[PATCH 3.16.y-ckt 032/104] net: mvneta: fix DMA buffer unmapping in mvneta_rx()

[Luis Henriques]

3.16.7-ckt19 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Simon Guinot <simon.guinot at sequanux.org>

commit daf158d0d544cec80b7b30deff8cfc59a6e17610 upstream.

This patch fixes a regression introduced by the commit a84e32894191
("net: mvneta: fix refilling for Rx DMA buffers"). Due to this commit
the newly allocated Rx buffers are DMA-unmapped in place of those passed
to the networking stack. Obviously, this causes data corruptions.

This patch fixes the issue by ensuring that the right Rx buffers are
DMA-unmapped.

Reported-by: Oren Laskin <oren at igneous.io>
Signed-off-by: Simon Guinot <simon.guinot at sequanux.org>
Fixes: a84e32894191 ("net: mvneta: fix refilling for Rx DMA buffers")
Tested-by: Oren Laskin <oren at igneous.io>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/net/ethernet/marvell/mvneta.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index 109908574224..03ab691ad683 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -1450,6 +1450,7 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo,
 		struct mvneta_rx_desc *rx_desc = mvneta_rxq_next_desc_get(rxq);
 		struct sk_buff *skb;
 		unsigned char *data;
+		dma_addr_t phys_addr;
 		u32 rx_status;
 		int rx_bytes, err;
 
@@ -1457,6 +1458,7 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo,
 		rx_status = rx_desc->status;
 		rx_bytes = rx_desc->data_size - (ETH_FCS_LEN + MVNETA_MH_SIZE);
 		data = (unsigned char *)rx_desc->buf_cookie;
+		phys_addr = rx_desc->buf_phys_addr;
 
 		if (!mvneta_rxq_desc_is_first_last(rx_status) ||
 		    (rx_status & MVNETA_RXD_ERR_SUMMARY)) {
@@ -1505,7 +1507,7 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo,
 		if (!skb)
 			goto err_drop_frame;
 
-		dma_unmap_single(dev->dev.parent, rx_desc->buf_phys_addr,
+		dma_unmap_single(dev->dev.parent, phys_addr,
 				 MVNETA_RX_BUF_SIZE(pp->pkt_size), DMA_FROM_DEVICE);
 
 		rcvd_pkts++;