndev, "cannot map dma buffer\n");
+			dev_kfree_skb(skb);
+			/* Return ownership to EMAC */
+			rxbd->info =3D cpu_to_le32(FOR_EMAC | EMAC_BUFFER_SIZE);
 			stats->rx_errors++;
+			stats->rx_dropped++;
 			continue;
 		}
+
+		/* unmap previosly mapped skb */
+		dma_unmap_single(&ndev->dev, dma_unmap_addr(rx_buff, addr),
+				 dma_unmap_len(rx_buff, len), DMA_FROM_DEVICE);
+
+		pktlen =3D info & LEN_MASK;
+		stats->rx_packets++;
+		stats->rx_bytes +=3D pktlen;
+		skb_put(rx_buff->skb, pktlen);
+		rx_buff->skb->dev =3D ndev;
+		rx_buff->skb->protocol =3D eth_type_trans(rx_buff->skb, ndev);
+
+		netif_receive_skb(rx_buff->skb);
+
+		rx_buff->skb =3D skb;
 		dma_unmap_addr_set(rx_buff, addr, addr);
 		dma_unmap_len_set(rx_buff, len, EMAC_BUFFER_SIZE);
=20
--=20
2.11.0