From 82b3cc1a2f5e46300a9dec4a8cc8106dc20a4c23 Mon Sep 17 00:00:00 2001
From: Ben McKeegan <ben@netservers.co.uk>
Date: Mon, 16 Nov 2009 03:44:25 +0000
Subject: [PATCH] ppp: fix BUG on non-linear SKB (multilink receive)
PPP does not correctly call pskb_may_pull() on all necessary receive paths
before reading the PPP protocol, thus causing PPP to report seemingly
random 'unsupported protocols' and eventually trigger BUG_ON(skb->len <
skb->data_len) in skb_pull_rcsum() when receiving multilink protocol in
non-linear skbs.
ppp_receive_nonmp_frame() does not call pskb_may_pull() before reading the
protocol number. For the non-mp receive path this is not a problem, as
this check is done in ppp_receive_frame(). For the mp receive path,
ppp_mp_reconstruct() usually copies the data into a new linear skb.
However, in the case where the frame is made up of a single mp fragment,
the mp header is pulled and the existing skb used. This skb was then
passed to ppp_receive_nonmp_frame() without checking if the encapsulated
protocol header could safely be read.
Signed-off-by: Ben McKeegan <ben@netservers.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
drivers/net/ppp_generic.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ppp_generic.c b/drivers/net/ppp_generic.c
index 9bf2a6be9031..965adb6174c3 100644
--- a/drivers/net/ppp_generic.c
+++ b/drivers/net/ppp_generic.c
@@ -1944,8 +1944,15 @@ ppp_receive_mp_frame(struct ppp *ppp, struct sk_buff *skb, struct channel *pch)
}
/* Pull completed packets off the queue and receive them. */
- while ((skb = ppp_mp_reconstruct(ppp)))
- ppp_receive_nonmp_frame(ppp, skb);
+ while ((skb = ppp_mp_reconstruct(ppp))) {
+ if (pskb_may_pull(skb, 2))
+ ppp_receive_nonmp_frame(ppp, skb);
+ else {
+ ++ppp->dev->stats.rx_length_errors;
+ kfree_skb(skb);
+ ppp_receive_error(ppp);
+ }
+ }
return;
--
GitLab