[PATCH NETFILTER v2] netfilter: gre: nf_ct_gre_keymap_flush() removal

[PATCH NETFILTER v2] netfilter: gre: nf_ct_gre_keymap_flush() removal

[Vasily Averin]

nf_ct_gre_keymap_flush() is useless.
It is called from nf_conntrack_cleanup_net_list() only and tries to remove
nf_ct_gre_keymap entries from pernet gre keymap list. Though:
a) at this point the list should already be empty, all its entries were
deleted during the conntracks cleanup, because
nf_conntrack_cleanup_net_list() executes nf_ct_iterate_cleanup(kill_all)
before nf_conntrack_proto_pernet_fini():
 nf_conntrack_cleanup_net_list
  +- nf_ct_iterate_cleanup
  |   nf_ct_put
  |    nf_conntrack_put
  |     nf_conntrack_destroy
  |      destroy_conntrack
  |       destroy_gre_conntrack
  |        nf_ct_gre_keymap_destroy
  `- nf_conntrack_proto_pernet_fini
      nf_ct_gre_keymap_flush

b) Let's say we find that the keymap list is not empty. This means netns
still has a conntrack associated with gre, in which case we should not free
its memory, because this will lead to a double free and related crashes.
However I doubt it could have gone unnoticed for years, obviously
this does not happen in real life. So I think we can remove
both nf_ct_gre_keymap_flush() and nf_conntrack_proto_pernet_fini().

Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Acked-by: Florian Westphal <fw@strlen.de>
---
v2: resent, original letter was graylisted

 include/net/netfilter/nf_conntrack_core.h |  1 -
 net/netfilter/nf_conntrack_core.c         |  1 -
 net/netfilter/nf_conntrack_proto.c        |  7 -------
 net/netfilter/nf_conntrack_proto_gre.c    | 13 -------------
 4 files changed, 22 deletions(-)

diff --git a/include/net/netfilter/nf_conntrack_core.h b/include/net/netfilter/nf_conntrack_core.h
index 09f2efea0b97..13807ea94cd2 100644
--- a/include/net/netfilter/nf_conntrack_core.h
+++ b/include/net/netfilter/nf_conntrack_core.h
@@ -30,7 +30,6 @@ void nf_conntrack_cleanup_net(struct net *net);
 void nf_conntrack_cleanup_net_list(struct list_head *net_exit_list);
 
 void nf_conntrack_proto_pernet_init(struct net *net);
-void nf_conntrack_proto_pernet_fini(struct net *net);
 
 int nf_conntrack_proto_init(void);
 void nf_conntrack_proto_fini(void);
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index e0befcf8113a..ad53666120e9 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -2461,7 +2461,6 @@ void nf_conntrack_cleanup_net_list(struct list_head *net_exit_list)
 	}
 
 	list_for_each_entry(net, net_exit_list, exit_list) {
-		nf_conntrack_proto_pernet_fini(net);
 		nf_conntrack_ecache_pernet_fini(net);
 		nf_conntrack_expect_pernet_fini(net);
 		free_percpu(net->ct.stat);
diff --git a/net/netfilter/nf_conntrack_proto.c b/net/netfilter/nf_conntrack_proto.c
index 89e5bac384d7..2ca25aaad032 100644
--- a/net/netfilter/nf_conntrack_proto.c
+++ b/net/netfilter/nf_conntrack_proto.c
@@ -697,13 +697,6 @@ void nf_conntrack_proto_pernet_init(struct net *net)
 #endif
 }
 
-void nf_conntrack_proto_pernet_fini(struct net *net)
-{
-#ifdef CONFIG_NF_CT_PROTO_GRE
-	nf_ct_gre_keymap_flush(net);
-#endif
-}
-
 module_param_call(hashsize, nf_conntrack_set_hashsize, param_get_uint,
 		  &nf_conntrack_htable_size, 0600);
 
diff --git a/net/netfilter/nf_conntrack_proto_gre.c b/net/netfilter/nf_conntrack_proto_gre.c
index db11e403d818..728eeb0aea87 100644
--- a/net/netfilter/nf_conntrack_proto_gre.c
+++ b/net/netfilter/nf_conntrack_proto_gre.c
@@ -55,19 +55,6 @@ static inline struct nf_gre_net *gre_pernet(struct net *net)
 	return &net->ct.nf_ct_proto.gre;
 }
 
-void nf_ct_gre_keymap_flush(struct net *net)
-{
-	struct nf_gre_net *net_gre = gre_pernet(net);
-	struct nf_ct_gre_keymap *km, *tmp;
-
-	spin_lock_bh(&keymap_lock);
-	list_for_each_entry_safe(km, tmp, &net_gre->keymap_list, list) {
-		list_del_rcu(&km->list);
-		kfree_rcu(km, rcu);
-	}
-	spin_unlock_bh(&keymap_lock);
-}
-
 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
 				const struct nf_conntrack_tuple *t)
 {
-- 
2.25.1

Re: [PATCH NETFILTER v2] netfilter: gre: nf_ct_gre_keymap_flush() removal

[Pablo Neira Ayuso]

On Thu, Jul 01, 2021 at 08:02:24AM +0300, Vasily Averin wrote:
> nf_ct_gre_keymap_flush() is useless.
> It is called from nf_conntrack_cleanup_net_list() only and tries to remove
> nf_ct_gre_keymap entries from pernet gre keymap list. Though:
> a) at this point the list should already be empty, all its entries were
> deleted during the conntracks cleanup, because
> nf_conntrack_cleanup_net_list() executes nf_ct_iterate_cleanup(kill_all)
> before nf_conntrack_proto_pernet_fini():
>  nf_conntrack_cleanup_net_list
>   +- nf_ct_iterate_cleanup
>   |   nf_ct_put
>   |    nf_conntrack_put
>   |     nf_conntrack_destroy
>   |      destroy_conntrack
>   |       destroy_gre_conntrack
>   |        nf_ct_gre_keymap_destroy
>   `- nf_conntrack_proto_pernet_fini
>       nf_ct_gre_keymap_flush
> 
> b) Let's say we find that the keymap list is not empty. This means netns
> still has a conntrack associated with gre, in which case we should not free
> its memory, because this will lead to a double free and related crashes.
> However I doubt it could have gone unnoticed for years, obviously
> this does not happen in real life. So I think we can remove
> both nf_ct_gre_keymap_flush() and nf_conntrack_proto_pernet_fini().

Also applied.

I think nf_ct_gre_keymap_flush() became useless when the GRE was
de-modularized (built-in into nf_conntrack).