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=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 6A070C433E9 for ; Thu, 7 Jan 2021 22:31:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 47155235FF for ; Thu, 7 Jan 2021 22:31:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728521AbhAGWbb (ORCPT ); Thu, 7 Jan 2021 17:31:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47282 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728391AbhAGWb3 (ORCPT ); Thu, 7 Jan 2021 17:31:29 -0500 Received: from mail-ej1-x62f.google.com (mail-ej1-x62f.google.com [IPv6:2a00:1450:4864:20::62f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 31D18C0612F4 for ; Thu, 7 Jan 2021 14:30:49 -0800 (PST) Received: by mail-ej1-x62f.google.com with SMTP id d17so11883623ejy.9 for ; Thu, 07 Jan 2021 14:30:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=paul-moore-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=gAqEJZvOUVNx7GjAGJU4++QQQh5Iz2ZggF7mmYWr3jc=; b=bG+BCKd9SPDGkLBVmk9DWALKTJEta7jDlFUQrevNhzIflVRY1koxsH+dTANfkrr5hr UvMJ0eogDoUIQ2k7BkMHc3QD0V3DzolfWfdn9GHIVn1AaN69HmUcULw+LYobqPgZZMEB IB9WQeqvRxQV0J9Wo9qhbnimFNBY73T73CtH8aLBK5VUzlpJDLuWdOZFuamwHFfAzMPg JnaEpoNi15UuZmInclT+SDXs7Pn8znDMcK6VSggPKu9CSdZ5tpe907bI3nXZhjmo2OLd UMQJsbtWwdCJvYAwidna03bNfjP6zGlP5MhHLh4kroT6LSXu3BmCqOcyq4CoA8N7ha0G bSFA== 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=gAqEJZvOUVNx7GjAGJU4++QQQh5Iz2ZggF7mmYWr3jc=; b=OnlQhiuGv+89FIgkCgcTbojNlbx6061syawnfbaIZCBCbN29S565VbnOpQJzkUuabz 4zjtBUdwrNQkq3DENcGJjXKAQ9AeXmkbgcr1RhAG5PWnxcRMwiA8oxWfvW3jkfnZPduf gZ3B68xBLwIcrqH5Xakdwi9l73sXbZcfDxZnEvFBaSVJFJAqE0CB/rhkOki0/zVqOCQv 4OP0KeicwLjk7br8w9txzpJWwEthWakueB8EPwzZSYOMr1IajAk6l6MNbTvxa9lGLodj HxD+fx6taQTRinJTIul4AQf7htLk/ivX7KtomddOrs1D1k0bSpayF3Lcx4SVIaTBAdf+ IGmA== X-Gm-Message-State: AOAM531SIx2iZCONho7d3M/YKSOufEi8yuJpTYYboDC8w20jiGoFgUDL KANl3eHIVSlMinxQvLEiRSwAmpVFne5vV4zYQLFB X-Google-Smtp-Source: ABdhPJyFsPwDmA3L3Sh+WXq6NxfIuTJGbBAVParg9HTQzxnopUrkcfnjA+fzjgE75VQpmeAWCPgMnA/gFMROwpue71Q= X-Received: by 2002:a17:906:3712:: with SMTP id d18mr753300ejc.178.1610058647771; Thu, 07 Jan 2021 14:30:47 -0800 (PST) MIME-Version: 1.0 References: <20201112015359.1103333-1-lokeshgidra@google.com> <20201112015359.1103333-4-lokeshgidra@google.com> In-Reply-To: From: Paul Moore Date: Thu, 7 Jan 2021 17:30:36 -0500 Message-ID: Subject: Re: [PATCH v13 3/4] selinux: teach SELinux about anonymous inodes To: Lokesh Gidra Cc: Andrea Arcangeli , Alexander Viro , James Morris , Stephen Smalley , Casey Schaufler , Eric Biggers , "Serge E. Hallyn" , Eric Paris , Daniel Colascione , Kees Cook , "Eric W. Biederman" , KP Singh , David Howells , Anders Roxell , Sami Tolvanen , Matthew Garrett , Randy Dunlap , "Joel Fernandes (Google)" , YueHaibing , Christian Brauner , Alexei Starovoitov , Adrian Reber , Aleksa Sarai , Linux FS Devel , linux-kernel , LSM List , SElinux list , Kalesh Singh , Calin Juravle , Suren Baghdasaryan , Jeffrey Vander Stoep , "Cc: Android Kernel" , "open list:MEMORY MANAGEMENT" , Andrew Morton , hch@infradead.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 6, 2021 at 10:55 PM Lokesh Gidra wrote: > On Wed, Jan 6, 2021 at 7:03 PM Paul Moore wrote: > > On Wed, Nov 11, 2020 at 8:54 PM Lokesh Gidra wrote: > > > From: Daniel Colascione > > > > > > This change uses the anon_inodes and LSM infrastructure introduced in > > > the previous patches to give SELinux the ability to control > > > anonymous-inode files that are created using the new > > > anon_inode_getfd_secure() function. > > > > > > A SELinux policy author detects and controls these anonymous inodes by > > > adding a name-based type_transition rule that assigns a new security > > > type to anonymous-inode files created in some domain. The name used > > > for the name-based transition is the name associated with the > > > anonymous inode for file listings --- e.g., "[userfaultfd]" or > > > "[perf_event]". > > > > > > Example: > > > > > > type uffd_t; > > > type_transition sysadm_t sysadm_t : anon_inode uffd_t "[userfaultfd]"; > > > allow sysadm_t uffd_t:anon_inode { create }; > > > > > > (The next patch in this series is necessary