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Subject: Re: KMSAN: uninit-value in pppoe_rcv
To:     Guillaume Nault <g.nault@alphalink.fr>,
        Alexander Potapenko <glider@google.com>
Cc:     Eric Dumazet <eric.dumazet@gmail.com>,
        syzbot+f5f6080811c849739212@syzkaller.appspotmail.com,
        LKML <linux-kernel@vger.kernel.org>, mostrows@earthlink.net,
        Networking <netdev@vger.kernel.org>,
        syzkaller-bugs@googlegroups.com
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 <20180913161929.GA1507@alphalink.fr> <20180913172344.GB1507@alphalink.fr>
From:   Eric Dumazet <eric.dumazet@gmail.com>
Message-ID: <9b41183c-34ea-33d3-a1bf-b0d283675af2@gmail.com>
Date:   Thu, 13 Sep 2018 10:31:16 -0700
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On 09/13/2018 10:23 AM, Guillaume Nault wrote:

> Nothing to change in tun.c. Just some more tests in pppoe.
> Can you try this patch? It only addresses this particular report, not
> the problems spotted by Eric.
> 
> -------- 8< --------
> diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
> index 5aa59f41bf8c..77241b584dff 100644
> --- a/drivers/net/ppp/pppoe.c
> +++ b/drivers/net/ppp/pppoe.c
> @@ -429,6 +429,9 @@ static int pppoe_rcv(struct sk_buff *skb, struct net_device *dev,
>  	if (!skb)
>  		goto out;
>  
> +	if (skb_mac_header_len(skb) < ETH_HLEN)
> +		goto drop;
> +
>  	if (!pskb_may_pull(skb, sizeof(struct pppoe_hdr)))
>  		goto drop;
>  
> 


Yeah this probably will help ;)