netdev - Re: [PATCH net] net: be more gentle about silly gso requests coming from user

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Message-Id: <20200528.163429.484731339357929160.davem@davemloft.net>
Date:   Thu, 28 May 2020 16:34:29 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com, willemb@...gle.com
Subject: Re: [PATCH net] net: be more gentle about silly gso requests
 coming from user

From: Eric Dumazet <edumazet@...gle.com>
Date: Thu, 28 May 2020 14:57:47 -0700

> Recent change in virtio_net_hdr_to_skb() broke some packetdrill tests.
> 
> When --mss=XXX option is set, packetdrill always provide gso_type & gso_size
> for its inbound packets, regardless of packet size.
> 
> 	if (packet->tcp && packet->mss) {
> 		if (packet->ipv4)
> 			gso.gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
> 		else
> 			gso.gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
> 		gso.gso_size = packet->mss;
> 	}
> 
> Since many other programs could do the same, relax virtio_net_hdr_to_skb()
> to no longer return an error, but instead ignore gso settings.
> 
> This keeps Willem intent to make sure no malicious packet could
> reach gso stack.
> 
> Note that TCP stack has a special logic in tcp_set_skb_tso_segs()
> to clear gso_size for small packets.
> 
> Fixes: 6dd912f82680 ("net: check untrusted gso_size at kernel entry")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied and queued up for -stable, thanks Eric.