for making userfaultfd > > > support this new interface. The example above is just > > > for exposition.) > > > > > > Signed-off-by: Daniel Colascione > > > Signed-off-by: Lokesh Gidra > > > --- > > > security/selinux/hooks.c | 56 +++++++++++++++++++++++++++++ > > > security/selinux/include/classmap.h | 2 ++ > > > 2 files changed, 58 insertions(+) > > > > > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > > > index 6b1826fc3658..d092aa512868 100644 > > > --- a/security/selinux/hooks.c > > > +++ b/security/selinux/hooks.c > > > @@ -2927,6 +2927,61 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir, > > > return 0; > > > } > > > > > > +static int selinux_inode_init_security_anon(struct inode *inode, > > > + const struct qstr *name, > > > + const struct inode *context_inode) > > > +{ > > > + const struct task_security_struct *tsec = selinux_cred(current_cred()); > > > + struct common_audit_data ad; > > > + struct inode_security_struct *isec; > > > + int rc; > > > + > > > + if (unlikely(!selinux_initialized(&selinux_state))) > > > + return 0; > > > + > > > + isec = selinux_inode(inode); > > > + > > > + /* > > > + * We only get here once per ephemeral inode. The inode has > > > + * been initialized via inode_alloc_security but is otherwise > > > + * untouched. > > > + */ > > > + > > > + if (context_inode) { > > > + struct inode_security_struct *context_isec = > > > + selinux_inode(context_inode); > > > + if (context_isec->initialized != LABEL_INITIALIZED) > > > + return -EACCES; > > > + > > > + isec->sclass = context_isec->sclass; > > > > Taking the object class directly from the context_inode is > > interesting, and I suspect problematic. In the case below where no > > context_inode is supplied the object class is set to > > SECCLASS_ANON_INODE, which is correct, but when a context_inode is > > supplied there is no guarantee that the object class will be set to > > SECCLASS_ANON_INODE. This could both pose a problem for policy > > writers (how do you distinguish the anon inode from other normal file > > inodes in this case?) as well as an outright fault later in this > > function when we try to check the ANON_INODE__CREATE on an object > > other than a SECCLASS_ANON_INODE object. > > > Thanks for catching this. I'll initialize 'sclass' unconditionally to > SECCLASS_ANON_INODE in the next version. Also, do you think I should > add a check that context_inode's sclass must be SECCLASS_ANON_INODE to > confirm that we never receive a regular inode as context_inode? This is one of the reasons why I was asking if you ever saw the need to use a regular inode here. It seems much safer to me to add a check to ensure that context_inode is SECCLASS_ANON_INODE and return an error otherwise; I would also suggest emitting an error using pr_err() with something along the lines of "SELinux: initializing anonymous inode with inappropriate inode" (or something similar). If something changes in the future we can always reconsider this restriction. > > It works in the userfaultfd case because the context_inode is > > originally created with this function so the object class is correctly > > set to SECCLASS_ANON_INODE, but can we always guarantee that to be the > > case? Do we ever need or want to support using a context_inode that > > is not SECCLASS_ANON_INODE? > > I don't think there is any requirement of supporting context_inode > which isn't anon-inode. And even if there is, as you described > earlier, for ANON_INODE__CREATE to work the sclass has to be > SECCLASS_ANON_INODE. I'll appreciate comments on this from others, > particularly Daniel and Stephen who originally discussed and > implemented this patch. I would encourage you not to wait too long for additional feedback before sending the next revision. -- paul moore www.paul-moore.com 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=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,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 7A13DC433E0 for ; Thu, 7 Jan 2021 22:30:51 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id EA238235FF for ; Thu, 7 Jan 2021 22:30:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EA238235FF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=paul-moore.