[PATCH ipsec] xfrm: fix dflt policy check when there is no policy configured

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: 2d151d39073a ("xfrm: Add possibility to set the default to block if we have no policy")
Signed-off-by: Nicolas Dichtel <redacted>
---
 include/net/xfrm.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 2308210793a0..55e574511af5 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h

@@ -1162,7 +1162,7 @@ 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);

-- 
2.33.0

Hi Nicolas,

On Mon, Nov 22, 2021 at 11:33:13 +0100, Nicolas Dichtel wrote:

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).

How can I reproduce this? 
I tried adding fwd block and no policy and that blocked the forwarded traffic.
I ran into another issue with fwd block and and tunnel. I will double check. Next week.

Le 25/11/2021 à 07:57, Antony Antony a écrit :

Hi Nicolas,

Hi Antony,

On Mon, Nov 22, 2021 at 11:33:13 +0100, Nicolas Dichtel wrote:

quoted

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).

How can I reproduce this? 
I tried adding fwd block and no policy and that blocked the forwarded traffic.
I ran into another issue with fwd block and and tunnel. I will double check. Next week.

With the out default policy set to 'block' and no out policy configured, the
packets are forwarded. After my patch, packets are blocked:

$ ip xfrm policy getdefault
Default policies:
 in:  accept
 fwd: accept
 out: block
$ ip xfrm policy
$


Regards,
Nicolas

On Mon, Nov 22, 2021 at 11:33:13AM +0100, Nicolas Dichtel wrote:

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: 2d151d39073a ("xfrm: Add possibility to set the default to block if we have no policy")
Signed-off-by: Nicolas Dichtel <redacted>

Applied, thanks Nicolas!