netdev - [PATCH net v2 4/4] ipv6: add defensive check for CHECKSUM_PARTIAL skbs in ip

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Message-Id: <1445958135-19805-5-git-send-email-hannes@stressinduktion.org>
Date:	Tue, 27 Oct 2015 16:02:15 +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 4/4] ipv6: 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.

Fixes: commit 32dce968dd987 ("ipv6: Allow for partial checksums on non-ufo packets")
See-also: commit 72e843bb09d45 ("ipv6: ip6_fragment() should check CHECKSUM_PARTIAL")
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/ipv6/ip6_output.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 9828a71..c6c5630 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -605,6 +605,10 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 	frag_id = ipv6_select_ident(net, &ipv6_hdr(skb)->daddr,
 				    &ipv6_hdr(skb)->saddr);
 
+	if (WARN_ON_ONCE(skb->ip_summed == CHECKSUM_PARTIAL) &&
+	    (err = skb_checksum_help(skb)))
+		goto fail;
+
 	hroom = LL_RESERVED_SPACE(rt->dst.dev);
 	if (skb_has_frag_list(skb)) {
 		int first_len = skb_pagelen(skb);
@@ -733,10 +737,6 @@ slow_path_clean:
 	}
 
 slow_path:
-	if ((skb->ip_summed == CHECKSUM_PARTIAL) &&
-	    skb_checksum_help(skb))
-		goto fail;
-
 	left = skb->len - hlen;		/* Space per frame */
 	ptr = hlen;			/* Where to start from */
 
-- 
2.5.0

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