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

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Date:   Tue, 26 Feb 2019 13:16:58 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     michael.chan@...adcom.com
Cc:     maheshb@...gle.com, edumazet@...gle.com, netdev@...r.kernel.org,
        dja@...ens.net
Subject: Re: [PATCH RFC] net: Validate size of non-TSO packets in
 validate_xmit_skb().

From: Michael Chan <michael.chan@...adcom.com>
Date: Tue, 26 Feb 2019 10:22:42 -0800

> 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?

Sure, but we will have to remember to remove it when it is no longer
necessary...