linux-kernel - [PATCH 4.2 074/124] net: mvneta: fix error path for building skb

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Date:	Mon,  7 Dec 2015 09:56:04 -0500
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Marcin Wojtas <mw@...ihalf.com>,
	Simon Guinot <simon.guinot@...uanux.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.2 074/124] net: mvneta: fix error path for building skb

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

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

From: Marcin Wojtas <mw@...ihalf.com>

commit 26c17a179f3f64f92de6e837c14279a6431a7ab6 upstream.

In the actual RX processing, there is same error path for both descriptor
ring refilling and building skb fails. This is not correct, because after
successful refill, the ring is already updated with newly allocated
buffer. Then, in case of build_skb() fail, hitherto code left the original
buffer unmapped.

This patch fixes above situation by swapping error check of skb build with
DMA-unmap of original buffer.

Signed-off-by: Marcin Wojtas <mw@...ihalf.com>
Acked-by: Simon Guinot <simon.guinot@...uanux.org>
Fixes a84e32894191 ("net: mvneta: fix refilling for Rx DMA buffers")
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/net/ethernet/marvell/mvneta.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -1533,12 +1533,16 @@ static int mvneta_rx(struct mvneta_port
 		}

 		skb = build_skb(data, pp->frag_size > PAGE_SIZE ? 0 : pp->frag_size);
-		if (!skb)
-			goto err_drop_frame;

+		/* After refill old buffer has to be unmapped regardless
+		 * the skb is successfully built or not.
+		 */
 		dma_unmap_single(dev->dev.parent, phys_addr,
 				 MVNETA_RX_BUF_SIZE(pp->pkt_size), DMA_FROM_DEVICE);

+		if (!skb)
+			goto err_drop_frame;
+
 		rcvd_pkts++;
 		rcvd_bytes += rx_bytes;

--
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