netdev - Re: [PATCH RFC] net: Validate size of non-TSO packets in validate_xmit

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Message-ID: <CACKFLim51U_NGEU9nH5ZPWiup==aDLQM+x3p_O0-3EerZQ74hg@mail.gmail.com>
Date:   Tue, 26 Feb 2019 10:22:42 -0800
From:   Michael Chan <michael.chan@...adcom.com>
To:     David Miller <davem@...emloft.net>
Cc:     Mahesh Bandewar (महेश बंडेवार) 
        <maheshb@...gle.com>, Eric Dumazet <edumazet@...gle.com>,
        Netdev <netdev@...r.kernel.org>, Daniel Axtens <dja@...ens.net>
Subject: Re: [PATCH RFC] net: Validate size of non-TSO packets in validate_xmit_skb().

On Tue, Feb 26, 2019 at 9:13 AM David Miller <davem@...emloft.net> wrote:
>
> From: Michael Chan <michael.chan@...adcom.com>
> Date: Tue, 26 Feb 2019 05:56:41 -0500
>
> > There have been reports of oversize UDP packets being sent to the
> > driver to be transmitted, causing error conditions.  The issue is
> > likely caused by the dst of the SKB switching between 'lo' with
> > 64K MTU and the hardware device with a smaller MTU.  Patches are
> > being proposed by Mahesh Bandewar <maheshb@...gle.com> to fix the
> > issue.
> >
> > Separately, we should add a length check in validate_xmit_skb()
> > to drop these oversize packets before they reach the driver.
> > This patch only validates non-TSO packets.  Complete validation
> > of segmented TSO packet size will probably be too slow.
> >
> > Signed-off-by: Michael Chan <michael.chan@...adcom.com>
>
> Anything which changes the dst of an SKB really is responsible for
> fixing up whatever became "incompatible" in the new path.
>
> So like Eric I want to see this out of the fast path.

Ok.  In the meantime, will you take a 2-line bnxt_en patch that will
prevent this issue in kernel 5.0?