On Tue, 2017-08-22 at 11:01 -0700, David Miller wrote:
> From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
> Date: Tue, 22 Aug 2017 20:55:56 +0300
>
> > Which reminds me that skb_linearize in net core seems to be
> > fundamentally racy - I suspect that if skb is cloned, and someone is
> > trying to use the shared frags while another thread calls skb_linearize,
> > we get some use after free bugs which likely mostly go undetected
> > because the corrupted packets mostly go on wire and get dropped
> > by checksum code.
>
> Indeed, it does assume that the skb from which the clone was made
> never has it's geometry changed.
>
> I don't think even the TCP retransmit queue has this guarantee.
TCP retransmit makes sure to avoid that.
if (skb_unclone(skb, GFP_ATOMIC))
return -ENOMEM;
( Before cloning again skb )
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