xfrm: Fix unlink race when policies are deleted.

When a policy is unlinked from the lists in thread context,
the xfrm timer can fire before we can mark this policy as dead.
So reinitialize the bydst hlist, then hlist_unhashed() will
notice that this policy is not linked and will avoid a
doulble unlink of that policy.

Reported-by: Xianpeng Zhao <673321875@qq.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 4b98b25793c5..1d5c7bf29938 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -1158,7 +1158,7 @@ static struct xfrm_policy *__xfrm_policy_unlink(struct xfrm_policy *pol,
         if (hlist_unhashed(&pol->bydst))
                 return NULL;
 
-        hlist_del(&pol->bydst);
+        hlist_del_init(&pol->bydst);
         hlist_del(&pol->byidx);
         list_del(&pol->walk.all);
         net->xfrm.policy_count[dir]--;