xfrm: Refcount destination entry on xfrm_lookup

We return a destination entry without refcount if a socket policy is found in xfrm_lookup. This triggers a warning on a negative refcount when freeeing this dst entry. So take a refcount in this case to fix it.

This refcount was forgotten when xfrm changed to cache bundles instead of policies for outgoing flows.

Signed-off-by Steffen Klassert <[email protected]>

---
 net/xfrm/xfrm_policy.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

net/xfrm/xfrm_policy.c +2 -0

index 027e3c6..15792d8 100644
@@ -1804,6 +1804,8 @@ restart:
 				goto no_transform;
 			}
 
+			dst_hold(&xdst->u.dst);
+
 			spin_lock_bh(&xfrm_policy_sk_bundle_lock);
 			xdst->u.dst.next = xfrm_policy_sk_bundles;
 			xfrm_policy_sk_bundles = &xdst->u.dst;

Quoted 8 lines

We return a destination entry without refcount if a socket policy is found in xfrm_lookup. This triggers a warning on a negative refcount when freeeing this dst entry. So take a refcount in this case to fix it.

This refcount was forgotten when xfrm changed to cache bundles instead of policies for outgoing flows.

Quoted 1 line

Signed-off-by Steffen Klassert <[email protected]>

Acked-by Timo Teräs <[email protected]>

Ok. This is one of the corner cases I did not test: having socket policy something else than no action. I just didn't have the application ready for it. Sorry about the bug. And good catch Steffen.