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=-2.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 1C6C4C4320A for ; Wed, 28 Jul 2021 03:17:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F35F86018A for ; Wed, 28 Jul 2021 03:17:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234530AbhG1DR6 (ORCPT ); Tue, 27 Jul 2021 23:17:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54574 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233437AbhG1DR5 (ORCPT ); Tue, 27 Jul 2021 23:17:57 -0400 Received: from mail-pj1-x102b.google.com (mail-pj1-x102b.google.com [IPv6:2607:f8b0:4864:20::102b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 20E9EC061757; Tue, 27 Jul 2021 20:17:57 -0700 (PDT) Received: by mail-pj1-x102b.google.com with SMTP id e2-20020a17090a4a02b029016f3020d867so2210560pjh.3; Tue, 27 Jul 2021 20:17:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Dsf2sGa5jV2kjDjS35k1g7HufVmqs15n/JN/JKFWpGc=; b=OBzTcRUKWDdskdvj6UWxZXcPANCb4hsjnev6nV+DaMluvUGdtHuyH0m+ix1Wq3SvVs GStjN8cTWb+wYZ6hexIrprXWt1K1I8XO+P33JhbkHxQ3nAknaE1A8kc/lCe0pyrobX7B fl6g3rYHXkVgw5iGNxUFtFbjGxKeQMKIp2QU6j3Dh6GazJBTUGOXC+LF5bzj0Ps4vNHT bSXn9Quh52Oz2/ld4lj8BDKXiiIbgKMEe7BmpVUVrbo+UPdM1DAvi8QvdX7DlqDYPI+r XL9t2Y44OlsKT7JyIr/Xo69Jz31UJpYFzAa45v2Zu3eLMEQqtiVcLF57yZwKcRq4CkI1 FEuQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Dsf2sGa5jV2kjDjS35k1g7HufVmqs15n/JN/JKFWpGc=; b=ZG8+SVzJSdn+G+PijzVB5l8hMgmj0G8JFkc0Tlw27fCyTvG7xoWC8GF03Pnr8oLdUh YHs8rxFIkHbCxJyYrB1iKbOZWMvq4R08yLYayuF6z+RNB716aUWVoL1LSUh1m/o2SfHY hKT8zChWQnSEefTpyTWO0RCtaqPXNThJqV3O5PNfjOAFFndYtyEVazJokEoCxBBu5lF1 Q48UkDX2qLJ6ZoyYah17JOVBD2JnxCrzw7gF8UMlsjPz/IXR0HUwz9UuJbKw1acvx80b 4GG77EELEjiJAVSkUPjH9FNrt3pRUeRMUi1bNpHi16wMkn7vq25FHFawj+IlwGiDEPHj poyA== X-Gm-Message-State: AOAM533hiuYwvpIRvpUa4wXYVmyI6ed3pm1miMvGxqtPOtXh6azVpE3w icLqze4diA9yqM1dCyZfmY7K0rhGHINa6x13xrA= X-Google-Smtp-Source: ABdhPJyLAHiJQhIHgjAibpUxV/lgyqUQp0vfdLmMXbYjqlfERTXlN9UpptmSiLL8O5RCbACmq5O1GBxqCKYgUQhnQA8= X-Received: by 2002:a63:dd4a:: with SMTP id g10mr26923790pgj.179.1627442276573; Tue, 27 Jul 2021 20:17:56 -0700 (PDT) MIME-Version: 1.0 References: <20210715055923.43126-1-xiyou.wangcong@gmail.com> <202107230000.B52B102@keescook> In-Reply-To: <202107230000.B52B102@keescook> From: Cong Wang Date: Tue, 27 Jul 2021 20:17:45 -0700 Message-ID: Subject: Re: [Patch net-next resend v2] net: use %px to print skb address in trace_netif_receive_skb To: Kees Cook Cc: Qitao Xu , "David S. Miller" , Linux Kernel Network Developers , Cong Wang , Linus Torvalds , linux-hardening@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Jul 23, 2021 at 12:09 AM Kees Cook wrote: > > On Wed, Jul 14, 2021 at 10:59:23PM -0700, Cong Wang wrote: > > From: Qitao Xu > > > > The print format of skb adress in tracepoint class net_dev_template > > is changed to %px from %p, because we want to use skb address > > as a quick way to identify a packet. > > No; %p was already hashed to uniquely identify unique addresses. This > is needlessly exposing kernel addresses with no change in utility. See > [1] for full details on when %px is justified (almost never). This is clearly not true. Trust us, we _did_ use %p in the beginning, it does not work at all. See the trace below captured with %p: -0 [012] ..s. 385.248024: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=56 -0 [012] ..s. 385.261602: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=38 -0 [012] ..s. 387.245617: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=38 -0 [012] ..s. 389.293621: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=38 -0 [012] ..s. 391.277637: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=38 -0 [012] ..s. 392.939159: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=60 -0 [012] .Ns. 392.939197: ip_rcv: skbaddr=000000003fa575fb -0 [012] .Ns. 