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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 7D076C43603 for ; Fri, 20 Dec 2019 01:11:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5E1F22467E for ; Fri, 20 Dec 2019 01:11:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727209AbfLTBLa (ORCPT ); Thu, 19 Dec 2019 20:11:30 -0500 Received: from correo.us.es ([193.147.175.20]:48106 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727006AbfLTBLa (ORCPT ); Thu, 19 Dec 2019 20:11:30 -0500 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id C7689F25A9 for ; Fri, 20 Dec 2019 02:11:26 +0100 (CET) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id B8A3CDA70F for ; Fri, 20 Dec 2019 02:11:26 +0100 (CET) Received: by antivirus1-rhel7.int (Postfix, from userid 99) id ADE42DA709; Fri, 20 Dec 2019 02:11:26 +0100 (CET) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 93F60DA70A; Fri, 20 Dec 2019 02:11:24 +0100 (CET) Received: from 192.168.1.97 (192.168.1.97) by antivirus1-rhel7.int (F-Secure/fsigk_smtp/550/antivirus1-rhel7.int); Fri, 20 Dec 2019 02:11:24 +0100 (CET) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/antivirus1-rhel7.int) Received: from us.es (sys.soleta.eu [212.170.55.40]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: 1984lsi) by entrada.int (Postfix) with ESMTPSA id 76C9A4265A5A; Fri, 20 Dec 2019 02:11:24 +0100 (CET) Date: Fri, 20 Dec 2019 02:11:24 +0100 X-SMTPAUTHUS: auth mail.us.es From: Pablo Neira Ayuso To: Florian Westphal Cc: netfilter-devel@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, syzbot+f68108fed972453a0ad4@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com Subject: Re: [PATCH nf] netfilter: ebtables: compat: reject all padding in matches/watchers Message-ID: <20191220011124.addyezhijttukqw5@salvia> References: <000000000000cd9e600599b051e5@google.com> <20191215024925.10872-1-fw@strlen.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191215024925.10872-1-fw@strlen.de> User-Agent: NeoMutt/20170113 (1.7.2) X-Virus-Scanned: ClamAV using ClamSMTP Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sun, Dec 15, 2019 at 03:49:25AM +0100, Florian Westphal wrote: > syzbot reported following splat: > > BUG: KASAN: vmalloc-out-of-bounds in size_entry_mwt net/bridge/netfilter/ebtables.c:2063 [inline] > BUG: KASAN: vmalloc-out-of-bounds in compat_copy_entries+0x128b/0x1380 net/bridge/netfilter/ebtables.c:2155 > Read of size 4 at addr ffffc900004461f4 by task syz-executor267/7937 > > CPU: 1 PID: 7937 Comm: syz-executor267 Not tainted 5.5.0-rc1-syzkaller #0 > size_entry_mwt net/bridge/netfilter/ebtables.c:2063 [inline] > compat_copy_entries+0x128b/0x1380 net/bridge/netfilter/ebtables.c:2155 > compat_do_replace+0x344/0x720 net/bridge/netfilter/ebtables.c:2249 > compat_do_ebt_set_ctl+0x22f/0x27e net/bridge/netfilter/ebtables.c:2333 > [..] > > Because padding isn't considered during computation of ->buf_user_offset, > "total" is decremented by fewer bytes than it should. > > Therefore, the first part of > > if (*total < sizeof(*entry) || entry->next_offset < sizeof(*entry)) > > will pass, -- it should not have. This causes oob access: > entry->next_offset is past the vmalloced size. > > Reject padding and check that computed user offset (sum of ebt_entry > structure plus all individual matches/watchers/targets) is same > value that userspace gave us as the offset of the next entry. Applied, thanks.