From: ebiederm@xmission•com (Eric W. Biederman)
To: Nathan Lynch <ntl@pobox•com>
Cc: linux-arch@vger•kernel.org, linux-kernel@vger•kernel.org,
netdev@vger•kernel.org, linux-fsdevel@vger•kernel.org,
jamal <hadi@cyberus•ca>, Daniel Lezcano <daniel.lezcano@free•fr>,
Linux Containers <containers@lists•osdl.org>,
Renato Westphal <renatowestphal@gmail•com>
Subject: Re: [PATCH 3/7] ns proc: Add support for the network namespace.
Date: Wed, 11 May 2011 14:34:37 -0700 [thread overview]
Message-ID: <m139kkncpe.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <1305141705.1236.49.camel@orca.stoopid.dyndns.org> (Nathan Lynch's message of "Wed, 11 May 2011 14:21:34 -0500")
Nathan Lynch <ntl@pobox•com> writes:
> On Fri, 2011-05-06 at 19:24 -0700, Eric W. Biederman wrote:
>> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
>> index 3f86026..bf7707e 100644
>> --- a/net/core/net_namespace.c
>> +++ b/net/core/net_namespace.c
>> @@ -573,3 +573,34 @@ 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);
>
> This should use task_nsproxy() and check the result before grabbing the
> net_ns, but I think you fix that in a later patch.
>
> Regardless, it looks as if all the proc_ns_ops->get() implementations
> really just want the nsproxy, so maybe the get() methods should take
> that instead of the task_struct, and proc_ns_instantiate() should do
> something like:
>
> struct nsproxy *nsproxy;
> ...
>
> ei->ns_ops = ns_ops;
> error = -ESRCH;
> rcu_read_lock();
> nsproxy = task_nsproxy(task);
> rcu_read_unlock();
> if (!nsproxy)
> got out;
> ei->ns = ns_ops->get(nsproxy);
>
>
> So then the zombie check is consolidated in one place instead of having
> to do it in every get() method.
For the pid namespace at least I want the task not the nsproxy,
so I can use task_active_pid_namespace().
I admit that is a little asymmetrical with the install, but at
least until the details of getting the pid namespace working in
this context are worked out I don't want to reconsider the
current design.
There is also the user namespace that does not even exist in
nsproxy to consider. I will worry about that namespace when
it happens.
Ultimately nsproxy is an space/time optimization that not all
namespaces use so forcing it in the design is probably not
what we want.
>> + rcu_read_unlock();
>> + return net;
>> +}
>> +
>> +static void netns_put(void *ns)
>> +{
>> + put_net(ns);
>> +}
>> +
>> +static int netns_install(struct nsproxy *nsproxy, void *ns)
>> +{
>> + put_net(nsproxy->net_ns);
>> + nsproxy->net_ns = get_net(ns);
>> + return 0;
>> +}
>
> This introduces a window where, potentially, nsproxy->net_ns is stale
> before it is updated with the namespace which is being attached, no?
> (Same concern applies to other install methods in the patch set). It
> seems possible to oops the kernel in this window by looking up
> /proc/$PID/ns/net while $PID is in the midst of setns().
Except the nsproxy being referred to is a brand new nsproxy, with an
extra reference count on every namespace. current->nsproxy still
contains the reference counts of the current process.
Eric
next prev parent reply other threads:[~2011-05-11 21:34 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-07 2:23 [PATCH 0/7] Network namespace manipulation with file descriptors Eric W. Biederman
2011-05-07 2:24 ` [PATCH 1/7] ns: proc files for namespace naming policy Eric W. Biederman
[not found] ` <1304735101-1824-1-git-send-email-ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2011-05-07 2:24 ` [PATCH 2/7] ns: Introduce the setns syscall Eric W. Biederman
[not found] ` <1304735101-1824-2-git-send-email-ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2011-05-07 8:01 ` Rémi Denis-Courmont
2011-05-07 13:57 ` Eric W. Biederman
2011-05-07 22:39 ` Daniel Lezcano
2011-05-08 3:51 ` Matt Helsley
2011-05-11 19:21 ` Nathan Lynch
2011-05-11 20:33 ` Eric W. Biederman
2011-05-07 2:25 ` [PATCH 6/7] net: Allow setting the network namespace by fd Eric W. Biederman
2011-05-07 22:46 ` Daniel Lezcano
2011-05-07 2:24 ` [PATCH 3/7] ns proc: Add support for the network namespace Eric W. Biederman
2011-05-07 22:41 ` Daniel Lezcano
2011-05-11 19:21 ` Nathan Lynch
2011-05-11 21:34 ` Eric W. Biederman [this message]
2011-05-11 21:42 ` Nathan Lynch
2011-05-07 2:24 ` [PATCH 4/7] ns proc: Add support for the uts namespace Eric W. Biederman
2011-05-07 22:42 ` Daniel Lezcano
2011-05-07 2:24 ` [PATCH 5/7] ns proc: Add support for the ipc namespace Eric W. Biederman
2011-05-07 22:44 ` Daniel Lezcano
2011-05-07 2:25 ` [PATCH 7/7] ns: Wire up the setns system call Eric W. Biederman
2011-05-07 8:27 ` Geert Uytterhoeven
2011-05-07 14:09 ` Eric W. Biederman
2011-05-07 18:22 ` Geert Uytterhoeven
2011-05-07 13:59 ` Mike Frysinger
2011-05-07 20:06 ` James Bottomley
2011-05-08 2:19 ` Eric W. Biederman
2011-05-08 4:02 ` James Bottomley
2011-05-07 22:37 ` [PATCH 1/7] ns: proc files for namespace naming policy Daniel Lezcano
2011-05-11 19:20 ` Nathan Lynch
2011-05-11 22:52 ` Eric W. Biederman
[not found] ` <m1tyd7p7tq.fsf-+imSwln9KH6u2/kzUuoCbdi2O/JbrIOy@public.gmane.org>
2011-05-07 6:58 ` [PATCH 0/7] Network namespace manipulation with file descriptors Alex Bligh
2011-05-07 14:18 ` Eric W. Biederman
2011-05-08 12:31 ` Alex Bligh
[not found] ` <m1fwoqoapn.fsf-+imSwln9KH6u2/kzUuoCbdi2O/JbrIOy@public.gmane.org>
2011-05-17 11:11 ` David Lamparter
2011-05-17 14:33 ` Eric W. Biederman
2011-05-17 15:35 ` David Lamparter
2011-05-22 4:19 ` Renato Westphal
2011-05-09 19:04 ` David Miller
2011-05-09 19:59 ` Eric W. Biederman
2011-05-09 20:40 ` David Miller
2011-05-09 20:54 ` Eric W. Biederman
2011-05-09 20:55 ` David Miller
2011-05-10 21:56 ` Luck, Tony
2011-05-10 23:02 ` Eric W. Biederman
2011-05-18 12:43 ` Identifying network namespaces (was: Network namespace manipulation with file descriptors) David Lamparter
2011-05-18 13:03 ` Alexey Dobriyan
[not found] ` <BANLkTikmrC86hk=W84UBwhJLe_uGAN4w9w-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2011-05-18 13:33 ` David Lamparter
2011-05-18 14:13 ` Alexey Dobriyan
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