Re: [PATCH] namespace:unmount pid_namespace's proc_mnt when copy_net_ns failed

Gao feng
2012-11-02T07:33:31Z

于 2012年11月02日 15:02, Eric W. Biederman 写道:
> Gao feng <gaofeng@cn.fujitsu.com> writes:
>
>> we should call pid_ns_release_proc to unmount pid_namespace's
>> proc_mnt when copy_net_ns failed in function create_new_namespaces.
>>
>> otherwise,the proc_mnt will not be freed and because the super_block
>> of proc_mnt also add the reference of the pid_namespace,so this
>> pid_namespace will never be released too.
>
> Ouch!
>
> Have you encountered this failure in practice or is this just from
> review?

I add some printk in pid_ns_release_proc,it's not called in above case.
when copy_net_ns failed,this pid_namespace is not used by any task,
so proc_flush_task can't call pid_ns_release_proc to umount this pidns->proc_mnt.
it's the only chance we can unmount this pindns->proc_mnt.

With this patch,everything runs well.

Thanks
Gao

>
> I'm trying to gauge the severity of this leak.
>
> Eric
>
>
>> Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
>> ---
>> kernel/nsproxy.c | 5 ++++-
>> 1 files changed, 4 insertions(+), 1 deletions(-)
>>
>> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
>> index b576f7f..d536480 100644
>> --- a/kernel/nsproxy.c
>> +++ b/kernel/nsproxy.c
>> @@ -99,8 +99,11 @@ static struct nsproxy *create_new_namespaces(unsigned long flags,
>> return new_nsp;
>>
>> out_net:
>> - if (new_nsp->pid_ns)
>> + if (new_nsp->pid_ns) {
>> + if (flags & CLONE_NEWPID)
>> + pid_ns_release_proc(new_nsp->pid_ns);
>> put_pid_ns(new_nsp->pid_ns);
>> + }
>> out_pid:
>> if (new_nsp->ipc_ns)
>> put_ipc_ns(new_nsp->ipc_ns);
> --
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