From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH RFC] tun: add ioctl to modify vnet header size Date: Thu, 18 Mar 2010 00:11:17 +0200 Message-ID: <20100317221117.GA7541@redhat.com> References: <20100317213504.GA7433@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "David S. Miller" , David Woodhouse , Herbert Xu , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, netdev-owner@vger.kernel.org, Paul Moore , sri@linux.vnet.ibm.com To: David Stevens Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wed, Mar 17, 2010 at 03:02:44PM -0700, David Stevens wrote: > netdev-owner@vger.kernel.org wrote on 03/17/2010 02:35:04 PM: > > > On Wed, Mar 17, 2010 at 02:10:11PM -0700, David Stevens wrote: > > > Shouldn't we enforce a maximum too? Esp. if overflow/underflow > > > will break any of the checks when it's used. > > > > > > +-DLS > > > > So the maximum is MAX_INT :) > > I don't think it can break any checks that aren't > > already broken - what do you have in mind? > > I was thinking more like a page. At least, it'd be better > to fail when trying to set it large than failing allocations > later. As a header, it really ought to be small. > But if it works, or fails gracefully, at 2^31-1 on 32-bit > machines, negative values, etc, then it's ok. Just a suggestion. > > +-DLS All this does is set how much of the buffer to skip, this option does not allocate any memory. So if you set it to a value > length that you passed in, you get -EINVAL. Anything else should work. Negative values are checked for and return -EINVAL when you try to set it. At least, all that's by design - pls take a look at the code and if you see any issues, speak up please. I agree we don't really need to support very large values here, it just seemed less work. -- MST