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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 E4893C18E5A for ; Tue, 10 Mar 2020 18:25:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ADBDD208C3 for ; Tue, 10 Mar 2020 18:25:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WI9tLQJg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726692AbgCJSZV (ORCPT ); Tue, 10 Mar 2020 14:25:21 -0400 Received: from mail-oi1-f193.google.com ([209.85.167.193]:41485 "EHLO mail-oi1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726269AbgCJSZV (ORCPT ); Tue, 10 Mar 2020 14:25:21 -0400 Received: by mail-oi1-f193.google.com with SMTP id i1so14869735oie.8; Tue, 10 Mar 2020 11:25:21 -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=IjIWuou5FNbpKIwkRVi1r1E7TPmhuA9yxao2LdlFDVE=; b=WI9tLQJg7U6QlzllzIJHpD6wSvkR6y1ff62nPXosfhZyJsydo0PdyMGciqTChMwu2L Oeyn/jiioMtizwmrzehdCVIxILPScyEy//UJqoyqpjyBgQ4bxN77BJUZELrZMuIGYnE/ DRcAy4+vyqCWmO784Sc26Wz5AwMX5cbfSXi9YI2a+qslTFkjKXck0aqFJHIDOgI84NvM YjYBKH7u20RahkHVrddMtyGr/B8JLQ/UK7WOfnxQ+2x+rCfN1NnaPpk7YApJDiIcE1i1 Ngv8MuaOiP+XYfokKVE6/fcDTZ8ajiTUtvG5vm1eXYSSJnj+xIcfUM15NbtEFkMnGwER KA2A== 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=IjIWuou5FNbpKIwkRVi1r1E7TPmhuA9yxao2LdlFDVE=; b=NSoZ7tk7aHyn1RBMHZR86yF6wOwsJvXBjc6r5ysRtrS+xXiFTmcc07yb0fowdaF8eP yXHJYAcd/RVSFRBQTWtZscXu04vZGNH4qf+JwYtYYjOCsMnKEoIRzG3buocFzM9QrbF3 wnYjDW3CG8vf5p8HUIqIUhpdyoUuhjQFpKYWmmpSG8DOkrJ+YXGuFgkZxJMypsq+nc2Z 36jiHZSM5anWzndsfjzwzsGtBzRNID2/eEwswbrDTr3BS2dyHdLnTKc7ZjxR8AC2OVGI AkJLEix0RADHmXXRHK6t8C+zlx7qEsvONA2AavSDXlR3svR4Bt1924IsRyAzc4aqiZvM u9KQ== X-Gm-Message-State: ANhLgQ3Rx7c6ZrbhhWyLdd9/guBqDOlLvTnj/G+333/Rx33BsvYUMMox qZGF6RO5+d5mKbgc1HJ3KStfSFc1p4LDTXFvNdQ= X-Google-Smtp-Source: ADFU+vswVRn0x9/9vIuzC+gThOxIhkBVxwX9dq/qu0w55L1cDu/dEBQIkOIBCMOLoSPfrr4X2xbAcHrscbEUEr5kLJQ= X-Received: by 2002:aca:5191:: with SMTP id f139mr2210175oib.140.1583864720522; Tue, 10 Mar 2020 11:25:20 -0700 (PDT) MIME-Version: 1.0 References: <20200213194157.5877-1-sds@tycho.nsa.gov> In-Reply-To: From: Stephen Smalley Date: Tue, 10 Mar 2020 14:26:11 -0400 Message-ID: Subject: Re: [RFC PATCH] security,anon_inodes,kvm: enable security support for anon inodes To: Daniel Colascione Cc: Casey Schaufler , Sandeep Patil , Paul Moore , LSM List , Linux FS Devel , Al Viro , SElinux list , kvm@vger.kernel.org, Nick Kralevich , Stephen Smalley Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Mar 10, 2020 at 2:11 PM Daniel Colascione wrote: > > On Thu, Feb 20, 2020 at 10:50 AM Daniel Colascione wrote: > > > > On Thu, Feb 20, 2020 at 10:11 AM Casey Schaufler wrote: > > > > > > On 2/17/2020 4:14 PM, Paul Moore wrote: > > > > On Thu, Feb 13, 2020 at 2:41 PM Stephen Smalley wrote: > > > >> Add support for labeling and controlling access to files attached to anon > > > >> inodes. Introduce extended interfaces for creating such files to permit > > > >> passing a related file as an input to decide how to label the anon > > > >> inode. Define a security hook for initializing the anon inode security > > > >> attributes. Security attributes are either inherited from a related file > > > >> or determined based on some combination of the creating task and policy > > > >> (in the case of SELinux, using type_transition rules). As an > > > >> example user of the inheritance support, convert kvm to use the new > > > >> interface for passing the related file so that the anon inode can inherit > > > >> the security attributes of /dev/kvm and provide consistent access control > > > >> for subsequent ioctl operations. Other users of anon inodes, including > > > >> userfaultfd, will default to the transition-based mechanism instead. > > > >> > > > >> Compared to the series in > > > >> https://lore.kernel.org/selinux/20200211225547.235083-1-dancol@google.com/, > > > >> this approach differs in that it does not require creation of a separate > > > >> anonymous inode for each file (instead storing the per-instance security > > > >> information in the file security blob), it applies labeling and control > > > >> to all users of anonymous inodes rather than requiring opt-in via a new > > > >> flag, it supports labeling based on a related inode if provided, > > > >> it relies on type transitions to compute the label of the anon inode > > > >> when there is no related inode, and it does not require introducing a new > > > >> security class for each user of anonymous inodes. > > > >> > > > >> On the other hand, the approach in this patch does expose the name passed > > > >> by the creator of the anon inode to the policy (an indirect mapping could > > > >> be provided within SELinux if these names aren't considered to be stable), > > > >> requires the definition of type_transition rules to distinguish userfaultfd > > > >> inodes from proc inodes based on type since they share the same class, > > > >> doesn't support denying the creation of anonymous inodes (making the hook > > > >> added by this patch return something other than void is problematic due to > > > >> it being called after the file is already allocated and error handling in > > > >> the callers can't presently account for this scenario and end up calling > > > >> release methods multiple times), and may be more expensive > > > >> (security_transition_sid overhead on each anon inode allocation). > > > >> > > > >> We are primarily posting this RFC patch now so that the two different > > > >> approaches can be concretely compared. We anticipate a hybrid of the > > > >> two approaches being the likely outcome in the end. In particular > > > >> if support for allocating a separate inode for each of these files > > > >> is acceptable, then we would favor storing the security information > > > >> in the inode security blob and using it instead of the file security > > > >> blob. > > > > Bringing this back up in hopes of attracting some attention from the > > > > fs-devel crowd and Al. As Stephen already mentioned, from a SELinux > > > > perspective we would prefer to attach the security blob to the inode > > > > as opposed to the file struct; does anyone have any objections to > > > > that? > > > > > > Sorry for the delay - been sick the past few days. > > > > > > I agree that the inode is a better place than the file for information > > > about the inode. This is especially true for Smack, which uses > > > multiple extended attributes in some cases. I don't believe that any > > > except the access label will be relevant to anonymous inodes, but > > > I can imagine security modules with policies that would. > > > > > > I am always an advocate of full xattr support. It goes a long > > > way in reducing the number and complexity of special case interfaces. > > > > It sounds like we have broad consensus on using the inode to hold > > security information, implying that anon_inodes should create new > > inodes. Do any of the VFS people want to object? > > Ping? I'd recommend refreshing your patch series to incorporate feedback on the previous version and re-post, including viro and linux-fsdevel on the cc, and see if they have any comments on it.