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=-9.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 CBF67C4727C for ; Wed, 30 Sep 2020 00:00:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E08120897 for ; Wed, 30 Sep 2020 00:00:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="D9uYHkxf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729479AbgI3AAN (ORCPT ); Tue, 29 Sep 2020 20:00:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40678 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728192AbgI3AAM (ORCPT ); Tue, 29 Sep 2020 20:00:12 -0400 Received: from mail-pf1-x444.google.com (mail-pf1-x444.google.com [IPv6:2607:f8b0:4864:20::444]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5DB19C061755; Tue, 29 Sep 2020 17:00:11 -0700 (PDT) Received: by mail-pf1-x444.google.com with SMTP id w7so6463657pfi.4; Tue, 29 Sep 2020 17:00:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=0Pjd53fD2sBc+fXIGlMYU+kpxJEKruFYLrsekrSB8mg=; b=D9uYHkxft0fGH7fMMD/yWKc/gn/G5zYOxivYKUSnQQUpm2oH314eje+pprFgShA5YT QZIBPzREy87bgJWbHo/o6VxNqOc9iCcaN+voJdNUj4XMUAsKT39yYgr0t4Vry5ilqf2+ b/0HtF2djzdsZ222MxN6mGPt5Afx2jtTpn0jlPXFXMTbdvt0rg8dE+/wi/wDrPthBKvD pyYxy8PqONvLuiOWAI4r6f0Xx3i8SB7wV7hTeJP9lfmGrqownSMzctA9pLk7LxZB6JAl lRxI6mcHcq9Zkndaka5966zXTxDBS7+OSOZ71uL6qnzpdoh/lcsTP0wx3ho8AXTE79FK ImSQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=0Pjd53fD2sBc+fXIGlMYU+kpxJEKruFYLrsekrSB8mg=; b=EAtQDAm2HUC0tGEmi/cMQE7cQgDnKITvO5RjJw99yxs5192T3m17mCnf6PZNlMoDfj 4AV2WWgu79+2++Mup8jIQplqgVvlKsl+YCzgaU1m1J03oBNHl3cDJCa3HZgoawC7E8kw eMJgaoesbkj3GBDDVlANR7hQhbsKS1BJZJ6B9LeajSfJFym+OKwPgb5pDE+Zb5aTnZRo +xaGdkGnGw5OSVPlX1MXvl6C56aO3miqNz4y4jFowLFhyS01eWVtRUhGvab22NVhkyXc C1/sVZMkfgQCsb+OmCRvPhw4SBJ0/bb15Egwmxjo1WyOGvhc+pkREjZ7wu/iRg37dTzh J47g== X-Gm-Message-State: AOAM531R3N1dhiyerZDqW5QEbDR66bx9j5yZcg3kW1bIkuzympOw8oun lkutzt49HvbapbTYO04aSMU= X-Google-Smtp-Source: ABdhPJwYCHSXD4ZlwqUov1uBMXaTtndsgo6zJRq/8CJAFWe4fph+aW02zONt8LaxqGzkoJ8wTnm3ug== X-Received: by 2002:a62:5a04:0:b029:142:2501:397f with SMTP id o4-20020a625a040000b02901422501397fmr121880pfb.68.1601424010777; Tue, 29 Sep 2020 17:00:10 -0700 (PDT) Received: from ast-mbp.dhcp.thefacebook.com ([2620:10d:c090:400::5:d27]) by smtp.gmail.com with ESMTPSA id gj6sm28852pjb.10.2020.09.29.17.00.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 29 Sep 2020 17:00:09 -0700 (PDT) Date: Tue, 29 Sep 2020 17:00:07 -0700 From: Alexei Starovoitov To: Song Liu Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com, ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com, kpsingh@chromium.org Subject: Re: [PATCH bpf-next] bpf: fix raw_tp test run in preempt kernel Message-ID: <20200930000007.dgtgbma7rfyeezjx@ast-mbp.dhcp.thefacebook.com> References: <20200929225013.930-1-songliubraving@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200929225013.930-1-songliubraving@fb.com> Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Sep 29, 2020 at 03:50:13PM -0700, Song Liu wrote: > In preempt kernel, BPF_PROG_TEST_RUN on raw_tp triggers: > > [ 35.874974] BUG: using smp_processor_id() in preemptible [00000000] > code: new_name/87 > [ 35.893983] caller is bpf_prog_test_run_raw_tp+0xd4/0x1b0 > [ 35.900124] CPU: 1 PID: 87 Comm: new_name Not tainted 5.9.0-rc6-g615bd02bf #1 > [ 35.907358] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), > BIOS 1.10.2-1ubuntu1 04/01/2014 > [ 35.916941] Call Trace: > [ 35.919660] dump_stack+0x77/0x9b > [ 35.923273] check_preemption_disabled+0xb4/0xc0 > [ 35.928376] bpf_prog_test_run_raw_tp+0xd4/0x1b0 > [ 35.933872] ? selinux_bpf+0xd/0x70 > [ 35.937532] __do_sys_bpf+0x6bb/0x21e0 > [ 35.941570] ? find_held_lock+0x2d/0x90 > [ 35.945687] ? vfs_write+0x150/0x220 > [ 35.949586] do_syscall_64+0x2d/0x40 > [ 35.953443] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Fix this by calling migrate_disable() before smp_processor_id(). > > Fixes: 1b4d60ec162f ("bpf: Enable BPF_PROG_TEST_RUN for raw_tracepoint") > Reported-by: Alexei Starovoitov > Signed-off-by: Song Liu > --- > net/bpf/test_run.c | 20 ++++++++------------ > 1 file changed, 8 insertions(+), 12 deletions(-) > > diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c > index fde5db93507c4..3ea05a5daf544 100644 > --- a/net/bpf/test_run.c > +++ b/net/bpf/test_run.c > @@ -251,11 +251,7 @@ __bpf_prog_test_run_raw_tp(void *data) > { > struct bpf_raw_tp_test_run_info *info = data; > > - rcu_read_lock(); > - migrate_disable(); > info->retval = BPF_PROG_RUN(info->prog, info->ctx); > - migrate_enable(); > - rcu_read_unlock(); I would keep rcu_read_lock here, since there is no need to expand its scope. > } > > int bpf_prog_test_run_raw_tp(struct bpf_prog *prog, > @@ -293,27 +289,27 @@ int bpf_prog_test_run_raw_tp(struct bpf_prog *prog, > > info.prog = prog; > > + rcu_read_lock(); > + migrate_disable(); > if ((kattr->test.flags & BPF_F_TEST_RUN_ON_CPU) == 0 || > cpu == smp_processor_id()) { may be use get_cpu/put_cpu instead? > __bpf_prog_test_run_raw_tp(&info); > - } else { > + } else if (cpu >= nr_cpu_ids || !cpu_online(cpu)) { > /* smp_call_function_single() also checks cpu_online() > * after csd_lock(). However, since cpu is from user > * space, let's do an extra quick check to filter out > * invalid value before smp_call_function_single(). > */ > - if (cpu >= nr_cpu_ids || !cpu_online(cpu)) { > err = -ENXIO; > - goto out; > - } > - > + } else { > err = smp_call_function_single(cpu, __bpf_prog_test_run_raw_tp, > &info, 1); > - if (err) > - goto out; > } > + migrate_enable(); > + rcu_read_unlock(); > > - if (copy_to_user(&uattr->test.retval, &info.retval, sizeof(u32))) > + if (err == 0 && !err would be canonical. > + copy_to_user(&uattr->test.retval, &info.retval, sizeof(u32))) > err = -EFAULT; > > out: > -- > 2.24.1 >