[PATCH 4.9 06/78] gre6: Fix reception with IP6_TNL_F_RCV_DSCP_COPY

Greg Kroah-Hartman
2020-09-01T17:14:42Z

From: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz>

[ Upstream commit 272502fcb7cda01ab07fc2fcff82d1d2f73d43cc ]

When receiving an IPv4 packet inside an IPv6 GRE packet, and the
IP6_TNL_F_RCV_DSCP_COPY flag is set on the tunnel, the IPv4 header would
get corrupted. This is due to the common ip6_tnl_rcv() function assuming
that the inner header is always IPv6. This patch checks the tunnel
protocol for IPv4 inner packets, but still defaults to IPv6.

Fixes: 308edfdf1563 ("gre6: Cleanup GREv6 receive path, call common GRE functions")
Signed-off-by: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv6/ip6_tunnel.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -871,7 +871,15 @@ int ip6_tnl_rcv(struct ip6_tnl *t, struc
struct metadata_dst *tun_dst,
bool log_ecn_err)
{
- return __ip6_tnl_rcv(t, skb, tpi, NULL, ip6ip6_dscp_ecn_decapsulate,
+ int (*dscp_ecn_decapsulate)(const struct ip6_tnl *t,
+ const struct ipv6hdr *ipv6h,
+ struct sk_buff *skb);
+
+ dscp_ecn_decapsulate = ip6ip6_dscp_ecn_decapsulate;
+ if (tpi->proto == htons(ETH_P_IP))
+ dscp_ecn_decapsulate = ip4ip6_dscp_ecn_decapsulate;
+
+ return __ip6_tnl_rcv(t, skb, tpi, NULL, dscp_ecn_decapsulate,
log_ecn_err);
}
EXPORT_SYMBOL(ip6_tnl_rcv);