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=-5.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 77153C433DB for ; Wed, 17 Feb 2021 23:19:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 34C3864DDA for ; Wed, 17 Feb 2021 23:19:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231613AbhBQXTG (ORCPT ); Wed, 17 Feb 2021 18:19:06 -0500 Received: from mail.zx2c4.com ([104.131.123.232]:50168 "EHLO mail.zx2c4.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229774AbhBQXTD (ORCPT ); Wed, 17 Feb 2021 18:19:03 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1613603900; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=AdrWV+0RqhKCTxk9ZB3XViePvtjikVcHH9GgVrWTd7k=; b=O+2A58Bl3UDsyNIyinZjpQM9ivnsh1sOLIQka876ehzrRILUCXsUkUTQk5rjCHhlN7BNz+ WGPLnZydELSSq4c7LuY18LrsewQOLFjvF3DrQ88sIyDGST6llAvXKwL8qKB/KwZ33YC8lP crbbwE0IffNQBN9o9w37DduavYA24GM= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id a67271fe (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Wed, 17 Feb 2021 23:18:20 +0000 (UTC) Received: by mail-yb1-f175.google.com with SMTP id u3so341023ybk.6; Wed, 17 Feb 2021 15:18:20 -0800 (PST) X-Gm-Message-State: AOAM530WHkyxJjmO9ulUdkgMBz6eKj9RACrD7D7ZX07iQsZwlS1PtHYz TXmPqtIEoMGp7anU06SrN+d5y5jYXJlMh6xpqjw= X-Google-Smtp-Source: ABdhPJzHFoKDH/ZMtpGk4JJaz0HtVODj3UjZQBaRjwppT6zywQcfNjkMCTDE2i6TWrTwHS8e5Ss25NMgNFsfNnp1p8A= X-Received: by 2002:a25:4981:: with SMTP id w123mr2560681yba.123.1613603900090; Wed, 17 Feb 2021 15:18:20 -0800 (PST) MIME-Version: 1.0 Received: by 2002:a05:7110:8013:b029:34:f999:a3fe with HTTP; Wed, 17 Feb 2021 15:18:19 -0800 (PST) In-Reply-To: References: From: "Jason A. Donenfeld" Date: Thu, 18 Feb 2021 00:18:19 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: possible stack corruption in icmp_send (__stack_chk_fail) To: Willem de Bruijn Cc: Netdev , LKML , Willem de Bruijn Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2/18/21, Willem de Bruijn wrote: > On Wed, Feb 17, 2021 at 5:56 PM Jason A. Donenfeld wrote: >> >> Hi Willem, >> >> On Wed, Feb 17, 2021 at 11:27 PM Willem de Bruijn >> wrote: >> > A vmlinux image might help. I couldn't find one for this kernel. >> >> https://data.zx2c4.com/icmp_send-crash-e03b4a42-706a-43bf-bc40-1f15966b3216.tar.xz >> has .debs with vmlinuz in there, which you can extract to vmlinux, as >> well as my own vmlinux elf construction with the symbols added back in >> by extracting them from kallsyms. That's the best I've been able to >> do, as all of this is coming from somebody random emailing me. >> >> > But could it be >> > that the forwarded packet is not sensible IPv4? The skb->protocol is >> > inferred in wg_packet_consume_data_done->ip_tunnel_parse_protocol. >> >> The wg calls to icmp_ndo_send are gated by checking skb->protocol: >> >> if (skb->protocol == htons(ETH_P_IP)) >> icmp_ndo_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, >> 0); >> else if (skb->protocol == htons(ETH_P_IPV6)) >> icmpv6_ndo_send(skb, ICMPV6_DEST_UNREACH, >> ICMPV6_ADDR_UNREACH, 0); >> >> On the other hand, that code is hit on an error path when >> wg_check_packet_protocol returns false: >> >> static inline bool wg_check_packet_protocol(struct sk_buff *skb) >> { >> __be16 real_protocol = ip_tunnel_parse_protocol(skb); >> return real_protocol && skb->protocol == real_protocol; >> } >> >> So that means, at least in theory, icmp_ndo_send could be called with >> skb->protocol != ip_tunnel_parse_protocol(skb). I guess I can address >> that. But... is it actually a problem? > > For this forwarded packet that arrived on a wireguard tunnel, > skb->protocol was originally also set by ip_tunnel_parse_protocol. > So likely not. > > The other issue seems more like a real bug. wg_xmit calling > icmp_ndo_send without clearing IPCB first. > Bingo! Nice eye! I confirmed the crash by just memsetting 0x41 to cb before the call. Clearly this should be zeroed by icmp_ndo_xmit. Will send a patch for icmp_ndo_xmit momentarily and will CC you. Jason