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

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Message-Id: <20190226.091324.1656342529138987636.davem@davemloft.net>
Date:   Tue, 26 Feb 2019 09:13:24 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     michael.chan@...adcom.com
Cc:     maheshb@...gle.com, edumazet@...gle.com, dja@...ens.net,
        netdev@...r.kernel.org
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 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.