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=-0.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,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 D1757C35646 for ; Fri, 21 Feb 2020 12:02:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A81E4222C4 for ; Fri, 21 Feb 2020 12:02:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="UKFOzCl6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728130AbgBUMCo (ORCPT ); Fri, 21 Feb 2020 07:02:44 -0500 Received: from mail-wr1-f65.google.com ([209.85.221.65]:44513 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726976AbgBUMCo (ORCPT ); Fri, 21 Feb 2020 07:02:44 -0500 Received: by mail-wr1-f65.google.com with SMTP id m16so1728663wrx.11 for ; Fri, 21 Feb 2020 04:02:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=XEMXcf1Qym5KZXe7M87kC8LbHamJQ0UMLSMngcLuhOU=; b=UKFOzCl6q4/cR/NsAjylHV5Gebfb6qxNZdL5rw1XT2ToRS3Q+BmEAaQt3KQowks3FV O2f4DMGkYVUc9KYLH3UeegG+7DhMaBXhBb8dvjuLIFosDhSaBHSmk3y0GcXVyKS00HDn CB3v4G6PN2dB9kj8W5qmjzuUQudPYm7QpNcUs= 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:user-agent; bh=XEMXcf1Qym5KZXe7M87kC8LbHamJQ0UMLSMngcLuhOU=; b=VwKPyw5v9lOPoZvgIo5Yx3MQGBY1gxMRu5gXCg0I5RQGiTq9IFYO7BRNckorkdcpg1 P/jFMZnlcM9vUXLult4SxX1clhaotjicnQ1wvMCdrRUojSTiAHmPKC4eiM9dbFFsbvu9 WCg84JnBYL7zKauWpdgi5hC4FI6PNzeTav3P/VpnqOKoW3vdQ3JtyyVt2/HSiBDO+Io7 jYSJhbpC2NR+70HHIigYATvpA5CBdHiF9pTkvDeFCf0UOTCOfBsxaJl12L6OlGCDZT9g 5IN70cAkx6TXv+CaCFAYFw4YKynkN3CPjXmyJZa4aMLdRONvFkgsvrjAMqahKAacdsc/ zF4A== X-Gm-Message-State: APjAAAW9BAOj/y3mz/8LP6yj3dY4TnIP5JN98xh3PIcK9Hk/n/iOVpV0 gCYlw45BG46mIWsyOE7Fw4QxCw== X-Google-Smtp-Source: APXvYqzsuM0rMnESdMtK5OBkUXp1jDKWa+okCPaVGYbgB20R7139xAB9Mq1tDbbjbEUGQCmxgxSxBQ== X-Received: by 2002:a5d:61cb:: with SMTP id q11mr50890228wrv.71.1582286562277; Fri, 21 Feb 2020 04:02:42 -0800 (PST) Received: from google.com ([2a00:79e0:42:204:8a21:ba0c:bb42:75ec]) by smtp.gmail.com with ESMTPSA id x21sm3322107wmi.30.2020.02.21.04.02.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Feb 2020 04:02:41 -0800 (PST) Date: Fri, 21 Feb 2020 13:02:40 +0100 From: KP Singh To: Alexei Starovoitov Cc: KP Singh , open list , bpf , Linux Security Module list , Daniel Borkmann , James Morris , Kees Cook , Jann Horn , "David S. Miller" , Greg Kroah-Hartman Subject: Re: [PATCH bpf-next v4 5/8] bpf: lsm: Implement attach, detach and execution Message-ID: References: <20200220175250.10795-1-kpsingh@chromium.org> <20200220175250.10795-6-kpsingh@chromium.org> <20200221021755.3z7ifyyeh6seo3zs@ast-mbp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200221021755.3z7ifyyeh6seo3zs@ast-mbp> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20-Feb 18:17, Alexei Starovoitov wrote: > On Thu, Feb 20, 2020 at 06:52:47PM +0100, KP Singh wrote: > > + > > + /* This is the first program to be attached to the LSM hook, the hook > > + * needs to be enabled. > > + */ > > + if (prog->type == BPF_PROG_TYPE_LSM && tr->progs_cnt[kind] == 1) > > + err = bpf_lsm_set_enabled(prog->aux->attach_func_name, true); > > out: > > mutex_unlock(&tr->mutex); > > return err; > > @@ -336,7 +348,11 @@ int bpf_trampoline_unlink_prog(struct bpf_prog *prog) > > } > > hlist_del(&prog->aux->tramp_hlist); > > tr->progs_cnt[kind]--; > > - err = bpf_trampoline_update(prog->aux->trampoline); > > + err = bpf_trampoline_update(prog); > > + > > + /* There are no more LSM programs, the hook should be disabled */ > > + if (prog->type == BPF_PROG_TYPE_LSM && tr->progs_cnt[kind] == 0) > > + err = bpf_lsm_set_enabled(prog->aux->attach_func_name, false); > > Overall looks good, but I don't think above logic works. > Consider lsm being attached, then fexit, then lsm detached, then fexit detached. > Both are kind==fexit and static_key stays enabled. You're right. I was weary of introducing a new kind (something like BPF_TRAMP_LSM) since they are just fexit trampolines. For now, I added nr_lsm_progs as a member in struct bpf_trampoline and refactored the increment and decrement logic into inline helper functions e.g. static inline void bpf_trampoline_dec_progs(struct bpf_prog *prog, enum bpf_tramp_prog_type kind) { struct bpf_trampoline *tr = prog->aux->trampoline; if (prog->type == BPF_PROG_TYPE_LSM) tr->nr_lsm_progs--; tr->progs_cnt[kind]--; } and doing the check as: if (prog->type == BPF_PROG_TYPE_LSM && tr->nr_lsm_progs == 0) err = bpf_lsm_set_enabled(prog->aux->attach_func_name, false); This should work, If you're okay with it, I will update it in the next revision of the patch-set. - KP