From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH] ppp: fix BUG on non-linear SKB (multilink receive) Date: Mon, 16 Nov 2009 23:52:54 -0800 (PST) Message-ID: <20091116.235254.148428748.davem@davemloft.net> References: <20091113.194650.214404898.davem@davemloft.net> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: paulus@samba.org, netdev@vger.kernel.org, linux-ppp@vger.kernel.org To: ben@netservers.co.uk Return-path: In-Reply-To: Sender: linux-ppp-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: Ben McKeegan Date: Mon, 16 Nov 2009 13:44:25 +0000 (GMT) > 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 Applied but: > + while ((skb = ppp_mp_reconstruct(ppp))) { > + if (pskb_may_pull(skb, 2)) There is a mix of space and tab characters leading up to the "if (pskb_may_pull" there, I fixed it up but please take care of such trivial issues before submitting your patch next time. Thanks.