diff options
authorBen McKeegan <>2009-11-16 03:44:25 +0000
committerDavid S. Miller <>2009-11-16 23:51:34 -0800
commit82b3cc1a2f5e46300a9dec4a8cc8106dc20a4c23 (patch)
parentc0e1f68bce454d244e2eea6b0ab7b3a217c673d2 (diff)
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 <> Signed-off-by: David S. Miller <>
1 files changed, 9 insertions, 2 deletions
diff --git a/drivers/net/ppp_generic.c b/drivers/net/ppp_generic.c
index 9bf2a6be903..965adb6174c 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);
+ }
+ }