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: Simon Arlott <simon@fire.lp0.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ppp_generic.c b/drivers/net/ppp_generic.c
index 6e281bc..75e8903 100644
--- a/drivers/net/ppp_generic.c
+++ b/drivers/net/ppp_generic.c
@@ -1567,13 +1567,22 @@
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 @@
} else {
ppp_do_recv(pch->ppp, skb, pch);
}
+
+done:
read_unlock_bh(&pch->upl);
}
@@ -1617,7 +1628,8 @@
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)
@@ -1625,15 +1637,10 @@
else
#endif /* CONFIG_PPP_MULTILINK */
ppp_receive_nonmp_frame(ppp, skb);
- return;
+ } else {
+ kfree_skb(skb);
+ ppp_receive_error(ppp);
}
-
- if (skb->len > 0)
- /* note: a 0-length skb is used as an error indication */
- ++ppp->dev->stats.rx_length_errors;
-
- kfree_skb(skb);
- ppp_receive_error(ppp);
}
static void
