netdev - TCP_COOKIE_TRANSACTIONS synack data

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Message-ID: <2BC93087D531FF4A98881820AFE8AE7B74C409E1C3@jklmail01.ixonos.local>
Date:	Mon, 8 Mar 2010 16:27:25 +0200
From:	Penttilä Mika <mika.penttila@...nos.com>
To:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: TCP_COOKIE_TRANSACTIONS synack data


The TCP_COOKIE_TRANSACTIONS synack data seems pretty unsafe atm. 
>From tcp_make_synack():


	u8 *buf = skb_put(skb, cvp->s_data_desired);

	/* copy data directly from the listening socket. */
    	memcpy(buf, cvp->s_data_payload, cvp->s_data_desired);


The skb here is allocated for MAX_TCP_HEADER + 15 and synack data could be as long as TCP_MSS_DEFAULT, panic():ing at the skb_put().

--Mika


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