Re: [PATCH net-next] net: fix up truesize of cloned skb in skb_prepare_for_shift()

[Eric Dumazet]

On Mon, Feb 1, 2021 at 6:34 PM Marco Elver <elver@xxxxxxxxxx> wrote:
>
> On Mon, 1 Feb 2021 at 17:50, Christoph Paasch

> > just a few days ago we found out that this also fixes a syzkaller
> > issue on MPTCP (https://github.com/multipath-tcp/mptcp_net-next/issues/136).
> > I confirmed that this patch fixes the issue for us as well:
> >
> > Tested-by: Christoph Paasch <christoph.paasch@xxxxxxxxx>
>
> That's interesting, because according to your config you did not have
> KFENCE enabled. Although it's hard to say what exactly caused the
> truesize mismatch in your case, because it clearly can't be KFENCE
> that caused ksize(kmalloc(S))!=ksize(kmalloc(S)) for you.

Indeed, this seems strange. This might be a different issue.

Maybe S != S ;)