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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8AEEAC43334 for ; Thu, 2 Jun 2022 16:02:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236721AbiFBQCd (ORCPT ); Thu, 2 Jun 2022 12:02:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230011AbiFBQCc (ORCPT ); Thu, 2 Jun 2022 12:02:32 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F05571DB1C6; Thu, 2 Jun 2022 09:02:30 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 775F0614BA; Thu, 2 Jun 2022 16:02:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2AFACC385A5; Thu, 2 Jun 2022 16:02:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1654185749; bh=PQ/ALFmc2rHdOMOvBYplDDZYqrr95PM1qDGM+8q0FAY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=mAsxZWaNR/QCVzI/KMLuaYYMq4HjEk6FQW7TVSJz/CmyQczSXlcNOoMHmO2EpmcOe UzN+KPjNABEB9ArOPggjKcyF1kE6TGlosSCEYrJaiFPh5R3BOe1K1vCakgbtyqR5YI TjvpMudqRkrgVPHe1ka9HbAqRNT7we7zqQoQnUN/79Zhuezezg6EXGPmoQ2t/zBcew Y73oAnL0mSb+6ylxyysFYQAKIsO7QCEmmzWiJmK5czWxKvy8YVO4M7zv1tD5C3qkb4 KEbo5+Cva8b62qeHZ8jnTOCoJbhG0F4KY6OFbv83+dtd3VwucxLvZPFWultDTAcmlT a3fdTQGzl0sUg== Date: Thu, 2 Jun 2022 09:02:28 -0700 From: Jakub Kicinski To: Paolo Abeni Cc: Wang Yufen , davem@davemloft.net, yoshfuji@linux-ipv6.org, dsahern@kernel.org, edumazet@google.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH net-next v4] ipv6: Fix signed integer overflow in __ip6_append_data Message-ID: <20220602090228.1e493e47@kernel.org> In-Reply-To: <4c9e3cf5122f4c2f8a2473c493891362e0a13b4a.camel@redhat.com> References: <20220601084803.1833344-1-wangyufen@huawei.com> <4c9e3cf5122f4c2f8a2473c493891362e0a13b4a.camel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, 02 Jun 2022 12:38:10 +0200 Paolo Abeni wrote: > I'm sorry for the multiple incremental feedback on this patch. It's > somewhat tricky. > > AFAICS Jakub mentioned only udpv6_sendmsg(). In l2tp_ip6_sendmsg() we > can have an overflow: > > int transhdrlen = 4; /* zero session-id */ > int ulen = len + transhdrlen; > > when len >= INT_MAX - 4. That will be harmless, but I guess it could > still trigger a noisy UBSAN splat. Good point, I wonder if that's a separate issue. Should we follow what UDP does and subtract the transhdr from the max? My gut feeling is that stricter checks are cleaner than just bumping variable sizes. diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c index c6ff8bf9b55f..9dbd801ddb98 100644 --- a/net/l2tp/l2tp_ip6.c +++ b/net/l2tp/l2tp_ip6.c @@ -504,14 +504,15 @@ static int l2tp_ip6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) struct ipcm6_cookie ipc6; int addr_len = msg->msg_namelen; int transhdrlen = 4; /* zero session-id */ - int ulen = len + transhdrlen; + int ulen; int err; /* Rough check on arithmetic overflow, * better check is made in ip6_append_data(). */ - if (len > INT_MAX) + if (len > INT_MAX - transhdrlen) return -EMSGSIZE; + ulen = len + transhdrlen; /* Mirror BSD error message compatibility */ if (msg->msg_flags & MSG_OOB)