[PATCH] xfrm: check bundle policy existance before dereferencing it

["Timo Teräs" <timo.teras@iki.fi>]

Fix the bundle validation code to not assume having a valid policy.
When we have multiple transformations for a xfrm policy, the bundle
instance will be a chain of bundles with only the first one having
the policy reference. When policy_genid is bumped it will expire the
first bundle in the chain which is equivalent of expiring the whole
chain.

Reported-bisected-and-tested-by: Justin P. Mattock <justinmattock@gmail.com>
Signed-off-by: Timo Teräs <timo.teras@iki.fi>
---
 net/xfrm/xfrm_policy.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 4bf27d9..af1c173 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -2300,7 +2300,8 @@ int xfrm_bundle_ok(struct xfrm_policy *pol, struct xfrm_dst *first,
 			return 0;
 		if (xdst->xfrm_genid != dst->xfrm->genid)
 			return 0;
-		if (xdst->policy_genid != atomic_read(&xdst->pols[0]->genid))
+		if (xdst->num_pols > 0 &&
+		    xdst->policy_genid != atomic_read(&xdst->pols[0]->genid))
 			return 0;
 
 		if (strict && fl &&
-- 
1.7.0.4