netdev - Re: [PATCH net,v2 1/2] hv_netvsc: Fix offset usage in netvsc_send

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Date:   Thu, 21 Nov 2019 17:03:35 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Haiyang Zhang <haiyangz@...rosoft.com>
Cc:     "sashal@...nel.org" <sashal@...nel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "olaf@...fle.de" <olaf@...fle.de>, vkuznets <vkuznets@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net,v2 1/2] hv_netvsc: Fix offset usage in
 netvsc_send_table()

On Fri, 22 Nov 2019 00:54:20 +0000, Haiyang Zhang wrote:
> > >
> > > -	tab = (u32 *)((unsigned long)&nvmsg->msg.v5_msg.send_table +
> > > -		      nvmsg->msg.v5_msg.send_table.offset);
> > > +	if (offset > msglen - count * sizeof(u32)) {  
> > 
> > Can't this underflow now? What if msglen is small?  
> msglen came from the vmbus container message. We trust it to be big
> enough for the data region.

Ok, it looked like it was read from some descriptor which could
potentially be controlled by "the other side" but I trust your
judgement :)

Both patches LGTM, then.