Re: [PATCH net-net 0/4] Increase the limit of tuntap queues

On Mon, Nov 24, 2014 at 11:23:05AM +0800, Jason Wang wrote:

On 11/23/2014 06:46 PM, Michael S. Tsirkin wrote:

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On Wed, Nov 19, 2014 at 10:44:27PM +0200, Michael S. Tsirkin wrote:

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On Wed, Nov 19, 2014 at 03:16:28PM -0500, David Miller wrote:

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From: Pankaj Gupta <redacted>
Date: Tue, 18 Nov 2014 21:52:54 +0530

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- Accept maximum number of queues as sysctl param so that any user space 
  application like libvirt can use this value to limit number of queues. Also
  Administrators can specify maximum number of queues by updating this sysctl
  entry.

This is the only part I don't like.

Just let whoever has privileges to configure the tun device shoot
themselves in the foot if they want to by configuring "too many"
queues.

If the virtual entity runs itself out of resources by doing something
stupid, it's purely their problem.

Well it will run host out of kernel, no?

To clarify:

At the moment attaching/detaching queues is an unpriveledged operation.

Shouldn't we worry that an application can cause large
allocations, and provide a way to limit these?

But creating new queues (TUNSETIFF) is privileged. There's no way for
unprivileged user to allocate more resources. So we are safe here?

Hmm, that's true, I think I was confused.
Thanks for setting me straight.

-- 
MST