netdev - [PATCH ipsec] xfrm: esp6: fix the location of the transport header with encapsulation

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Message-Id: <2159be20972bd53beefeb0b8ad31adac2792105d.1595858511.git.sd@queasysnail.net>
Date:   Mon, 27 Jul 2020 16:03:47 +0200
From:   Sabrina Dubroca <sd@...asysnail.net>
To:     netdev@...r.kernel.org
Cc:     steffen.klassert@...unet.com, Sabrina Dubroca <sd@...asysnail.net>,
        Xiumei Mu <xmu@...hat.com>
Subject: [PATCH ipsec] xfrm: esp6: fix the location of the transport header with encapsulation

commit 17175d1a27c6 ("xfrm: esp6: fix encapsulation header offset
computation") changed esp6_input_done2 to correctly find the size of
the IPv6 header that precedes the TCP/UDP encapsulation header, but
didn't adjust the final call to skb_set_transport_header, which I
assumed was correct in using skb_network_header_len.

Xiumei Mu reported that when we create xfrm states that include port
numbers in the selector, traffic from the user sockets is dropped. It
turns out that we get a state mismatch in __xfrm_policy_check, because
we end up trying to compare the encapsulation header's ports with the
selector that's based on user traffic ports.

Fixes: 0146dca70b87 ("xfrm: add support for UDPv6 encapsulation of ESP")
Fixes: 26333c37fc28 ("xfrm: add IPv6 support for espintcp")
Reported-by: Xiumei Mu <xmu@...hat.com>
Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
---
 net/ipv6/esp6.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index 55ae70be91b3..52c2f063529f 100644
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -815,6 +815,7 @@ int esp6_input_done2(struct sk_buff *skb, int err)
 		offset = ipv6_skip_exthdr(skb, offset, &nexthdr, &frag_off);
 		uh = (void *)(skb->data + offset);
 		th = (void *)(skb->data + offset);
+		hdr_len += offset;

 		switch (x->encap->encap_type) {
 		case TCP_ENCAP_ESPINTCP:
-- 
2.27.0