xfrm: add RX datapath protection for IPsec packet offload mode

Traffic received by device with enabled IPsec packet offload should
be forwarded to the stack only after decryption, packet headers and
trailers removed.

Such packets are expected to be seen as normal (non-XFRM) ones, while
not-supported packets should be dropped by the HW.
Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

include/net/xfrm.h

@@ -1102,6 +1102,29 @@ xfrm_state_addr_cmp(const struct xfrm_tmpl *tmpl, const struct xfrm_state *x, un
 	return !0;
 }
 
+#ifdef CONFIG_XFRM
+static inline struct xfrm_state *xfrm_input_state(struct sk_buff *skb)
+{
+	struct sec_path *sp = skb_sec_path(skb);
+
+	return sp->xvec[sp->len - 1];
+}
+#endif
+
+static inline struct xfrm_offload *xfrm_offload(struct sk_buff *skb)
+{
+#ifdef CONFIG_XFRM
+	struct sec_path *sp = skb_sec_path(skb);
+
+	if (!sp || !sp->olen || sp->len != sp->olen)
+		return NULL;
+
+	return &sp->ovec[sp->olen - 1];
+#else
+	return NULL;
+#endif
+}
+
 #ifdef CONFIG_XFRM
 int __xfrm_policy_check(struct sock *, int dir, struct sk_buff *skb,
 			unsigned short family);
@@ -1133,10 +1156,19 @@ static inline int __xfrm_policy_check2(struct sock *sk, int dir,
 {
 	struct net *net = dev_net(skb->dev);
 	int ndir = dir | (reverse ? XFRM_POLICY_MASK + 1 : 0);
+	struct xfrm_offload *xo = xfrm_offload(skb);
+	struct xfrm_state *x;
 
 	if (sk && sk->sk_policy[XFRM_POLICY_IN])
 		return __xfrm_policy_check(sk, ndir, skb, family);
 
+	if (xo) {
+		x = xfrm_input_state(skb);
+		if (x->xso.type == XFRM_DEV_OFFLOAD_PACKET)
+			return (xo->flags & CRYPTO_DONE) &&
+			       (xo->status & CRYPTO_SUCCESS);
+	}
+
 	return __xfrm_check_nopolicy(net, skb, dir) ||
 	       __xfrm_check_dev_nopolicy(skb, dir, family) ||
 	       __xfrm_policy_check(sk, ndir, skb, family);
@@ -1872,29 +1904,6 @@ static inline void xfrm_states_delete(struct xfrm_state **states, int n)
 }
 #endif
 
-#ifdef CONFIG_XFRM
-static inline struct xfrm_state *xfrm_input_state(struct sk_buff *skb)
-{
-	struct sec_path *sp = skb_sec_path(skb);
-
-	return sp->xvec[sp->len - 1];
-}
-#endif
-
-static inline struct xfrm_offload *xfrm_offload(struct sk_buff *skb)
-{
-#ifdef CONFIG_XFRM
-	struct sec_path *sp = skb_sec_path(skb);
-
-	if (!sp || !sp->olen || sp->len != sp->olen)
-		return NULL;
-
-	return &sp->ovec[sp->olen - 1];
-#else
-	return NULL;
-#endif
-}
-
 void __init xfrm_dev_init(void);
 
 #ifdef CONFIG_XFRM_OFFLOAD