[XFRM]: Fix policy update bug when increasing priority of last policy.

Based upon a patch by Patrick McHardy.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/xfrm/xfrm_policy.c

@@ -332,7 +332,7 @@ int xfrm_policy_insert(int dir, struct xfrm_policy *policy, int excl)
 	struct xfrm_policy **newpos = NULL;
 
 	write_lock_bh(&xfrm_policy_lock);
-	for (p = &xfrm_policy_list[dir]; (pol=*p)!=NULL; p = &pol->next) {
+	for (p = &xfrm_policy_list[dir]; (pol=*p)!=NULL;) {
 		if (!delpol && memcmp(&policy->selector, &pol->selector, sizeof(pol->selector)) == 0) {
 			if (excl) {
 				write_unlock_bh(&xfrm_policy_lock);
@@ -342,8 +342,10 @@ int xfrm_policy_insert(int dir, struct xfrm_policy *policy, int excl)
 			delpol = pol;
 			if (policy->priority > pol->priority)
 				continue;
-		} else if (policy->priority >= pol->priority)
+		} else if (policy->priority >= pol->priority) {
+			p = &pol->next;
 			continue;
+		}
 		if (!newpos)
 			newpos = p;
 		if (delpol)