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Commit ea8420e9 authored by Simon Arlott's avatar Simon Arlott Committed by David S. Miller
Browse files

ppp_generic: pull 2 bytes so that PPP_PROTO(skb) is valid 



In ppp_input(), PPP_PROTO(skb) may refer to invalid data in the skb.

If this happens and (proto >= 0xc000 || proto == PPP_CCPFRAG) then
the packet is passed directly to pppd.

This occurs frequently when using PPPoE with an interface MTU
greater than 1500 because the skb is more likely to be non-linear.

The next 2 bytes need to be pulled in ppp_input(). The pull of 2
bytes in ppp_receive_frame() has been removed as it is no longer
required.

Signed-off-by: default avatarSimon Arlott <simon@fire.lp0.eu>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1183f383

drivers/net/ppp_generic.c

+18 −11
Original line number Diff line number Diff line
@@ -1567,13 +1567,22 @@ ppp_input(struct ppp_channel *chan, struct sk_buff *skb) 
	struct channel *pch = chan->ppp;

	int proto;



	if (!pch || skb->len == 0) {

	if (!pch) {

		kfree_skb(skb);

		return;

	}



	proto = PPP_PROTO(skb);

	read_lock_bh(&pch->upl);

	if (!pskb_may_pull(skb, 2)) {

		kfree_skb(skb);

		if (pch->ppp) {

			++pch->ppp->dev->stats.rx_length_errors;

			ppp_receive_error(pch->ppp);

		}

		goto done;

	}



	proto = PPP_PROTO(skb);

	if (!pch->ppp || proto >= 0xc000 || proto == PPP_CCPFRAG) {

		/* put it on the channel queue */

		skb_queue_tail(&pch->file.rq, skb);
@@ -1585,6 +1594,8 @@ ppp_input(struct ppp_channel *chan, struct sk_buff *skb) 
	} else {

		ppp_do_recv(pch->ppp, skb, pch);

	}



done:

	read_unlock_bh(&pch->upl);

}
@@ -1617,7 +1628,8 @@ ppp_input_error(struct ppp_channel *chan, int code) 
static void

ppp_receive_frame(struct ppp *ppp, struct sk_buff *skb, struct channel *pch)

{

	if (pskb_may_pull(skb, 2)) {

	/* note: a 0-length skb is used as an error indication */

	if (skb->len > 0) {

#ifdef CONFIG_PPP_MULTILINK

		/* XXX do channel-level decompression here */

		if (PPP_PROTO(skb) == PPP_MP)
@@ -1625,16 +1637,11 @@ ppp_receive_frame(struct ppp *ppp, struct sk_buff *skb, struct channel *pch) 
		else

#endif /* CONFIG_PPP_MULTILINK */

			ppp_receive_nonmp_frame(ppp, skb);

		return;

	}



	if (skb->len > 0)

		/* note: a 0-length skb is used as an error indication */

		++ppp->dev->stats.rx_length_errors;



	} else {

		kfree_skb(skb);

		ppp_receive_error(ppp);

	}

}



static void

ppp_receive_error(struct ppp *ppp)