netdev - Re: netns: use a spin_lock to protect nsid management

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Message-ID: <CAM_iQpUSgpeL_Dy+U+KrBd=h3bhm03vASupdO-9dSs+CKYjNeg@mail.gmail.com>
Date:	Tue, 12 May 2015 12:16:30 -0700
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>
Cc:	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	kernel-janitors@...r.kernel.org,
	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: netns: use a spin_lock to protect nsid management

(Please always Cc netdev for networking bugs)

On Tue, May 12, 2015 at 10:52 AM, Dan Carpenter
<dan.carpenter@...cle.com> wrote:
> Hello Nicolas Dichtel,
>
> The patch 95f38411df05: "netns: use a spin_lock to protect nsid
> management" from May 7, 2015, leads to the following static checker
> warning:
>
>         net/core/net_namespace.c:580 rtnl_net_newid()
>         warn: inconsistent returns 'spin_lock:&nsid_lock'.
>
> net/core/net_namespace.c
>    565
>    566          spin_lock_irqsave(&nsid_lock, flags);
>    567          if (__peernet2id(net, peer) >= 0) {
>    568                  err = -EEXIST;
>    569                  goto out;
>
> I don't know if __peernet2id() unlocks on error but it can't possibly
> restore flags so this isn't right.
>

Yes it is a bug.

Also why do we have to disable IRQ when holding the spinlock?
IOW, which case takes the spin lock in IRQ context?

Thanks.
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