[PATCH net v2 1/2] xfrm6: Fix IPv6 payload_len in xfrm6_transport_finish

From: Yossi Kuperman <redacted>

IPv6 payload length indicates the size of the payload, including any
extension headers.

In xfrm6_transport_finish, ipv6_hdr(skb)->payload_len is set to the
payload size only, regardless of the presence of any extension headers.
After ESP GRO transport mode decapsulation, ipv6_rcv trims the packet
according to the wrong payload_len, thus corrupting the packet.

Set payload_len to account for extension headers as well.

Fixes: 7785bba299a8 ("esp: Add a software GRO codepath")
Signed-off-by: Yossi Kuperman <redacted>
---
v1 -> v2:
	- Fix the "Fixes" tag
---
 net/ipv6/xfrm6_input.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/xfrm6_input.c b/net/ipv6/xfrm6_input.c
index 08a807b..3ef5d91 100644
--- a/net/ipv6/xfrm6_input.c
+++ b/net/ipv6/xfrm6_input.c

@@ -43,8 +43,8 @@ int xfrm6_transport_finish(struct sk_buff *skb, int async)
 		return 1;
 #endif
 
-	ipv6_hdr(skb)->payload_len = htons(skb->len);
 	__skb_push(skb, skb->data - skb_network_header(skb));
+	ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 
 	if (xo && (xo->flags & XFRM_GRO)) {
 		skb_mac_header_rebuild(skb);

-- 
2.8.1

From: Yossi Kuperman <redacted>

IP6CB(skb)->nhoff is the offset of the nexthdr field in an IPv6
header, unless there are extension headers present, in which case
nhoff points to the nexthdr field of the last extension header.

In non-GRO code path, nhoff is set by ipv6_rcv before any XFRM code
is executed. Conversely, in GRO code path (when esp6_offload is loaded),
nhoff is not set. The following functions fail to read the correct value
and eventually the packet is dropped:

    xfrm6_transport_finish
    xfrm6_tunnel_input
    xfrm6_rcv_tnl

Set nhoff to the proper offset of nexthdr in esp6_gro_receive.

Fixes: 7785bba299a8 ("esp: Add a software GRO codepath")
Signed-off-by: Yossi Kuperman <redacted>
---
 net/ipv6/esp6_offload.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/net/ipv6/esp6_offload.c b/net/ipv6/esp6_offload.c
index d950d43..f02f131 100644
--- a/net/ipv6/esp6_offload.c
+++ b/net/ipv6/esp6_offload.c

@@ -30,6 +30,25 @@
 #include <net/ipv6.h>
 #include <linux/icmpv6.h>
 
+static __u16 esp6_nexthdr_esp_offset(struct ipv6hdr *ipv6_hdr, int nhlen)
+{
+	int off = sizeof(struct ipv6hdr);
+	struct ipv6_opt_hdr *exthdr;
+
+	if (likely(ipv6_hdr->nexthdr == NEXTHDR_ESP))
+		return offsetof(struct ipv6hdr, nexthdr);
+
+	while (off < nhlen) {
+		exthdr = (void *)ipv6_hdr + off;
+		if (exthdr->nexthdr == NEXTHDR_ESP)
+			return off;
+
+		off += ipv6_optlen(exthdr);
+	}
+
+	return 0;
+}
+
 static struct sk_buff **esp6_gro_receive(struct sk_buff **head,
 					 struct sk_buff *skb)
 {

@@ -38,6 +57,7 @@ static struct sk_buff **esp6_gro_receive(struct sk_buff **head,
 	struct xfrm_state *x;
 	__be32 seq;
 	__be32 spi;
+	int nhoff;
 	int err;
 
 	skb_pull(skb, offset);

@@ -72,6 +92,11 @@ static struct sk_buff **esp6_gro_receive(struct sk_buff **head,
 
 	xo->flags |= XFRM_GRO;
 
+	nhoff = esp6_nexthdr_esp_offset(ipv6_hdr(skb), offset);
+	if (!nhoff)
+		goto out;
+
+	IP6CB(skb)->nhoff = nhoff;
 	XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip6 = NULL;
 	XFRM_SPI_SKB_CB(skb)->family = AF_INET6;
 	XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct ipv6hdr, daddr);

-- 
2.8.1

On Thu, Jun 22, 2017 at 11:37:11AM +0300, yossiku@mellanox.com wrote:

From: Yossi Kuperman <redacted>

IP6CB(skb)->nhoff is the offset of the nexthdr field in an IPv6
header, unless there are extension headers present, in which case
nhoff points to the nexthdr field of the last extension header.

In non-GRO code path, nhoff is set by ipv6_rcv before any XFRM code
is executed. Conversely, in GRO code path (when esp6_offload is loaded),
nhoff is not set. The following functions fail to read the correct value
and eventually the packet is dropped:

    xfrm6_transport_finish
    xfrm6_tunnel_input
    xfrm6_rcv_tnl

Set nhoff to the proper offset of nexthdr in esp6_gro_receive.

Fixes: 7785bba299a8 ("esp: Add a software GRO codepath")
Signed-off-by: Yossi Kuperman <redacted>

Both patches applied, thanks for your work Yossi!