Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751778AbdF3PTJ (ORCPT ); Fri, 30 Jun 2017 11:19:09 -0400 Received: from mail-yw0-f180.google.com ([209.85.161.180]:32984 "EHLO mail-yw0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751560AbdF3PTH (ORCPT ); Fri, 30 Jun 2017 11:19:07 -0400 MIME-Version: 1.0 In-Reply-To: <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> <20170629162240.GA6883@salvia> From: Mateusz Jurczyk Date: Fri, 30 Jun 2017 17:19:05 +0200 Message-ID: Subject: Re: [PATCH v2] netfilter: nfnetlink: Improve input length sanitization in nfnetlink_rcv To: Pablo Neira Ayuso 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 Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1676 Lines: 35 On Thu, Jun 29, 2017 at 6:22 PM, Pablo Neira Ayuso wrote: > 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. Sure, I think the condition in nfnetlink_rcv_skb_batch() can be now safely removed. Feel free to proceed with the mangled patch. Thanks.