[IPSEC]: Store xfrm states in security path directly

As it is xfrm_input first collects a list of xfrm states on the stack
before storing them in the packet's security path just before it
returns.  For async crypto, this construction presents an obstacle
since we may need to leave the loop after each transform.

In fact, it's much easier to just skip the stack completely and always
store to the security path.  This is proven by the fact that this
patch actually shrinks the code.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/xfrm/xfrm_input.c

@@ -100,19 +100,29 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 {
 	int err;
 	__be32 seq;
-	struct xfrm_state *xfrm_vec[XFRM_MAX_DEPTH];
 	struct xfrm_state *x;
-	int xfrm_nr = 0;
 	int decaps = 0;
 	unsigned int nhoff = XFRM_SPI_SKB_CB(skb)->nhoff;
 	unsigned int daddroff = XFRM_SPI_SKB_CB(skb)->daddroff;
 
+	/* Allocate new secpath or COW existing one. */
+	if (!skb->sp || atomic_read(&skb->sp->refcnt) != 1) {
+		struct sec_path *sp;
+
+		sp = secpath_dup(skb->sp);
+		if (!sp)
+			goto drop;
+		if (skb->sp)
+			secpath_put(skb->sp);
+		skb->sp = sp;
+	}
+
 	seq = 0;
 	if (!spi && (err = xfrm_parse_spi(skb, nexthdr, &spi, &seq)) != 0)
 		goto drop;
 
 	do {
-		if (xfrm_nr == XFRM_MAX_DEPTH)
+		if (skb->sp->len == XFRM_MAX_DEPTH)
 			goto drop;
 
 		x = xfrm_state_lookup((xfrm_address_t *)
@@ -121,6 +131,8 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 		if (x == NULL)
 			goto drop;
 
+		skb->sp->xvec[skb->sp->len++] = x;
+
 		spin_lock(&x->lock);
 		if (unlikely(x->km.state != XFRM_STATE_VALID))
 			goto drop_unlock;
@@ -151,8 +163,6 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 
 		spin_unlock(&x->lock);
 
-		xfrm_vec[xfrm_nr++] = x;
-
 		if (x->inner_mode->input(x, skb))
 			goto drop;
 
@@ -166,24 +176,6 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 			goto drop;
 	} while (!err);
 
-	/* Allocate new secpath or COW existing one. */
-
-	if (!skb->sp || atomic_read(&skb->sp->refcnt) != 1) {
-		struct sec_path *sp;
-		sp = secpath_dup(skb->sp);
-		if (!sp)
-			goto drop;
-		if (skb->sp)
-			secpath_put(skb->sp);
-		skb->sp = sp;
-	}
-	if (xfrm_nr + skb->sp->len > XFRM_MAX_DEPTH)
-		goto drop;
-
-	memcpy(skb->sp->xvec + skb->sp->len, xfrm_vec,
-	       xfrm_nr * sizeof(xfrm_vec[0]));
-	skb->sp->len += xfrm_nr;
-
 	nf_reset(skb);
 
 	if (decaps) {
@@ -197,11 +189,7 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 
 drop_unlock:
 	spin_unlock(&x->lock);
-	xfrm_state_put(x);
 drop:
-	while (--xfrm_nr >= 0)
-		xfrm_state_put(xfrm_vec[xfrm_nr]);
-
 	kfree_skb(skb);
 	return 0;
 }