netdev - [PATCH net v2 2/4] ipv4: add defensive check for CHECKSUM_PARTIAL skbs in ip

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Message-Id: <1445958135-19805-3-git-send-email-hannes@stressinduktion.org>
Date:	Tue, 27 Oct 2015 16:02:13 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	netdev@...r.kernel.org
Cc:	edumazet@...gle.com, vyasevich@...il.com, bcodding@...hat.com,
	tom@...bertland.com,
	Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: [PATCH net v2 2/4] ipv4: add defensive check for CHECKSUM_PARTIAL skbs in ip_fragment

CHECKSUM_PARTIAL skbs should never arrive in ip_fragment. If we get one
of those warn about them once and handle them gracefully by recalculating
the checksum.

Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Vlad Yasevich <vyasevich@...il.com>
Cc: Benjamin Coddington <bcodding@...hat.com>
Cc: Tom Herbert <tom@...bertland.com>
Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
---
 net/ipv4/ip_output.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 0b02417..3f94a3b 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -533,6 +533,11 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 
 	dev = rt->dst.dev;
 
+	/* for offloaded checksums cleanup checksum before fragmentation */
+	if (WARN_ON_ONCE(skb->ip_summed == CHECKSUM_PARTIAL) &&
+	    (err = skb_checksum_help(skb)))
+		goto fail;
+
 	/*
 	 *	Point into the IP datagram header.
 	 */
@@ -657,9 +662,6 @@ slow_path_clean:
 	}
 
 slow_path:
-	/* for offloaded checksums cleanup checksum before fragmentation */
-	if ((skb->ip_summed == CHECKSUM_PARTIAL) && skb_checksum_help(skb))
-		goto fail;
 	iph = ip_hdr(skb);
 
 	left = skb->len - hlen;		/* Space per frame */
-- 
2.5.0

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