linux-kernel - [PATCH] nfp: fix infinite loop on umapping cleanup

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Date:   Fri, 18 Aug 2017 12:11:50 +0100
From:   Colin King <colin.king@...onical.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Simon Horman <simon.horman@...ronome.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        oss-drivers@...ronome.com, netdev@...r.kernel.org
Cc:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] nfp: fix infinite loop on umapping cleanup

From: Colin Ian King <colin.king@...onical.com>

The while loop that performs the dma page unmapping never decrements
index counter f and hence loops forever. Fix this with a pre-decrement
on f.

Detected by CoverityScan, CID#1357309 ("Infinite loop")

Fixes: 4c3523623dc0 ("net: add driver for Netronome NFP4000/NFP6000 NIC VFs")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/net/ethernet/netronome/nfp/nfp_net_common.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
index 4a990033c4d5..732f1d315fba 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
@@ -908,8 +908,7 @@ static int nfp_net_tx(struct sk_buff *skb, struct net_device *netdev)
 	return NETDEV_TX_OK;
 
 err_unmap:
-	--f;
-	while (f >= 0) {
+	while (--f >= 0) {
 		frag = &skb_shinfo(skb)->frags[f];
 		dma_unmap_page(dp->dev, tx_ring->txbufs[wr_idx].dma_addr,
 			       skb_frag_size(frag), DMA_TO_DEVICE);
-- 
2.11.0