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 38A796B0171; Thu, 7 Jan 2021 17:30:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 33C966B0172; Thu, 7 Jan 2021 17:30:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 22C1A8D0150; Thu, 7 Jan 2021 17:30:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0088.hostedemail.com [216.40.44.88]) by kanga.kvack.org (Postfix) with ESMTP id 0CF776B0171 for ; Thu, 7 Jan 2021 17:30:50 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id C0C00824556B for ; Thu, 7 Jan 2021 22:30:49 +0000 (UTC) X-FDA: 77680425018.16.boys43_0f16036274ed Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin16.hostedemail.com (Postfix) with ESMTP id A270B100E6903 for ; Thu, 7 Jan 2021 22:30:49 +0000 (UTC) X-HE-Tag: boys43_0f16036274ed X-Filterd-Recvd-Size: 9651 Received: from mail-ej1-f43.google.com (mail-ej1-f43.google.com [209.85.218.43]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Thu, 7 Jan 2021 22:30:49 +0000 (UTC) Received: by mail-ej1-f43.google.com with SMTP id d17so11883624ejy.9 for ; Thu, 07 Jan 2021 14:30:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=paul-moore-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=gAqEJZvOUVNx7GjAGJU4++QQQh5Iz2ZggF7mmYWr3jc=; b=bG+BCKd9SPDGkLBVmk9DWALKTJEta7jDlFUQrevNhzIflVRY1koxsH+dTANfkrr5hr UvMJ0eogDoUIQ2k7BkMHc3QD0V3DzolfWfdn9GHIVn1AaN69HmUcULw+LYobqPgZZMEB IB9WQeqvRxQV0J9Wo9qhbnimFNBY73T73CtH8aLBK5VUzlpJDLuWdOZFuamwHFfAzMPg JnaEpoNi15UuZmInclT+SDXs7Pn8znDMcK6VSggPKu9CSdZ5tpe907bI3nXZhjmo2OLd UMQJsbtWwdCJvYAwidna03bNfjP6zGlP5MhHLh4kroT6LSXu3BmCqOcyq4CoA8N7ha0G bSFA== 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=gAqEJZvOUVNx7GjAGJU4++QQQh5Iz2ZggF7mmYWr3jc=; b=onUI9pbXUx+c6f7RlneoInasw6CKBKn38MAUrbhkmg85IqkrD+XbSmDKtDQdwhgGkT 7NWkgc1b1xPCPcB0M67zBgc97fAbN+J8P/cid1Oo3C0uOvTJeEJF4Z+QjbSm7USy12pr LAfAkfAA7URkM42yBSYPyi+TfqY67DHVDU9CWDDayuao/ABARSJFnXnhklq64nl3vjOz HmtXExx/uTgGz1Gkoi8Ix+liYragMN47dcuVaWRMNkSy6eibcTjqVXSGo2G3MFDQAYQq uvDRr7+Ch7Hq8OxZd+R0UFggy8VmbPWQju/Sdw12PlFtOyJaL6vVwXu+yrHUtRBsAmmQ w3gw== X-Gm-Message-State: AOAM5307/bQH8mbhmUgWjIwYFdDBErjqTWlNpg/941sCoNVmKhfm5b74 tIxEiSOY2It0e1+ltD36Km0VKg7fjruQ4K2K01Rl X-Google-Smtp-Source: ABdhPJyFsPwDmA3L3Sh+WXq6NxfIuTJGbBAVParg9HTQzxnopUrkcfnjA+fzjgE75VQpmeAWCPgMnA/gFMROwpue71Q= X-Received: by 2002:a17:906:3712:: with SMTP id d18mr753300ejc.178.1610058647771; Thu, 07 Jan 2021 14:30:47 -0800 (PST) MIME-Version: 1.0 References: <20201112015359.1103333-1-lokeshgidra@google.com> <20201112015359.1103333-4-lokeshgidra@google.com> In-Reply-To: From: Paul Moore Date: Thu, 7 Jan 2021 17:30:36 -0500 Message-ID: Subject: Re: [PATCH v13 3/4] selinux: teach SELinux about anonymous inodes To: Lokesh Gidra Cc: Andrea Arcangeli , Alexander Viro , James Morris , Stephen Smalley , Casey Schaufler , Eric Biggers , "Serge E. Hallyn" , Eric Paris , Daniel Colascione , Kees Cook , "Eric W. Biederman" , KP Singh , David Howells , Anders Roxell , Sami Tolvanen , Matthew Garrett , Randy Dunlap , "Joel Fernandes (Google)" , YueHaibing , Christian Brauner , Alexei Starovoitov , Adrian Reber , Aleksa Sarai , Linux FS Devel , linux-kernel , LSM List , SElinux list , Kalesh Singh , Calin Juravle , Suren Baghdasaryan , Jeffrey Vander Stoep , "Cc: Android Kernel" , "open list:MEMORY MANAGEMENT" , Andrew Morton , hch@infradead.org Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jan 6, 2021 at 10:55 PM Lokesh Gidra wrote: > On Wed, Jan 6, 2021 at 7:03 PM Paul Moore wrote: > > On Wed, Nov 11, 2020 at 8:54 PM Lokesh Gidra wrote: > > > From: Daniel Colascione > > > > > > This change uses the anon_inodes and LSM infrastructure introduced in > > > the previous patches to give SELinux the ability to control > > > anonymous-inode files that are created using the new > > > anon_inode_getfd_secure() function. > > > > > > A SELinux policy author detects and controls these anonymous inodes by > > > adding a name-based type_transition rule that assigns a new security > > > type to anonymous-inode files created in some domain. The name used > > > for the name-based transition is