netdev - Re: [PATCH net v2] net: nsid cannot be allocated for a dead netns

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Date:   Wed, 16 Nov 2016 09:29:29 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Nicolas Dichtel <nicolas.dichtel@...nd.com>
Cc:     Andrey Wagin <avagin@...il.com>,
        David Miller <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH net v2] net: nsid cannot be allocated for a dead netns

On Wed, Nov 16, 2016 at 1:49 AM, Nicolas Dichtel
<nicolas.dichtel@...nd.com> wrote:
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index f61c0e02a413..63f65387f4e1 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -159,6 +159,9 @@ static int alloc_netid(struct net *net, struct net *peer, int reqid)
>                 max = reqid + 1;
>         }
>
> +       if (!atomic_read(&net->count) || !atomic_read(&peer->count))
> +               return -EINVAL;
> +
>         return idr_alloc(&net->netns_ids, peer, min, max, GFP_ATOMIC);
>  }


There is already a check in peernet2id_alloc(), so why not just the following?

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);