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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Davide Caratti <dcaratti@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.4 030/134] sched: act_csum: dont mangle TCP and UDP GSO packets
Date:   Mon, 19 Mar 2018 19:05:13 +0100
Message-Id: <20180319171853.609141589@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Davide Caratti <dcaratti@redhat.com>


[ Upstream commit add641e7dee31b36aee83412c29e39dd1f5e0c9c ]

after act_csum computes the checksum on skbs carrying GSO TCP/UDP packets,
subsequent segmentation fails because skb_needs_check(skb, true) returns
true. Because of that, skb_warn_bad_offload() is invoked and the following
message is displayed:

WARNING: CPU: 3 PID: 28 at net/core/dev.c:2553 skb_warn_bad_offload+0xf0/0xfd
<...>

  [<ffffffff8171f486>] skb_warn_bad_offload+0xf0/0xfd
  [<ffffffff8161304c>] __skb_gso_segment+0xec/0x110
  [<ffffffff8161340d>] validate_xmit_skb+0x12d/0x2b0
  [<ffffffff816135d2>] validate_xmit_skb_list+0x42/0x70
  [<ffffffff8163c560>] sch_direct_xmit+0xd0/0x1b0
  [<ffffffff8163c760>] __qdisc_run+0x120/0x270
  [<ffffffff81613b3d>] __dev_queue_xmit+0x23d/0x690
  [<ffffffff81613fa0>] dev_queue_xmit+0x10/0x20

Since GSO is able to compute checksum on individual segments of such skbs,
we can simply skip mangling the packet.

Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/sched/act_csum.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/net/sched/act_csum.c
+++ b/net/sched/act_csum.c
@@ -175,6 +175,9 @@ static int tcf_csum_ipv4_tcp(struct sk_b
 	struct tcphdr *tcph;
 	const struct iphdr *iph;
 
+	if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
+		return 1;
+
 	tcph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*tcph));
 	if (tcph == NULL)
 		return 0;
@@ -196,6 +199,9 @@ static int tcf_csum_ipv6_tcp(struct sk_b
 	struct tcphdr *tcph;
 	const struct ipv6hdr *ip6h;
 
+	if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
+		return 1;
+
 	tcph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*tcph));
 	if (tcph == NULL)
 		return 0;
@@ -219,6 +225,9 @@ static int tcf_csum_ipv4_udp(struct sk_b
 	const struct iphdr *iph;
 	u16 ul;
 
+	if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type & SKB_GSO_UDP)
+		return 1;
+
 	/*
 	 * Support both UDP and UDPLITE checksum algorithms, Don't use
 	 * udph->len to get the real length without any protocol check,
@@ -272,6 +281,9 @@ static int tcf_csum_ipv6_udp(struct sk_b
 	const struct ipv6hdr *ip6h;
 	u16 ul;
 
+	if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type & SKB_GSO_UDP)
+		return 1;
+
 	/*
 	 * Support both UDP and UDPLITE checksum algorithms, Don't use
 	 * udph->len to get the real length without any protocol check,