netfilter: nf_conntrack: fix early_drop with reliable event delivery

If reliable event delivery is enabled and ctnetlink fails to deliver
the destroy event in early_drop, the conntrack subsystem cannot
drop any the candidate flow that was planned to be evicted.

Reported-by: Kerin Millar <kerframil@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 2 deletions

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index ed86a3be678e..fa4b82c8ae80 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -635,8 +635,12 @@ static noinline int early_drop(struct net *net, unsigned int hash)
 
         if (del_timer(&ct->timeout)) {
                 death_by_timeout((unsigned long)ct);
-                dropped = 1;
-                NF_CT_STAT_INC_ATOMIC(net, early_drop);
+                /* Check if we indeed killed this entry. Reliable event
+                   delivery may have inserted it into the dying list. */
+                if (test_bit(IPS_DYING_BIT, &ct->status)) {
+                        dropped = 1;
+                        NF_CT_STAT_INC_ATOMIC(net, early_drop);
+                }
         }
         nf_ct_put(ct);
         return dropped;