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 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 EDB24C433B4 for ; Sat, 3 Apr 2021 15:53:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B5964610CF for ; Sat, 3 Apr 2021 15:53:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236873AbhDCPxc (ORCPT ); Sat, 3 Apr 2021 11:53:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34344 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230266AbhDCPxb (ORCPT ); Sat, 3 Apr 2021 11:53:31 -0400 Received: from mail-yb1-xb2c.google.com (mail-yb1-xb2c.google.com [IPv6:2607:f8b0:4864:20::b2c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DD56CC0613E6; Sat, 3 Apr 2021 08:53:26 -0700 (PDT) Received: by mail-yb1-xb2c.google.com with SMTP id l15so8081492ybm.0; Sat, 03 Apr 2021 08:53:26 -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:content-transfer-encoding; bh=0QORQQ85/zORLcruKl4W25E8R6bS7s+xRhix7pPuuzE=; b=Aatz7RP1zMiYQdAsTrrO+XmPiEsJKNmfW6ROxNtEUoyNeB6gy247WSH1OAXpsi5w5z 2On51glSZcnhBLq85rbDmOY4dEcj1+dFb/Y7NrWhv/O1DiqUJxyOZe7tT6MLGTGdTLeU 5xlyNEvQc6/if4Z5PEDzQNTi9O6Iupf33/JeZvRuG3HtDreFtrIjZ01sg7P98K8+1FD7 Zy424Bjt090Z+uYB7fGTlJpcCsXPiIchs3rMjVqh7/vOC/Qr1svR4C7j7Lat8c91Oor8 ooaRRa6vqm7XTFnzBUPvzzH/SchWIWWP+JSo5oo5gmp0sWMBj4wRfBkng85slXq7yHDD Zk3w== 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:content-transfer-encoding; bh=0QORQQ85/zORLcruKl4W25E8R6bS7s+xRhix7pPuuzE=; b=jnmihlYU3EH3OjUAx+tPyX6ScA3KgdTpYg9s8N41yc65jpGE9I0FDtgIvwYPgFpoBe 1/nYAC89clUbqM3oVapdDAeC2HkUSCk5rn2xQ7aN3gbNiAb4tRauqvOvbTdK8o+5+Vgk 2cPoTjzuwgnDpznbE4wiKq1eUXSUUZI/W+17gjErjV+WMMpqhYwh59GYOdKGcqpLL4XP d7KbRJNY/YA4/9oGbuc3gbMviJgV2zV52hfqWw1LhnCmiV/2U1crBsgk3php8g6UOQ2q AJjlXORIANldnvaanSXjbalXkHvIpmHMxWccxy+IFvtol9hhc9OA+OVXh9ACG9Dj1FOT y5sA== X-Gm-Message-State: AOAM533zDe6s6rRwKTyQ55ushjO63S1c6NzET9qYZ7VjGJQMnpxc5ddk 072lTI2IwPmCrodWb2o+NcFDRK+SZEbumPFXcmI= X-Google-Smtp-Source: ABdhPJxyAOSP8SvOxRkrqL6uUAx7A5ZDlierIHAEMBesbHi2wQsnmSDepywX1+BK5rJWgkIMZVGx0k170mVKesvUes4= X-Received: by 2002:a25:9942:: with SMTP id n2mr25148921ybo.230.1617465206168; Sat, 03 Apr 2021 08:53:26 -0700 (PDT) MIME-Version: 1.0 References: <20210330223748.399563-1-pctammela@mojatatu.com> In-Reply-To: From: Andrii Nakryiko Date: Sat, 3 Apr 2021 08:53:15 -0700 Message-ID: Subject: Re: [PATCH bpf-next v2] bpf: check flags in 'bpf_ringbuf_discard()' and 'bpf_ringbuf_submit()' To: Pedro Tammela Cc: Alexei Starovoitov , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Joe Stringer , Quentin Monnet , "open list:BPF (Safe dynamic programs and tools)" , "open list:BPF (Safe dynamic programs and tools)" , open list , Pedro Tammela Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Apr 3, 2021 at 6:29 AM Pedro Tammela wrote: > > Em qua., 31 de mar. de 2021 =C3=A0s 04:02, Andrii Nakryiko > escreveu: > > > > On Tue, Mar 30, 2021 at 4:16 PM Alexei Starovoitov > > wrote: > > > > > > On Tue, Mar 30, 2021 at 3:54 PM Pedro Tammela w= rote: > > > > > > > > BPF_CALL_2(bpf_ringbuf_submit, void *, sample, u64, flags) > > > > { > > > > + if (unlikely(flags & ~(BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKE= UP))) > > > > + return -EINVAL; > > > > + > > > > bpf_ringbuf_commit(sample, flags, false /* discard */); > > > > + > > > > return 0; > > > > > > I think ringbuf design was meant for bpf_ringbuf_submit to never fail= . > > > If we do flag validation it probably should be done at the verifier t= ime. > > > > Oops, replied on another version already. But yes, BPF verifier relies > > on it succeeding. I don't think we can do flags validation at BPF > > verification time, though, because it is defined as non-const integer > > and we do have valid cases where we dynamically determine whether to > > FORCE_WAKEUP or NO_WAKEUP, based on application-driven criteria (e.g., > > amount of enqueued data). > > Then shouldn't we remove the flags check in 'bpf_ringbuf_output()'? bpf_ringbuf_output() combines reserve + commit operations, so if it performs checks before anything is reserved in ringbuf, it's ok for it to fail and return error. So I don't see any problem there. But once it internally reserves, it always proceeds to complete the commit.