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Date:   Fri, 28 Oct 2022 11:17:05 +0200
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Neal Liu <neal_liu@aspeedtech.com>
Cc:     Lei Yu <yulei.sh@bytedance.com>, Felipe Balbi <balbi@kernel.org>,
        Joel Stanley <joel@jms.id.au>,
        Andrew Jeffery <andrew@aj.id.au>,
        Henry Tian <tianxiaofeng@bytedance.com>,
        Jakob Koschel <jakobkoschel@gmail.com>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-aspeed@lists.ozlabs.org" <linux-aspeed@lists.ozlabs.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Ryan Chen <ryan_chen@aspeedtech.com>
Subject: Re: [PATCH] usb: gadget: aspeed: fix buffer overflow
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On Fri, Oct 28, 2022 at 09:04:52AM +0000, Neal Liu wrote:
> > > Thanks for your feedback.
> > > I tried to reproduce it on my side, and it cannot be reproduce it.
> > > Here are my test sequences:
> > > 1. emulate one of the vhub port to usb ethernet through Linux gadget
> > > (ncm)
> > 
> > We are using rndis instead of ncm.
> > 
> > > 2. connect BMC vhub to Host
> > > 3. BMC & Host can ping each other (both usb eth dev default mtu is
> > > 1500) 4. Set BMC mtu to 1000 (Host OS cannot set usb eth dev mtu to
> > > 2000, it's maxmtu is 1500)
> > 
> > Not sure if it's related, but in my case (USB rndis, Debian 10 OS) it should be
> > able to set MTU to 2000.
> 
> Using rndis is able to set MTU to 2000, and the issue can be reproduced.

Please NEVER use rndis anymore.  I need to go just delete that driver
from the tree.

It is insecure-by-design and will cause any system that runs it to be
instantly compromised and it can not be fixed.  Never trust it.

Even for data throughput tests, I wouldn't trust it as it does odd
things with packet sizes as you show here.

thanks,

greg k-h