From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752933AbdF2QXF (ORCPT ); Thu, 29 Jun 2017 12:23:05 -0400 Received: from mail.us.es ([193.147.175.20]:49986 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752841AbdF2QWu (ORCPT ); Thu, 29 Jun 2017 12:22:50 -0400 Date: Thu, 29 Jun 2017 18:22:40 +0200 From: Pablo Neira Ayuso To: Mateusz Jurczyk Cc: Jozsef Kadlecsik , Florian Westphal , "David S. Miller" , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] netfilter: nfnetlink: Improve input length sanitization in nfnetlink_rcv Message-ID: <20170629162240.GA6883@salvia> References: <1496841821.736.35.camel@edumazet-glaptop3.roam.corp.google.com> <20170607135038.1592-1-mjurczyk@google.com> <20170627155825.GA4885@salvia> <20170627170527.GA13513@salvia> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="DocE+STaALJfprDB" Content-Disposition: inline In-Reply-To: <20170627170527.GA13513@salvia> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --DocE+STaALJfprDB Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Tue, Jun 27, 2017 at 07:05:27PM +0200, Pablo Neira Ayuso wrote: > On Tue, Jun 27, 2017 at 05:58:25PM +0200, Pablo Neira Ayuso wrote: > > On Wed, Jun 07, 2017 at 03:50:38PM +0200, Mateusz Jurczyk wrote: > > > Verify that the length of the socket buffer is sufficient to cover the > > > nlmsghdr structure before accessing the nlh->nlmsg_len field for further > > > input sanitization. If the client only supplies 1-3 bytes of data in > > > sk_buff, then nlh->nlmsg_len remains partially uninitialized and > > > contains leftover memory from the corresponding kernel allocation. > > > Operating on such data may result in indeterminate evaluation of the > > > nlmsg_len < NLMSG_HDRLEN expression. > > > > > > The bug was discovered by a runtime instrumentation designed to detect > > > use of uninitialized memory in the kernel. The patch prevents this and > > > other similar tools (e.g. KMSAN) from flagging this behavior in the future. > > > > Applied, thanks. > > Wait, I keeping this back after closer look. > > I think we have to remove this: > > if (nlh->nlmsg_len < NLMSG_HDRLEN || <--- > skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg)) > return; > > in nfnetlink_rcv_skb_batch() > > now that we make this unfront check from nfnetlink_rcv(). BTW, I can just mangle your patch here to delete such line to speed up things. See the mangled patch that is attached to this email. Thanks. --DocE+STaALJfprDB Content-Type: text/x-diff; charset=us-ascii Content-Disposition: attachment; filename="x.patch" diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c index 80f5ecf2c3d7..ff1f4ce6fba4 100644 --- a/net/netfilter/nfnetlink.c +++ b/net/netfilter/nfnetlink.c @@ -463,8 +463,7 @@ static void nfnetlink_rcv_skb_batch(struct sk_buff *skb, struct nlmsghdr *nlh) if (msglen > skb->len) msglen = skb->len; - if (nlh->nlmsg_len < NLMSG_HDRLEN || - skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg)) + if (skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg)) return; err = nla_parse(cda, NFNL_BATCH_MAX, attr, attrlen, nfnl_batch_policy, @@ -491,7 +490,8 @@ static void nfnetlink_rcv(struct sk_buff *skb) { struct nlmsghdr *nlh = nlmsg_hdr(skb); - if (nlh->nlmsg_len < NLMSG_HDRLEN || + if (skb->len < NLMSG_HDRLEN || + nlh->nlmsg_len < NLMSG_HDRLEN || skb->len < nlh->nlmsg_len) return; --DocE+STaALJfprDB--