netdev - Re: [PATCH net] net: stricter validation of untrusted gso packets

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Message-Id: <20200506.172338.1702704236989217382.davem@davemloft.net>
Date:   Wed, 06 May 2020 17:23:38 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     willemdebruijn.kernel@...il.com
Cc:     netdev@...r.kernel.org, willemb@...gle.com,
        syzkaller@...glegroups.com
Subject: Re: [PATCH net] net: stricter validation of untrusted gso packets

From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Date: Mon,  4 May 2020 12:48:54 -0400

> From: Willem de Bruijn <willemb@...gle.com>
> 
> Syzkaller again found a path to a kernel crash through bad gso input:
> a packet with transport header extending beyond skb_headlen(skb).
> 
> Tighten validation at kernel entry:
> 
> - Verify that the transport header lies within the linear section.
> 
>     To avoid pulling linux/tcp.h, verify just sizeof tcphdr.
>     tcp_gso_segment will call pskb_may_pull (th->doff * 4) before use.
> 
> - Match the gso_type against the ip_proto found by the flow dissector.
> 
> Fixes: bfd5f4a3d605 ("packet: Add GSO/csum offload support.")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>

Applied and queued up for -stable, thanks.