netdev - [PATCH] llc: dont trust payload size on test cmd

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Message-ID: <20080225161439.GZ84358@surrealistic.net>
Date:	Mon, 25 Feb 2008 08:14:39 -0800
From:	Jim Westfall <jwestfall@...realistic.net>
To:	netdev@...r.kernel.org, acme@...stprotocols.net
Subject: [PATCH] llc: dont trust payload size on test cmd

Hi

In testing its not safe to trust the payload length we are given in a
received llc test command header.  Instead we should calculate this 
ourselves or run the risk of an skb_over_panic() if the received length in 
the header is > then the actual payload size.

Signed-off-by: Jim Westfall <jwestfall@...realistic.net>

diff -urp linux-2.6.24.2.org/include/net/llc_pdu.h linux-2.6.24.2/include/net/llc_pdu.h
--- linux-2.6.24.2.org/include/net/llc_pdu.h	2008-02-10 21:51:11.000000000 -0800
+++ linux-2.6.24.2/include/net/llc_pdu.h	2008-02-24 10:23:02.000000000 -0800
@@ -348,7 +348,7 @@ static inline void llc_pdu_init_as_test_
 		struct llc_pdu_un *ev_pdu = llc_pdu_un_hdr(ev_skb);
 		int dsize;
 
-		dsize = ntohs(eth_hdr(ev_skb)->h_proto) - 3;
+		dsize = (ev_skb->tail - (u8 *)ev_pdu) - 3;
 		memcpy(((u8 *)pdu) + 3, ((u8 *)ev_pdu) + 3, dsize);
 		skb_put(skb, dsize);
 	}

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