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=-22.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 B4750C388F7 for ; Wed, 11 Nov 2020 03:30:24 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 230AD21D40 for ; Wed, 11 Nov 2020 03:30:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="qPqD9xJ1" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 230AD21D40 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 82EB26B0036; Tue, 10 Nov 2020 22:30:23 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 7B5EF6B005D; Tue, 10 Nov 2020 22:30:23 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 658D86B0068; Tue, 10 Nov 2020 22:30:23 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0226.hostedemail.com [216.40.44.226]) by kanga.kvack.org (Postfix) with ESMTP id 39B796B0036 for ; Tue, 10 Nov 2020 22:30:23 -0500 (EST) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id D30B4180AD80F for ; Wed, 11 Nov 2020 03:30:22 +0000 (UTC) X-FDA: 77470709484.21.gun54_430fe1e272fa Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin21.hostedemail.com (Postfix) with ESMTP id B543D180442C0 for ; Wed, 11 Nov 2020 03:30:22 +0000 (UTC) X-HE-Tag: gun54_430fe1e272fa X-Filterd-Recvd-Size: 12487 Received: from mail-il1-f194.google.com (mail-il1-f194.google.com [209.85.166.194]) by imf18.hostedemail.com (Postfix) with ESMTP for ; Wed, 11 Nov 2020 03:30:21 +0000 (UTC) Received: by mail-il1-f194.google.com with SMTP id x20so728573ilj.8 for ; Tue, 10 Nov 2020 19:30:21 -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=zoTFRJAIMA31qT21kOie4hLHdFOnrBP6JkMlSYwvnXI=; b=qPqD9xJ15agGALdrbfTaEKsO9t0BJdhVFUe0x+i7ee/umFU4twQYB7dWW8pPh8hIoY Dxwh3C++Z1NVuJzD5KbagTyBNBdcFW5EnhRdvStAUC0PQ0f3/bB6h3YTYRECqLvO676z QQi5TNwiPRsYz0ekahfr0ZOcjJLH/pU3Hcbae5v+YQKiHYoAF+HCDzkHzOZZ0/+94XJb gd6fd8edTbeAJ5n1o8PnO0PRi52I97T3hjuT8ZFjhQo68dZTqgu7j7avR32qPGQ3l1Pz HP+Cs/gv8tr/439GLUoD+Au86pHpxQ4lDLQlCVMEF/QIVX3Tmos2hm0/GIk3l/JEm+5l fplA== 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=zoTFRJAIMA31qT21kOie4hLHdFOnrBP6JkMlSYwvnXI=; b=b/ACyH0gZdtBKai02+9BNFQS8V1G1+0btPTR3y0+inKtzSsVqA7ywMg6ZgYUmZEUNv rxVPFmBEjdp3IrUwxvNSP+14u7L1XbQhHdQx5G7YxEriUJ3qJCklMXTLlkDStvaXGwzI +B0RNpY3/QPZcGfpj+xVlxv2F2cYSVY0NY6eFDE43dODpSq63NccSwwXpOivvLlB6tfu fusPde8yWPwqwkMX7wEgDqPDzNFgCGugzlKlnd10VBudyAJep1NwhUBRVpoGlA1WT58T AU/USquL7bIyrmOXwYm8swGoj896WJy9JyJnjocnkhSsfhmkMHSvhSYZsrxfAoFFiPRJ Y4Zw== X-Gm-Message-State: AOAM533qqsuCzM9HucZ+9qtdkkLcHG9bYWw9+CGOhl28HwTUf8pW2SK/ wV1nZ7DUWGSSYmDPr7rtmD/mcU919cqsR9yMX7XQ+A== X-Google-Smtp-Source: ABdhPJxK2Fi5zChFPjMF2Pn/NLuggjJUhsrqW9BIJNVd99uJhLXv9EktO5IEFPyPZvq0aC8iNVh/WmZqVika8Ky+Ta4= X-Received: by 2002:a92:8b4e:: with SMTP id i75mr14330378ild.43.1605065420914; Tue, 10 Nov 2020 19:30:20 -0800 (PST) MIME-Version: 1.0 References: <20201106155626.3395468-1-lokeshgidra@google.com> <20201106155626.3395468-4-lokeshgidra@google.com> In-Reply-To: From: Lokesh Gidra Date: Tue, 10 Nov 2020 19:30:09 -0800 Message-ID: Subject: Re: [PATCH v12 3/4] selinux: teach SELinux about anonymous inodes To: Paul Moore 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 , Thomas Cedeno , Anders Roxell , Sami Tolvanen , Matthew Garrett , Aaron Goidel , Randy Dunlap , "Joel Fernandes (Google)" , YueHaibing , Christian Brauner , Alexei Starovoitov , Alexey Budankov , Adrian Reber , Aleksa Sarai , Linux FS Devel , linux-kernel , LSM List , SElinux list , Kalesh Singh , Calin Juravle , Suren Baghdasaryan , Nick Kralevich , Jeffrey Vander Stoep , "Cc: Android Kernel" , "open list:MEMORY MANAGEMENT" , Andrew Morton , hch@infradead.org, Daniel Colascione 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 Tue, Nov 10, 2020 at 6:13 PM Paul Moore wrote: > > On Tue, Nov 10, 2020 at 1:24 PM Lokesh Gidra wrote: > > On Mon, Nov 9, 2020 at 7:12 PM Paul Moore wrote: > > > On Fri, Nov 6, 2020 at 10:56 AM 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 | 53 +++++++++++++++++++++++++++++ > > > > security/selinux/include/classmap.h | 2 ++ > > > > 2 files changed, 55 insertions(+) > > > > > > > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > > > > index 6b1826fc3658..1c0adcdce7a8 100644 > > > > --- a/security/selinux/hooks.c > > > > +++ b/security/selinux/hooks.c > > > > @@ -2927,6 +2927,58 @@ 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); > > > > + isec->sclass = context_isec->sclass; > > > > + isec->sid = context_isec->sid; > > > > > > I suppose this isn't a major concern given the limited usage at the > > > moment, but I wonder if it would be a good idea to make sure the > > > context_inode's SELinux label is valid before we assign it to the > > > anonymous inode? If it is invalid, what should we do? Do we attempt > > > to (re)validate it? Do we simply fallback to the transition approach? > > > > Frankly, I'm not too familiar with SELinux. Originally this patch > > series was developed by Daniel, in consultation with Stephen Smalley. > > In my (probably naive) opinion we should fallback to transition > > approach. But I'd request you to tell me if this needs to be addressed > > now, and if so then what's the right approach. > > > > If the decision is to address this now, then what's the best way to > > check the SELinux label validity? > > You can check to see if an inode's label is valid by looking at the > isec->initialized field; if it is LABEL_INITIALIZED then it is all > set, if it is any other value then the label isn't entirely correct. > It may have not have ever been fully initialized (and has a default > value) or it may have live on a remote filesystem where the host has > signaled that the label has changed (and the label is now outdated). > > This patchset includes support for userfaultfd, which means we don't > really have to worry about the remote fs problem, but the > never-fully-initialized problem could be real in this case. Normally > we would revalidate an inode in SELinux by calling > __inode_security_revalidate() which requires either a valid dentry or > one that can be found via the inode; does d_find_alias() work on > userfaultfd inodes? > > If all else fails, it seems like the safest approach would be to > simply fail the selinux_inode_init_security_anon() call if a > context_inode was supplied and the label wasn't valid. If we later > decide to change it to falling back to the transition approach we can > do that, we can't go the other way (from transition to error). > I'm not sure about d_find_alias() on userfaultfd inodes. But it seems ok to fail selinux_inode_init_security_anon() to begin with. > > > > + } else { > > > > + isec->sclass = SECCLASS_ANON_INODE; > > > > + rc = security_transition_sid( > > > > + &selinux_state, tsec->sid, tsec->sid, > > > > + isec->sclass, name, &isec->sid); > > > > + if (rc) > > > > + return rc; > > > > + } > > > > + > > > > + isec->initialized = LABEL_INITIALIZED; > > > > + > > > > + /* > > > > + * Now that we've initialized security, check whether we're > > > > + * allowed to actually create this type of anonymous inode. > > > > + */ > > > > + > > > > + ad.type = LSM_AUDIT_DATA_INODE; > > > > + ad.u.inode = inode; > > > > + > > > > + return avc_has_perm(&selinux_state, > > > > + tsec->sid, > > > > + isec->sid, > > > > + isec->sclass, > > > > + FILE__CREATE, > > > > > > I believe you want to use ANON_INODE__CREATE here instead of FILE__CREATE, yes? > > > > ANON_INODE__CREATE definitely seems more appropriate. I'll change it > > in the next revision. > > > > > This brings up another question, and requirement - what testing are > > > you doing for this patchset? We require that new SELinux kernel > > > functionality includes additions to the SELinux test suite to help > > > verify the functionality. I'm also *strongly* encouraging that new > > > contributions come with updates to The SELinux Notebook. If you are > > > unsure about what to do for either, let us know and we can help get > > > you started. > > > > > > * https://github.com/SELinuxProject/selinux-testsuite > > > * https://github.com/SELinuxProject/selinux-notebook > > > > > I'd definitely need help with both of these. Kindly guide how to proceed. > > Well, perhaps the best way to start is to explain how you have been > testing this so far and then using that information to draft a test > for the testsuite. > As I said in my previous reply, Daniel worked on this patch along with Stephan Smalley. Here's the conversation regarding testing from back then: https://lore.kernel.org/lkml/CAEjxPJ4iquFSBfEj+UEFLUFHPsezuQ-Bzv09n+WgOWk38Nyw3w@mail.gmail.com/ There have been only minor changes (fixing comments/coding-style), except for addressing a double free issue with userfaultfd_ctx since last time it was tested as per the link above. > -- > paul moore > www.paul-moore.com