From 57406e7373220412437a025d6abc10031e9acafd Mon Sep 17 00:00:00 2001
From: Colin Ian King <colin.king@canonical.com>
Date: Fri, 18 Aug 2017 12:11:50 +0100
Subject: nfp: fix infinite loop on umapping cleanup

[ Upstream commit eac2c68d663effb077210218788952b5a0c1f60e ]

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@canonical.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
index aee3fd2..4ca82bd 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
@@ -871,8 +871,7 @@ 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(&nn->pdev->dev,
 			       tx_ring->txbufs[wr_idx].dma_addr,
-- 
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