netdev - [PATCH net-next] net: enetc: fix array underflow in error handling code

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Date:   Fri, 9 Apr 2021 15:24:28 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Claudiu Manoil <claudiu.manoil@....com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Vladimir Oltean <vladimir.oltean@....com>,
        netdev@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH net-next] net: enetc: fix array underflow in error handling
 code

This loop will try to unmap enetc_unmap_tx_buff[-1] and crash.

Fixes: 9d2b68cc108d ("net: enetc: add support for XDP_REDIRECT")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
 drivers/net/ethernet/freescale/enetc/enetc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
index 57049ae97201..d86395775ed0 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc.c
@@ -895,7 +895,7 @@ static int enetc_xdp_frame_to_xdp_tx_swbd(struct enetc_bdr *tx_ring,
 		dma = dma_map_single(tx_ring->dev, data, len, DMA_TO_DEVICE);
 		if (unlikely(dma_mapping_error(tx_ring->dev, dma))) {
 			/* Undo the DMA mapping for all fragments */
-			while (n-- >= 0)
+			while (--n >= 0)
 				enetc_unmap_tx_buff(tx_ring, &xdp_tx_arr[n]);
 
 			netdev_err(tx_ring->ndev, "DMA map error\n");
-- 
2.30.2