[Patch net] net: check dead netns for peernet2id_alloc()

[Patch net] net: check dead netns for peernet2id_alloc()

[Cong Wang]

Andrei reports we still allocate netns ID from idr after we destroy
it in cleanup_net().

cleanup_net():
  ...
  idr_destroy(&net->netns_ids);
  ...
  list_for_each_entry_reverse(ops, &pernet_list, list)
    ops_exit_list(ops, &net_exit_list);
      -> rollback_registered_many()
        -> rtmsg_ifinfo_build_skb()
         -> rtnl_fill_ifinfo()
           -> peernet2id_alloc()

After that point we should not even access net->netns_ids, we
should check the death of the current netns as early as we can in
peernet2id_alloc().

For net-next we can consider to avoid sending rtmsg totally,
it is a good optimization for netns teardown path.

Fixes: 0c7aecd4bde4 ("netns: add rtnl cmd to add and get peer netns ids")
Reported-by: Andrei Vagin <avagin@gmail.com>
Cc: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
---
 net/core/net_namespace.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index f61c0e0..7001da9 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -219,6 +219,8 @@ int peernet2id_alloc(struct net *net, struct net *peer)
 	bool alloc;
 	int id;
 
+	if (atomic_read(&net->count) == 0)
+		return NETNSA_NSID_NOT_ASSIGNED;
 	spin_lock_irqsave(&net->nsid_lock, flags);
 	alloc = atomic_read(&peer->count) == 0 ? false : true;
 	id = __peernet2id_alloc(net, peer, &alloc);
-- 
2.1.0

Re: [Patch net] net: check dead netns for peernet2id_alloc()

[Andrei Vagin]

On Wed, Nov 16, 2016 at 10:27 AM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
> Andrei reports we still allocate netns ID from idr after we destroy
> it in cleanup_net().
>
> cleanup_net():
>   ...
>   idr_destroy(&net->netns_ids);
>   ...
>   list_for_each_entry_reverse(ops, &pernet_list, list)
>     ops_exit_list(ops, &net_exit_list);
>       -> rollback_registered_many()
>         -> rtmsg_ifinfo_build_skb()
>          -> rtnl_fill_ifinfo()
>            -> peernet2id_alloc()
>
> After that point we should not even access net->netns_ids, we
> should check the death of the current netns as early as we can in
> peernet2id_alloc().
>
> For net-next we can consider to avoid sending rtmsg totally,
> it is a good optimization for netns teardown path.

It works for me and looks good. Thanks.

Acked-by: Andrei Vagin <avagin@openvz.org>

>
> Fixes: 0c7aecd4bde4 ("netns: add rtnl cmd to add and get peer netns ids")
> Reported-by: Andrei Vagin <avagin@gmail.com>
> Cc: Nicolas Dichtel <nicolas.dichtel@6wind.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
> ---
>  net/core/net_namespace.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index f61c0e0..7001da9 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -219,6 +219,8 @@ int peernet2id_alloc(struct net *net, struct net *peer)
>         bool alloc;
>         int id;
>
> +       if (atomic_read(&net->count) == 0)
> +               return NETNSA_NSID_NOT_ASSIGNED;
>         spin_lock_irqsave(&net->nsid_lock, flags);
>         alloc = atomic_read(&peer->count) == 0 ? false : true;
>         id = __peernet2id_alloc(net, peer, &alloc);
> --
> 2.1.0
>

Re: [Patch net] net: check dead netns for peernet2id_alloc()

[Nicolas Dichtel]

Le 16/11/2016 à 19:27, Cong Wang a écrit :
> Andrei reports we still allocate netns ID from idr after we destroy
> it in cleanup_net().
> 
> cleanup_net():
>   ...
>   idr_destroy(&net->netns_ids);
>   ...
>   list_for_each_entry_reverse(ops, &pernet_list, list)
>     ops_exit_list(ops, &net_exit_list);
>       -> rollback_registered_many()
>         -> rtmsg_ifinfo_build_skb()
>          -> rtnl_fill_ifinfo()
>            -> peernet2id_alloc()
> 
> After that point we should not even access net->netns_ids, we
> should check the death of the current netns as early as we can in
> peernet2id_alloc().
> 
> For net-next we can consider to avoid sending rtmsg totally,
> it is a good optimization for netns teardown path.
> 
> Fixes: 0c7aecd4bde4 ("netns: add rtnl cmd to add and get peer netns ids")
> Reported-by: Andrei Vagin <avagin@gmail.com>
> Cc: Nicolas Dichtel <nicolas.dichtel@6wind.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>

Re: [Patch net] net: check dead netns for peernet2id_alloc()

[David Miller]

From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Wed, 16 Nov 2016 10:27:02 -0800

> Andrei reports we still allocate netns ID from idr after we destroy
> it in cleanup_net().
> 
> cleanup_net():
>   ...
>   idr_destroy(&net->netns_ids);
>   ...
>   list_for_each_entry_reverse(ops, &pernet_list, list)
>     ops_exit_list(ops, &net_exit_list);
>       -> rollback_registered_many()
>         -> rtmsg_ifinfo_build_skb()
>          -> rtnl_fill_ifinfo()
>            -> peernet2id_alloc()
> 
> After that point we should not even access net->netns_ids, we
> should check the death of the current netns as early as we can in
> peernet2id_alloc().
> 
> For net-next we can consider to avoid sending rtmsg totally,
> it is a good optimization for netns teardown path.
> 
> Fixes: 0c7aecd4bde4 ("netns: add rtnl cmd to add and get peer netns ids")
> Reported-by: Andrei Vagin <avagin@gmail.com>
> Cc: Nicolas Dichtel <nicolas.dichtel@6wind.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>

Applied and queued up for -stable, thanks.