Messages in this thread | | | From | (Eric W. Biederman) | Date | Thu, 23 Sep 2010 09:00:31 -0700 | Subject | Re: [PATCH 3/8] ns proc: Add support for the network namespace. |
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Louis Rilling <Louis.Rilling@kerlabs.com> writes:
> On 23/09/10 1:47 -0700, Eric W. Biederman wrote: >> >> Implementing file descriptors for the network namespace is simple and >> straight forward. >> >> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> > > [...] > >> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c >> index c988e68..581a088 100644 >> --- a/net/core/net_namespace.c >> +++ b/net/core/net_namespace.c >> @@ -571,3 +571,33 @@ void unregister_pernet_device(struct pernet_operations *ops) >> mutex_unlock(&net_mutex); >> } >> EXPORT_SYMBOL_GPL(unregister_pernet_device); >> + >> +#ifdef CONFIG_NET_NS >> +static void *netns_get(struct task_struct *task) >> +{ >> + struct net *net; >> + rcu_read_lock(); >> + net = get_net(task->nsproxy->net_ns); > > task could be exiting, so task->nsproxy could be NULL, right? > Maybe make proc_ns_instantiate() rcu_dereference task->nsproxy, check for it > being not NULL, and pass task->nsproxy to ns_ops->get()?
Ugh. Thanks. fixed.
Somehow I forgot /proc shows zombies which means nsproxy will definitely be NULL in those cases. It is easy enough to handle once my brain gets out of park.
I don't hold any locks at that point so I don't think I want to do anything in proc_ns_instantiate() except handle a NULL return when the ns_ops->get() fails.
> That could be an issue for the user namespace since it is not in nsproxy, but > maybe no reasonable usage of ns_ops with user namespaces is > envisioned.
It is also a issue for the pid namespace.
> Otherwise, checking that task is alive with RCU locked in proc_ns_instantiate() should be enough to be > rely on task->cred when calling ns_ops->get().
That sounds about right. I keep conveniently forgetting the user namespace. It doesn't support unshare right now so there isn't anything I can reasonably do with it at the moment. It wouldn't surprise me if I don't wind up handling the user namespace like the pid namespace, where unsharing it changes the properties for the children and not the parent. Bleh.
Eric
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