ppp: fix BUG on non-linear SKB (multilink receive)
authorBen McKeegan <ben@netservers.co.uk>
Mon, 16 Nov 2009 03:44:25 +0000 (03:44 +0000)
committerDavid S. Miller <davem@davemloft.net>
Tue, 17 Nov 2009 07:51:34 +0000 (23:51 -0800)
commit82b3cc1a2f5e46300a9dec4a8cc8106dc20a4c23
tree1388b3a52e05a690a1084c06799fb934562901b2
parentc0e1f68bce454d244e2eea6b0ab7b3a217c673d2
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