xfrm: Add xfrm_tunnel_skb_cb to the skb common buffer

IPsec vti_rcv needs to remind the tunnel pointer to
check it later at the vti_rcv_cb callback. So add
this pointer to the IPsec common buffer, initialize
it and check it to avoid transport state matching of
a tunneled packet.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

3 files changed, 50 insertions, 12 deletions

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 345a15084557..33112599fa47 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -599,16 +599,27 @@ struct xfrm_mgr {
 int xfrm_register_km(struct xfrm_mgr *km);
 int xfrm_unregister_km(struct xfrm_mgr *km);
 
+struct xfrm_tunnel_skb_cb {
+        union {
+                struct inet_skb_parm h4;
+                struct inet6_skb_parm h6;
+        } header;
+
+        union {
+                struct ip_tunnel *ip4;
+                struct ip6_tnl *ip6;
+        } tunnel;
+};
+
+#define XFRM_TUNNEL_SKB_CB(__skb) ((struct xfrm_tunnel_skb_cb *)&((__skb)->cb[0]))
+
 /*
  * This structure is used for the duration where packets are being
  * transformed by IPsec.  As soon as the packet leaves IPsec the
  * area beyond the generic IP part may be overwritten.
  */
 struct xfrm_skb_cb {
-        union {
-                struct inet_skb_parm h4;
-                struct inet6_skb_parm h6;
-        } header;
+        struct xfrm_tunnel_skb_cb header;
 
         /* Sequence number for replay protection. */
         union {
@@ -630,10 +641,7 @@ struct xfrm_skb_cb {
  * to transmit header information to the mode input/output functions.
  */
 struct xfrm_mode_skb_cb {
-        union {
-                struct inet_skb_parm h4;
-                struct inet6_skb_parm h6;
-        } header;
+        struct xfrm_tunnel_skb_cb header;
 
         /* Copied from header for IPv4, always set to zero and DF for IPv6. */
         __be16 id;
@@ -665,10 +673,7 @@ struct xfrm_mode_skb_cb {
  * related information.
  */
 struct xfrm_spi_skb_cb {
-        union {
-                struct inet_skb_parm h4;
-                struct inet6_skb_parm h6;
-        } header;
+        struct xfrm_tunnel_skb_cb header;
 
         unsigned int daddroff;
         unsigned int family;
@@ -1510,6 +1515,7 @@ int xfrm4_rcv(struct sk_buff *skb);
 
 static inline int xfrm4_rcv_spi(struct sk_buff *skb, int nexthdr, __be32 spi)
 {
+        XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = NULL;
         XFRM_SPI_SKB_CB(skb)->family = AF_INET;
         XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
         return xfrm_input(skb, nexthdr, spi, 0);
@@ -1781,4 +1787,24 @@ static inline int xfrm_rcv_cb(struct sk_buff *skb, unsigned int family,
         return 0;
 }
 
+static inline int xfrm_tunnel_check(struct sk_buff *skb, struct xfrm_state *x,
+                                    unsigned int family)
+{
+        bool tunnel = false;
+
+        switch(family) {
+        case AF_INET:
+                if (XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4)
+                        tunnel = true;
+                break;
+        case AF_INET6:
+                if (XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip6)
+                        tunnel = true;
+                break;
+        }
+        if (tunnel && !(x->outer_mode->flags & XFRM_MODE_FLAG_TUNNEL))
+                return -EINVAL;
+
+        return 0;
+}
 #endif  /* _NET_XFRM_H */
diff --git a/net/ipv4/xfrm4_protocol.c b/net/ipv4/xfrm4_protocol.c
index 862a26c2014f..cdc09efca442 100644
--- a/net/ipv4/xfrm4_protocol.c
+++ b/net/ipv4/xfrm4_protocol.c
@@ -65,6 +65,7 @@ int xfrm4_rcv_encap(struct sk_buff *skb, int nexthdr, __be32 spi,
         int ret;
         struct xfrm4_protocol *handler;
 
+        XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = NULL;
         XFRM_SPI_SKB_CB(skb)->family = AF_INET;
         XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
 
@@ -84,6 +85,8 @@ static int xfrm4_esp_rcv(struct sk_buff *skb)
         int ret;
         struct xfrm4_protocol *handler;
 
+        XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = NULL;
+
         for_each_protocol_rcu(esp4_handlers, handler)
                 if ((ret = handler->handler(skb)) != -EINVAL)
                         return ret;
@@ -108,6 +111,8 @@ static int xfrm4_ah_rcv(struct sk_buff *skb)
         int ret;
         struct xfrm4_protocol *handler;
 
+        XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = NULL;
+
         for_each_protocol_rcu(ah4_handlers, handler)
                 if ((ret = handler->handler(skb)) != -EINVAL)
                         return ret;;
@@ -132,6 +137,8 @@ static int xfrm4_ipcomp_rcv(struct sk_buff *skb)
         int ret;
         struct xfrm4_protocol *handler;
 
+        XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = NULL;
+
         for_each_protocol_rcu(ipcomp4_handlers, handler)
                 if ((ret = handler->handler(skb)) != -EINVAL)
                         return ret;
diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c
index 99e3a9e5285e..4218164f4f5e 100644
--- a/net/xfrm/xfrm_input.c
+++ b/net/xfrm/xfrm_input.c
@@ -163,6 +163,11 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 
                 skb->sp->xvec[skb->sp->len++] = x;
 
+                if (xfrm_tunnel_check(skb, x, family)) {
+                        XFRM_INC_STATS(net, LINUX_MIB_XFRMINSTATEMODEERROR);
+                        goto drop;
+                }
+
                 spin_lock(&x->lock);
                 if (unlikely(x->km.state == XFRM_STATE_ACQ)) {
                         XFRM_INC_STATS(net, LINUX_MIB_XFRMACQUIREERROR);