xfrm: fix dflt policy check when there is no policy configured

[ Upstream commit ec3bb89 ]

When there is no policy configured on the system, the default policy is
checked in xfrm_route_forward. However, it was done with the wrong
direction (XFRM_POLICY_FWD instead of XFRM_POLICY_OUT).
The default policy for XFRM_POLICY_FWD was checked just before, with a call
to xfrm[46]_policy_check().

CC: stable@vger.kernel.org
Fixes: 2d151d3 ("xfrm: Add possibility to set the default to block if we have no policy")
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

include/net/xfrm.h

@@ -1175,7 +1175,7 @@ static inline int xfrm_route_forward(struct sk_buff *skb, unsigned short family)
 {
 	struct net *net = dev_net(skb->dev);
 
-	if (xfrm_default_allow(net, XFRM_POLICY_FWD))
+	if (xfrm_default_allow(net, XFRM_POLICY_OUT))
 		return !net->xfrm.policy_count[XFRM_POLICY_OUT] ||
 			(skb_dst(skb)->flags & DST_NOXFRM) ||
 			__xfrm_route_forward(skb, family);