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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 4DE84C54FD0 for ; Wed, 25 Mar 2020 14:35:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 13E4220777 for ; Wed, 25 Mar 2020 14:35:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="NSQNWZYg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727833AbgCYOfe (ORCPT ); Wed, 25 Mar 2020 10:35:34 -0400 Received: from mail-wm1-f67.google.com ([209.85.128.67]:36079 "EHLO mail-wm1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727501AbgCYOfe (ORCPT ); Wed, 25 Mar 2020 10:35:34 -0400 Received: by mail-wm1-f67.google.com with SMTP id g62so2965781wme.1 for ; Wed, 25 Mar 2020 07:35:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:date:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=4SCMfX4AFsAbSPoyRRB2akn3fbWQgwxVoxo/587s/z8=; b=NSQNWZYgH7h9i9bJ/0fpcGqR+VH3MsRrjjNKsBw/qMvHIVxROtE/7whq7UFq7v5S/z QrMRhJWkncsPtnhD/cQ9XRdOB6fwTXuvNhcCY3r0VvanFGk9LmguhT/S1HwmklbCSygS FPlzURZP+Wp0rut/CEkrX0IAIb1QiGU5LO2WI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to:user-agent; bh=4SCMfX4AFsAbSPoyRRB2akn3fbWQgwxVoxo/587s/z8=; b=F+WQDeM8hgcCARAHoUEW4PoNzjndy6lCjLn6gj+xAb9s3peuq9Fv7G8PA+o5mr3AIr HPNoJ73BX0TXH9oBzbENM9lSYqVliuQLFqLI8/ns7PSI8q0LmE9SnMa1BWmMZlYQfwOz s5/iza13mSrHbXRZ5XXgWKQE/w2c4VDRnr8SNUJEs2glkyl1B5VYmNzSSpc4PRZIdbCX FK0Iwyeh/bVdryJscxIJ5APCS2HgBCsfeVoZGCuuxVoSfSpg2LdMYD29bqe6PA9LxRId v6B6UgUXGYGD7r9ANoX7FhsJ5GSgQ63r+JW28gp6d8l269Dzvrx8wvUwWAb0rORpcyVf 0fPQ== X-Gm-Message-State: ANhLgQ00SqHPuSq5Fe4uE2tqdhb5FStL1oLLQuSrhBRjjcpcIxnOdiWM RZ9muL/qWseANsVLKKqO4jCYEQ== X-Google-Smtp-Source: ADFU+vtcbDNx2fH0BZ0dRVcQfoo8d+zdTI5b+qqCqcI7EqKovAvDaWAteq4zsCjG8Ks4n87sO3e5Aw== X-Received: by 2002:a05:600c:10ce:: with SMTP id l14mr3925012wmd.161.1585146932514; Wed, 25 Mar 2020 07:35:32 -0700 (PDT) Received: from chromium.org (77-56-209-237.dclient.hispeed.ch. [77.56.209.237]) by smtp.gmail.com with ESMTPSA id e9sm33653723wrw.30.2020.03.25.07.35.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Mar 2020 07:35:31 -0700 (PDT) From: KP Singh X-Google-Original-From: KP Singh Date: Wed, 25 Mar 2020 15:35:28 +0100 To: Kees Cook Cc: Casey Schaufler , linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, Brendan Jackman , Florent Revest , Alexei Starovoitov , Daniel Borkmann , James Morris , Paul Turner , Jann Horn , Florent Revest , Brendan Jackman , Greg Kroah-Hartman Subject: Re: [PATCH bpf-next v5 5/7] bpf: lsm: Initialize the BPF LSM hooks Message-ID: <20200325143528.GA22419@chromium.org> References: <20200323164415.12943-1-kpsingh@chromium.org> <20200323164415.12943-6-kpsingh@chromium.org> <202003231237.F654B379@keescook> <0655d820-4c42-cf9a-23d3-82dc4fdeeceb@schaufler-ca.com> <202003231354.1454ED92EC@keescook> <202003231505.59A11B06E@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <202003231505.59A11B06E@keescook> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 23-Mär 15:12, Kees Cook wrote: > On Mon, Mar 23, 2020 at 02:58:18PM -0700, Casey Schaufler wrote: > > That's not too terrible, I suppose. What would you be thinking for > > the calls that do use call_int_hook()? > > > > rc = call_int_hook(something, something_default, goodnesses); > > > > or embedded in the macro: > > > > rc = call_int_hook(something, goodnesses); > > Oh yes, good point. The hook call already knows the name, so: I learnt this the hard way that IRC that is passed to the call_int_hook macro is not the same as the default value for a hook call_int_hook accomdates for a different return value when no hook is implemented, but it does expect the default value of the hook to be 0 as it compares the return value of the callbacks to 0 instead of the default value whereas these special cases compare it with the default value. For example: If we define the default_value of the secid_to_secctx to -EOPNOTSUPP, it changes the behaviour and the BPF hook, which returns this default value always results in a failure. I noticed this when I saw a bunch of messages on my VM: audit: error in audit_log_task_context which comes from audit_log_task_context and calls security_secid_to_secctx which ends up being always denied by BPF. In anycase, I am still adding the default value in LSM_HOOK and using them in the following hooks: getprocattr -EINVAL inode_getsecurity -EOPNOTSUPP inode_setsecurity -EOPNOTSUPP setprocattr -EINVAL task_prctl -ENOSYS xfrm_state_pol_flow_match 1 Will send v6 out with these changes. - KP > > #define call_int_hook(FUNC, ...) ({ \ > int RC = FUNC#_default; \ > ... > > > -- > Kees Cook > >