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=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 B174BC433B4 for ; Wed, 5 May 2021 18:45:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 811486105A for ; Wed, 5 May 2021 18:45:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234797AbhEESq1 (ORCPT ); Wed, 5 May 2021 14:46:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39244 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234553AbhEESq0 (ORCPT ); Wed, 5 May 2021 14:46:26 -0400 Received: from mail-yb1-xb34.google.com (mail-yb1-xb34.google.com [IPv6:2607:f8b0:4864:20::b34]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3E7AC061574; Wed, 5 May 2021 11:45:29 -0700 (PDT) Received: by mail-yb1-xb34.google.com with SMTP id e190so3983510ybb.10; Wed, 05 May 2021 11:45:29 -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=CsndVLEjExynmF5y+I8VPPu8kM+YFPUfsGJirIMwSTA=; b=c7AcGP4J85XixSfyOnSK/KUebnruNUT59GYprfYw+UprsKh9XIW1sVriE2j9yHbGQS wDHZmPz7U3mz++AHtrLC441n2xE3aH48wLtXLNkecYH5ToeSVtbwnbw6bHZ62Fv0yzjL sYz//bLezUXbogEMKFZR2bkK6CDQjVJJ0+BPWmhzyQEktJEvmalPzWsx/BQmtnhNHQup 5bO95TBj+jaNoSkyL/47QiyDz5cQHxYRa1N2quD+iYfsXWoQhk/jVD4a6PiU42HSoXJa e4f7fm4+lbeN4UkTI3KHzCGxKktc8SBy0dlplsCQPX7NlKzbDsmNYACFt3pqPWjPWvgM adkw== 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=CsndVLEjExynmF5y+I8VPPu8kM+YFPUfsGJirIMwSTA=; b=TCEob7F+p92EUkccM4rIQrckCLltaVPlQz9SYHPR/eL3AhEOqoKw1itwFNvPzsgntq nWrRq6jENe4pC+c5HA53324oVL9tvC5y544hMrvw+L/r22BMwSJGEyn6Tek5PdojvYS4 jSm3+x7tgQOeILmH6zrFVQjrsyH3EKFaWyDQEfZZH6rsTp2bmRt496hwZ156G98vBmw8 /JuF7Au5iq7DuSBY/I+e09zh8WSCfWa3W3oU9BzEqZZm4WB/MweeATK1vQTCz3cD+f2f 8F0/D0p+V5uva++M0uldDrs5Fqw3h/PwPqW4fwzmo8UgVW6L00Yh2YMxrqoSKuxWjRzz XRhg== X-Gm-Message-State: AOAM533LIq9oGqQrfsL30QQobIn7Em1buIyQtDR7xW24TgbxKP1pg5oj eyiBBGy90/WBW6Xpt1lnyLsbUmJ/uTs/XYfNxEg= X-Google-Smtp-Source: ABdhPJyy9CNsu30l+dNSfn+J7Gf2sDm2Fw4sZNkYodDQwxk/JrQNOAtzD8TrxhnQ+oLtDAGEEJcjN/fKY2iWu4z6o+k= X-Received: by 2002:a25:3357:: with SMTP id z84mr237685ybz.260.1620240328981; Wed, 05 May 2021 11:45:28 -0700 (PDT) MIME-Version: 1.0 References: <20210505132529.401047-1-jolsa@kernel.org> In-Reply-To: <20210505132529.401047-1-jolsa@kernel.org> From: Andrii Nakryiko Date: Wed, 5 May 2021 11:45:17 -0700 Message-ID: Subject: Re: [PATCH] bpf: Forbid trampoline attach for functions with variable arguments To: Jiri Olsa Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Networking , bpf , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, May 5, 2021 at 6:42 AM Jiri Olsa wrote: > > We can't currently allow to attach functions with variable arguments. > The problem is that we should save all the registers for arguments, > which is probably doable, but if caller uses more than 6 arguments, > we need stack data, which will be wrong, because of the extra stack > frame we do in bpf trampoline, so we could crash. > > Also currently there's malformed trampoline code generated for such > functions at the moment as described in: > https://lore.kernel.org/bpf/20210429212834.82621-1-jolsa@kernel.org/ > > Signed-off-by: Jiri Olsa > --- LGTM. Acked-by: Andrii Nakryiko > kernel/bpf/btf.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c > index 0600ed325fa0..161511bb3e51 100644 > --- a/kernel/bpf/btf.c > +++ b/kernel/bpf/btf.c > @@ -5206,6 +5206,13 @@ int btf_distill_func_proto(struct bpf_verifier_log *log, > m->ret_size = ret; > > for (i = 0; i < nargs; i++) { > + if (i == nargs - 1 && args[i].type == 0) { > + bpf_log(log, > + "The function %s with variable args is unsupported.\n", > + tname); > + return -EINVAL; > + > + } > ret = __get_type_size(btf, args[i].type, &t); > if (ret < 0) { > bpf_log(log, > @@ -5213,6 +5220,12 @@ int btf_distill_func_proto(struct bpf_verifier_log *log, > tname, i, btf_kind_str[BTF_INFO_KIND(t->info)]); > return -EINVAL; > } > + if (ret == 0) { > + bpf_log(log, > + "The function %s has malformed void argument.\n", > + tname); > + return -EINVAL; > + } > m->arg_size[i] = ret; > } > m->nr_args = nargs; > -- > 2.30.2 >