netdev - Re: KASAN veth use after free in XDP

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Message-ID: <20230124180230.23ff309e@kicinski-fedora-PC1C0HJN>
Date:   Tue, 24 Jan 2023 18:02:35 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Toke Høiland-Jørgensen <toke@...nel.org>
Cc:     Shawn Bohrer <sbohrer@...udflare.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, makita.toshiaki@....ntt.co.jp
Subject: Re: KASAN veth use after free in XDP_REDIRECT

On Wed, 25 Jan 2023 02:54:52 +0100 Toke Høiland-Jørgensen wrote:
> However, because the skb->head in this case was allocated from a slab
> allocator, taking a page refcount is not enough to prevent it from being
> freed.
> 
> I'm not sure how best to fix this. I guess we could try to detect this
> case in the veth driver and copy the data, like we do for skb_share()
> etc. However, I'm not sure how to actually detect this case...

sbk->head_frag ?