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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 EE084C11D19 for ; Thu, 20 Feb 2020 18:50:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CB52124673 for ; Thu, 20 Feb 2020 18:50:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="QSbi426X" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728400AbgBTSux (ORCPT ); Thu, 20 Feb 2020 13:50:53 -0500 Received: from mail-lj1-f195.google.com ([209.85.208.195]:37314 "EHLO mail-lj1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728383AbgBTSuw (ORCPT ); Thu, 20 Feb 2020 13:50:52 -0500 Received: by mail-lj1-f195.google.com with SMTP id q23so5357212ljm.4 for ; Thu, 20 Feb 2020 10:50:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=qT0+tJ3JfMm/Au3fd6jXh7TStZpW/jP0WQ11tC4BoO0=; b=QSbi426XGCNQQMRZ6i9wp2Hxt1rja/L/DmV64pQlAZ/xexjWOLYpyMkZcTtHbV2RTj boUMY9a0RzdRBTzrdsifBJ0B2eba3N31tLklsMXFXu40xW+SLB0sh63csfs0l7Pq6TQw 8Y39T/oAj/FZSyrExUPgGcQiPy763ExfZ40o78eNKqrwWokvsfH2BLJQRI9egP3gqaF7 ZNpq+u1zDdOG6KaeTGDil/ZKOY3lyIStYyNcDZvIZsvNOZbkZezrkmUH8nVvS4HQS7j2 +TgkCh/8WDvP/c9Fn+ktQ2uyzzQnAmOn9JkRC7NaW/t/XmSQFYuHjt7yGggX5MzF2cZJ dmdA== 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=qT0+tJ3JfMm/Au3fd6jXh7TStZpW/jP0WQ11tC4BoO0=; b=P8k+hK5zOsSA/fTm0doqk0+EXHAlVkvjLhQaIyC2s/NPMsAG4IoJ3EPnAL+SsjISl4 DYrovpMa6jxhtkFWuQwFtJfuQCNnggJ0oE7gt4HJj9+37xnyXb4bnI9PyVOMhgr2IZQc ANGBFUKStu2F5URm4TzCS6jtMFhEGxvE6ADZcJg1fjHvLhdwYwY4XIDk0DBWo2mM+lL1 ckRABAjfPdnCwiL5hXwoeDZcqZ9i5jJ73BMTBdV4k3s0smgGqaXXFu4Y+GmQHksv4wDy B30z1yS6kAaYVNudxruYB93t9uWc1eQUsrF/3BFPZY/oSfHL84cu39YuaMdydXFAy9/b t+fA== X-Gm-Message-State: APjAAAUZjSs6FEp1luTYB11HTAs+4ZWnC4He91+1KzHGvTI+CB1uUO7b h08PVX4Y2rs9njZrKZ8QoAeeAVALf/hb64Fx3UnqHN8c X-Google-Smtp-Source: APXvYqzsRgrvQVx3QKNJYHllLg9vf16d6MXdzUk6Ci3jAbHoIgsX8JWZFkYTVZcMNn0E/OKk18FpGWonj/U+Lm67ni0= X-Received: by 2002:a2e:9284:: with SMTP id d4mr19204328ljh.226.1582224649152; Thu, 20 Feb 2020 10:50:49 -0800 (PST) MIME-Version: 1.0 References: <20200213194157.5877-1-sds@tycho.nsa.gov> In-Reply-To: From: Daniel Colascione Date: Thu, 20 Feb 2020 10:50:12 -0800 Message-ID: Subject: Re: [RFC PATCH] security,anon_inodes,kvm: enable security support for anon inodes To: Casey Schaufler Cc: 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 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?