linux-kernel - [PATCH][V2] flow dissector: check if arp

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Message-Id: <20170113184820.823-1-colin.king@canonical.com>
Date:   Fri, 13 Jan 2017 18:48:20 +0000
From:   Colin King <colin.king@...onical.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Alexander Duyck <aduyck@...antis.com>,
        Jiri Pirko <jiri@...lanox.com>,
        Tom Herbert <tom@...bertland.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Hadar Hen Zion <hadarh@...lanox.com>,
        Simon Horman <simon.horman@...ronome.com>,
        Gao Feng <fgao@...ai8.com>, Amir Vadai <amir@...ai.me>,
        netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH][V2] flow dissector: check if arp_eth is null rather than arp

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

arp is being checked instead of arp_eth to see if the call to
__skb_header_pointer failed. Fix this by checking arp_eth is
null instead of arp.   Also fix to use length hlen rather than
hlen - sizeof(_arp); thanks to Eric Dumazet for spotting
this latter issue.

CoverityScan CID#1396428 ("Logically dead code") on 2nd
arp comparison (which should be arp_eth instead).

Fixes: commit 55733350e5e8b70c5 ("flow disector: ARP support")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 net/core/flow_dissector.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index e3dffc7..c35aae1 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -407,9 +407,9 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 
 		arp_eth = __skb_header_pointer(skb, nhoff + sizeof(_arp),
 					       sizeof(_arp_eth), data,
-					       hlen - sizeof(_arp),
+					       hlen,
 					       &_arp_eth);
-		if (!arp)
+		if (!arp_eth)
 			goto out_bad;
 
 		if (dissector_uses_key(flow_dissector,
-- 
2.10.2