From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8E332C433F8 for ; Mon, 27 Jul 2020 16:17:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C54A2073E for ; Mon, 27 Jul 2020 16:17:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="T8Sn3a8Q" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731447AbgG0QQw (ORCPT ); Mon, 27 Jul 2020 12:16:52 -0400 Received: from mail.zx2c4.com ([192.95.5.64]:46879 "EHLO mail.zx2c4.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731402AbgG0QQu (ORCPT ); Mon, 27 Jul 2020 12:16:50 -0400 Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTP id 09880da9; Mon, 27 Jul 2020 15:53:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=zx2c4.com; h=mime-version :references:in-reply-to:from:date:message-id:subject:to:cc :content-type; s=mail; bh=yZ9s7iESSXllw2jFppVGJgSQSDc=; b=T8Sn3a 8QgZwT7OBLiEk39YllHL8AHxegeWoSsgukQldc9TiwR4eHH+81jI/awj0HrXtBrg Y5UPc9Cc5BZJ8GrAprgs5NcK5vubz31d4jsM4x0gMeFEgDrVjUrRX41udJBHMNld d/Bx9892A78N/q/07Gl0nQui+mlF/IAoZIyvrYwHlA6vlD8ytQ/RkS4Lp/JjiVOo r0KIpueIg+d9HaYHBQI6Nj9saKViVpoxMt0rA2Xtk8fEZ2Ajc735rEzlQ3Gn8yTu 4eFoXmxypskbeYUzua5Dmfrj+eDOvtFDSR0ScqE+ZC5nUsdiFsBW9DfS1UvXfi+f sWCgYlvemIgM0Wvg== Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 0a17c61b (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Mon, 27 Jul 2020 15:53:25 +0000 (UTC) Received: by mail-il1-f177.google.com with SMTP id b18so8376992ilo.12; Mon, 27 Jul 2020 09:16:45 -0700 (PDT) X-Gm-Message-State: AOAM533rlfDKOj1/MijCyDrrjZl1Y0z0jvOzAJm+qXdBUOMQqOTGi589 KPMgNaN1bCfszWgnF/gQXlrFJS0cH133ROVNtAs= X-Google-Smtp-Source: ABdhPJxpUhiuwtuwnEaez1P/c+ZU0pwKxKQezmeTGc12hGP8McAl6Imm8qRtlhHrSqvTuhro7sF5xCj0r6Sl8qXVeP8= X-Received: by 2002:a92:c804:: with SMTP id v4mr15897355iln.207.1595866604002; Mon, 27 Jul 2020 09:16:44 -0700 (PDT) MIME-Version: 1.0 References: <20200723060908.50081-1-hch@lst.de> <20200723060908.50081-13-hch@lst.de> <20200727150310.GA1632472@zx2c4.com> <20200727150601.GA3447@lst.de> In-Reply-To: <20200727150601.GA3447@lst.de> From: "Jason A. Donenfeld" Date: Mon, 27 Jul 2020 18:16:32 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 12/26] netfilter: switch nf_setsockopt to sockptr_t To: Christoph Hellwig Cc: "David S. Miller" , Jakub Kicinski , Alexei Starovoitov , Daniel Borkmann , Alexey Kuznetsov , Hideaki YOSHIFUJI , Eric Dumazet , Linux Crypto Mailing List , LKML , Netdev , bpf@vger.kernel.org, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, linux-sctp@vger.kernel.org, linux-hams@vger.kernel.org, linux-bluetooth@vger.kernel.org, bridge@lists.linux-foundation.org, linux-can@vger.kernel.org, dccp@vger.kernel.org, linux-decnet-user@lists.sourceforge.net, linux-wpan@vger.kernel.org, linux-s390@vger.kernel.org, mptcp@lists.01.org, lvs-devel@vger.kernel.org, rds-devel@oss.oracle.com, linux-afs@lists.infradead.org, tipc-discussion@lists.sourceforge.net, linux-x25@vger.kernel.org, Kernel Hardening Content-Type: text/plain; charset="UTF-8" Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Mon, Jul 27, 2020 at 5:06 PM Christoph Hellwig wrote: > > On Mon, Jul 27, 2020 at 05:03:10PM +0200, Jason A. Donenfeld wrote: > > Hi Christoph, > > > > On Thu, Jul 23, 2020 at 08:08:54AM +0200, Christoph Hellwig wrote: > > > diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c > > > index da933f99b5d517..42befbf12846c0 100644 > > > --- a/net/ipv4/ip_sockglue.c > > > +++ b/net/ipv4/ip_sockglue.c > > > @@ -1422,7 +1422,8 @@ int ip_setsockopt(struct sock *sk, int level, > > > optname != IP_IPSEC_POLICY && > > > optname != IP_XFRM_POLICY && > > > !ip_mroute_opt(optname)) > > > - err = nf_setsockopt(sk, PF_INET, optname, optval, optlen); > > > + err = nf_setsockopt(sk, PF_INET, optname, USER_SOCKPTR(optval), > > > + optlen); > > > #endif > > > return err; > > > } > > > diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c > > > index 4697d09c98dc3e..f2a9680303d8c0 100644 > > > --- a/net/ipv4/netfilter/ip_tables.c > > > +++ b/net/ipv4/netfilter/ip_tables.c > > > @@ -1102,7 +1102,7 @@ __do_replace(struct net *net, const char *name, unsigned int valid_hooks, > > > } > > > > > > static int > > > -do_replace(struct net *net, const void __user *user, unsigned int len) > > > +do_replace(struct net *net, sockptr_t arg, unsigned int len) > > > { > > > int ret; > > > struct ipt_replace tmp; > > > @@ -1110,7 +1110,7 @@ do_replace(struct net *net, const void __user *user, unsigned int len) > > > void *loc_cpu_entry; > > > struct ipt_entry *iter; > > > > > > - if (copy_from_user(&tmp, user, sizeof(tmp)) != 0) > > > + if (copy_from_sockptr(&tmp, arg, sizeof(tmp)) != 0) > > > return -EFAULT; > > > > > > /* overflow check */ > > > @@ -1126,8 +1126,8 @@ do_replace(struct net *net, const void __user *user, unsigned int len) > > > return -ENOMEM; > > > > > > loc_cpu_entry = newinfo->entries; > > > - if (copy_from_user(loc_cpu_entry, user + sizeof(tmp), > > > - tmp.size) != 0) { > > > + sockptr_advance(arg, sizeof(tmp)); > > > + if (copy_from_sockptr(loc_cpu_entry, arg, tmp.size) != 0) { > > > ret = -EFAULT; > > > goto free_newinfo; > > > } > > > > Something along this path seems to have broken with this patch. An > > invocation of `iptables -A INPUT -m length --length 1360 -j DROP` now > > fails, with > > > > nf_setsockopt->do_replace->translate_table->check_entry_size_and_hooks: > > (unsigned char *)e + e->next_offset > limit ==> TRUE > > > > resulting in the whole call chain returning -EINVAL. It bisects back to > > this commit. This is on net-next. > > This is another use o sockptr_advance that Ido already found a problem > in. I'm looking into this at the moment.. I haven't seen Ido's patch, but it seems clear the issue is that you want to call `sockptr_advance(&arg, sizeof(tmp))`, and adjust sockptr_advance to take a pointer. Slight concern about the whole concept: Things are defined as typedef union { void *kernel; void __user *user; } sockptr_t; static inline bool sockptr_is_kernel(sockptr_t sockptr) { return (unsigned long)sockptr.kernel >= TASK_SIZE; } So what happens if we have some code like: sockptr_t sp; init_user_sockptr(&sp, user_controlled_struct.extra_user_ptr); sockptr_advance(&sp, user_controlled_struct.some_big_offset); copy_to_sockptr(&sp, user_controlled_struct.a_few_bytes, sizeof(user_controlled_struct.a_few_bytes)); With the user controlling some_big_offset, he can convert the user sockptr into a kernel sockptr, causing the subsequent copy_to_sockptr to be a vanilla memcpy, after which a security disaster ensues. Maybe sockptr_advance should have some safety checks and sometimes return -EFAULT? Or you should always use the implementation where being a kernel address is an explicit bit of sockptr_t, rather than being implicit?