the name associated with the > > > anonymous inode for file listings --- e.g., "[userfaultfd]" or > > > "[perf_event]". > > > > > > Example: > > > > > > type uffd_t; > > > type_transition sysadm_t sysadm_t : anon_inode uffd_t "[userfaultfd]"; > > > allow sysadm_t uffd_t:anon_inode { create }; > > > > > > (The next patch in this series is necessary for making userfaultfd > > > support this new interface. The example above is just > > > for exposition.) > > > > > > Signed-off-by: Daniel Colascione > > > Signed-off-by: Lokesh Gidra > > > --- > > > security/selinux/hooks.c | 56 +++++++++++++++++++++++++++++ > > > security/selinux/include/classmap.h | 2 ++ > > > 2 files changed, 58 insertions(+) > > > > > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > > > index 6b1826fc3658..d092aa512868 100644 > > > --- a/security/selinux/hooks.c > > > +++ b/security/selinux/hooks.c > > > @@ -2927,6 +2927,61 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir, > > > return 0; > > > } > > > > > > +static int selinux_inode_init_security_anon(struct inode *inode, > > > + const struct qstr *name, > > > + const struct inode *context_inode) > > > +{ > > > + const struct task_security_struct *tsec = selinux_cred(current_cred()); > > > + struct common_audit_data ad; > > > + struct inode_security_struct *isec; > > > + int rc; > > > + > > > + if (unlikely(!selinux_initialized(&selinux_state))) > > > + return 0; > > > + > > > + isec = selinux_inode(inode); > > > + > > > + /* > > > + * We only get here once per ephemeral inode. The inode has > > > + * been initialized via inode_alloc_security but is otherwise > > > + * untouched. > > > + */ > > > + > > > + if (context_inode) { > > > + struct inode_security_struct *context_isec = > > > + selinux_inode(context_inode); > > > + if (context_isec->initialized != LABEL_INITIALIZED) > > > + return -EACCES; > > > + > > > + isec->sclass = context_isec->sclass; > > > > Taking the object class directly from the context_inode is > > interesting, and I suspect problematic. In the case below where no > > context_inode is supplied the object class is set to > > SECCLASS_ANON_INODE, which is correct, but when a context_inode is > > supplied there is no guarantee that the object class will be set to > > SECCLASS_ANON_INODE. This could both pose a problem for policy > > writers (how do you distinguish the anon inode from other normal file > > inodes in this case?) as well as an outright fault later in this > > function when we try to check the ANON_INODE__CREATE on an object > > other than a SECCLASS_ANON_INODE object. > > > Thanks for catching this. I'll initialize 'sclass' unconditionally to > SECCLASS_ANON_INODE in the next version. Also, do you think I should > add a check that context_inode's sclass must be SECCLASS_ANON_INODE to > confirm that we never receive a regular inode as context_inode? This is one of the reasons why I was asking if you ever saw the need to use a regular inode here. It seems much safer to me to add a check to ensure that context_inode is SECCLASS_ANON_INODE and return an error otherwise; I would also suggest emitting an error using pr_err() with something along the lines of "SELinux: initializing anonymous inode with inappropriate inode" (or something similar). If something changes in the future we can always reconsider this restriction. > > It works in the userfaultfd case because the context_inode is > > originally created with this function so the object class is correctly > > set to SECCLASS_ANON_INODE, but can we always guarantee that to be the > > case? Do we ever need or want to support using a context_inode that > > is not SECCLASS_ANON_INODE? > > I don't think there is any requirement of supporting context_inode > which isn't anon-inode. And even if there is, as you described > earlier, for ANON_INODE__CREATE to work the sclass has to be > SECCLASS_ANON_INODE. I'll appreciate comments on this from others, > particularly Daniel and Stephen who originally discussed and > implemented this patch. I would encourage you not to wait too long for additional feedback before sending the next revision. -- paul moore www.paul-moore.com