392.939286: ip_local_deliver_finish: skbaddr=000000003fa575fb kworker/12:1-122 [012] ..s. 392.939369: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=52 kworker/12:1-122 [012] ..s. 392.939371: ip_rcv: skbaddr=000000003fa575fb kworker/12:1-122 [012] ..s. 392.939409: ip_local_deliver_finish: skbaddr=000000003fa575fb -0 [012] ..s. 393.261605: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=38 -0 [012] ..s. 395.174268: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=56 -0 [012] ..s. 395.174275: ip_rcv: skbaddr=000000003fa575fb -0 [012] ..s. 395.174284: sk_data_ready: skaddr=0000000049f7d0d9, skbaddr=000000003fa575fb -0 [012] .Ns. 395.174337: tcp_v4_rcv: sport=8801 dport=15884 saddr=192.168.122.139 daddr=192.168.122.1 saddrv6=::ffff:192.168.122.139 daddrv6=::ffff:192.168.122.1 state=TCP_ESTABLISHED skbaddr=000000003fa575fb -0 [012] .Ns. 395.174338: ip_local_deliver_finish: skbaddr=000000003fa575fb -0 [012] ..s. 395.245605: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=38 -0 [012] ..s. 397.293632: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=38 -0 [012] ..s. 397.352766: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=56 -0 [012] ..s. 397.352771: ip_rcv: skbaddr=000000003fa575fb -0 [012] ..s. 397.352813: sk_data_ready: skaddr=0000000049f7d0d9, skbaddr=000000003fa575fb -0 [012] .Ns. 397.352819: tcp_v4_rcv: sport=8801 dport=15884 saddr=192.168.122.139 daddr=192.168.122.1 saddrv6=::ffff:192.168.122.139 daddrv6=::ffff:192.168.122.1 state=TCP_ESTABLISHED skbaddr=000000003fa575fb -0 [012] .Ns. 397.352819: ip_local_deliver_finish: skbaddr=000000003fa575fb -0 [012] ..s. 399.277623: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=38 -0 [012] ..s. 401.261640: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=38 -0 [012] ..s. 402.671285: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=56 -0 [012] ..s. 402.671294: ip_rcv: skbaddr=000000003fa575fb -0 [012] ..s. 402.671344: sk_data_ready: skaddr=0000000049f7d0d9, skbaddr=000000003fa575fb -0 [012] .Ns. 402.671355: tcp_v4_rcv: sport=8801 dport=15884 saddr=192.168.122.139 daddr=192.168.122.1 saddrv6=::ffff:192.168.122.139 daddrv6=::ffff:192.168.122.1 state=TCP_ESTABLISHED skbaddr=000000003fa575fb -0 [012] .Ns. 402.671356: ip_local_deliver_finish: skbaddr=000000003fa575fb -0 [012] ..s. 403.245617: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=38 -0 [012] ..s. 403.688075: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=52 -0 [012] ..s. 403.688080: ip_rcv: skbaddr=000000003fa575fb -0 [012] .Ns. 403.688092: sk_data_ready: skaddr=0000000049f7d0d9, skbaddr=000000003fa575fb -0 [012] .Ns. 403.688094: tcp_v4_rcv: sport=8801 dport=15884 saddr=192.168.122.139 daddr=192.168.122.1 saddrv6=::ffff:192.168.122.139 daddrv6=::ffff:192.168.122.1 state=TCP_CLOSE_WAIT skbaddr=000000003fa575fb -0 [012] .Ns. 403.688095: ip_local_deliver_finish: skbaddr=000000003fa575fb nc-1044 [012] ..s. 403.688222: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=52 nc-1044 [012] ..s. 403.688222: ip_rcv: skbaddr=000000003fa575fb nc-1044 [012] ..s. 403.688237: tcp_v4_rcv: sport=8801 dport=15884 saddr=192.168.122.139 daddr=192.168.122.1 saddrv6=::ffff:192.168.122.139 daddrv6=::ffff:192.168.122.1 state=TCP_CLOSE skbaddr=000000003fa575fb nc-1044 [012] ..s. 403.688246: ip_local_deliver_finish: skbaddr=000000003fa575fb -0 [012] ..s. 405.293625: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=38 -0 [012] ..s. 407.137723: netif_receive_skb: dev=eth0 skbaddr=000000003fa575fb len=222 > > > Note, trace ring buffer is only accessible to privileged users, > > it is safe to use a real kernel address here. > > That's not accurate either; there is a difference between uid 0 and > kernel mode privilege levels. Not sure how accurate we can be just to make you happy. Please give us a pointer on the accuracy. Thanks.