netdev - Re: BUG in skb_pull with e1000e, PPTP, and L2TP

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Date:	Tue, 18 Oct 2011 05:51:19 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Bradley Peterson <despite@...il.com>
Cc:	netdev@...r.kernel.org, Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Bruce Allan <bruce.w.allan@...el.com>,
	Carolyn Wyborny <carolyn.wyborny@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>,
	Greg Rose <gregory.v.rose@...el.com>,
	PJ Waskiewicz <peter.p.waskiewicz.jr@...el.com>,
	Alex Duyck <alexander.h.duyck@...el.com>,
	John Ronciak <john.ronciak@...el.com>,
	e1000-devel@...ts.sourceforge.net
Subject: Re: BUG in skb_pull with e1000e, PPTP, and L2TP

Le mardi 18 octobre 2011 à 04:24 +0200, Eric Dumazet a écrit :

> diff --git a/drivers/net/ppp/pptp.c b/drivers/net/ppp/pptp.c
> index eae542a..d0197e3 100644
> --- a/drivers/net/ppp/pptp.c
> +++ b/drivers/net/ppp/pptp.c
> @@ -305,11 +305,16 @@ static int pptp_rcv_core(struct sock *sk, struct sk_buff *skb)
>  	}
>  
>  	header = (struct pptp_gre_header *)(skb->data);
> +	headersize  = sizeof(*header);
>  
>  	/* test if acknowledgement present */
>  	if (PPTP_GRE_IS_A(header->ver)) {
> -		__u32 ack = (PPTP_GRE_IS_S(header->flags)) ?
> -				header->ack : header->seq; /* ack in different place if S = 0 */
> +		__u32 ack;
> +
> +		if (!pskb_may_pull(skb, headersize))
> +			goto drop;

Oh well, this is buggy, I need to set header again, I'll send an updated
patch

		header = (struct pptp_gre_header *)(skb->data);

> +		ack = (PPTP_GRE_IS_S(header->flags)) ?
> +			header->ack : header->seq; /* ack in different place if S = 0 */
>  



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