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=-28.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 04ECFC63798 for ; Wed, 18 Nov 2020 22:39:59 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4CC76246E4 for ; Wed, 18 Nov 2020 22:39:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="CRZIVIaW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4CC76246E4 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 7DBB16B005D; Wed, 18 Nov 2020 17:39:57 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 7B32B6B0068; Wed, 18 Nov 2020 17:39:57 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6C8FB6B006C; Wed, 18 Nov 2020 17:39:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0059.hostedemail.com [216.40.44.59]) by kanga.kvack.org (Postfix) with ESMTP id 391F36B005D for ; Wed, 18 Nov 2020 17:39:57 -0500 (EST) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id C56623635 for ; Wed, 18 Nov 2020 22:39:56 +0000 (UTC) X-FDA: 77499007992.01.juice56_05069412733d Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin01.hostedemail.com (Postfix) with ESMTP id A473F1004DAA0 for ; Wed, 18 Nov 2020 22:39:56 +0000 (UTC) X-HE-Tag: juice56_05069412733d X-Filterd-Recvd-Size: 17300 Received: from mail-ed1-f68.google.com (mail-ed1-f68.google.com [209.85.208.68]) by imf14.hostedemail.com (Postfix) with ESMTP for ; Wed, 18 Nov 2020 22:39:56 +0000 (UTC) Received: by mail-ed1-f68.google.com with SMTP id t9so3744691edq.8 for ; Wed, 18 Nov 2020 14:39:55 -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=mh4Qjzb8KLSgaMNmAYGectlp/+Zs2oISPb70IoHgsI8=; b=CRZIVIaWJn4wRTqExaJYLXqnr5OhuX/Ux33O/CKOWLZw+6wBPmuXEyiSTB3fn/OuoB 5W7kGYZwmmLIjODlbM1WZgo/01YuAEr0CtnFBOV16R4EfITvzzkyEd8XO075r/UTcJt+ zImZ+g75iGdxnhvDVM6/d6dyWVqZMgivbYHNHtVo27ZrWnAK7egyTI5flEh2L5o1F2Zc peaGWkXGnNSPGL/j6sgFZiGnhQ62hcV06/KYWEuTYsZJEskQEaXB7Wp4YlAEe9vWwqY0 c1fiNV9lk1053jw3Yucz8Rp5fk4RAcK6rlIp9pJBUHkJ5EJFsKuW0LiA8cZKrqaYTwhn yh5w== 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=mh4Qjzb8KLSgaMNmAYGectlp/+Zs2oISPb70IoHgsI8=; b=huz5YCi5RbOZNeavFRId92IqAu20ot1oIj3D+646YGGtqSWbBKBQ7PJPIJksNqlqFP c3OaJMZ5WLhx9MckjCiWKgFHSJvI0FGvFxK78hP2K7QukN4hrGfMxisHqtcdSeynfOlE mQDf8NtYBNgIXLfdmiNdFtJvoNnMGvNbpgIaGh9rdbBfpDxKsnIO2vwRl7uwMoNslZud lMkaxE9XwPr0pzQu+pEbGL7YbzMNmFtrLIece/nr/t9ud5cRrzemrlAJMjekO0Uf/Nbl g4Z+rUpLlEj9HegzRhRM57isXUo4Vp8bgUy8isBrKkYuy3bhD2wTfuxzzM4jw/ocnScD f1mA== X-Gm-Message-State: AOAM530fCVe++uquTW7sqKHj9KY8L+WX/kWYYuHXn/2dDWgUlgLrCpGO Qc9Qx958lmEa6ZLN7XiM5CD/55wu91t7UfaJkBsklA== X-Google-Smtp-Source: ABdhPJwQhDxciSRkAl2VxK0vZnAeNRN4fgcGI2LnmSEZCHTKqJlvVqW32Uzql9y2c4OzJjhY30YrLxWXujyaeuTcCCU= X-Received: by 2002:aa7:c704:: with SMTP id i4mr27725768edq.51.1605739194344; Wed, 18 Nov 2020 14:39:54 -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: Wed, 18 Nov 2020 14:39:42 -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 , Jeffrey Vander Stoep , "Cc: Android Kernel" , "open list:MEMORY MANAGEMENT" , Andrew Morton , hch@infradead.org Content-Type: multipart/mixed; boundary="00000000000048c66905b4694aa9" 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: --00000000000048c66905b4694aa9 Content-Type: text/plain; charset="UTF-8" On Thu, Nov 12, 2020 at 4:13 PM Paul Moore wrote: > > On Tue, Nov 10, 2020 at 10:30 PM Lokesh Gidra wrote: > > 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. > > I'm okay with simply failing here, but I'm growing a bit concerned > that this patchset hasn't been well tested. That is a problem. > > > > > > 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. > > I should probably be more clear. I honestly don't care who originally > wrote the patch, the simple fact is that you are the one who is > posting it *now* for inclusion in the kernel; at the very least I > expect you to be able to demonstrate that you are able to reliably > test this functionality and prove it is working. While being able to > test this submission initially is important, it is far more important > to have the tests and docs necessary to maintain this functionality > long term. Perhaps you and/or Google will continue to contribute and > support this functionality long term, but it would be irresponsible of > me to assume that to be true; both people and companies come and go > but code has a tendency to live forever. > > Let's start again; how have you been testing this code? > I have created a cuttlefish build and have tested with the attached userfaultfd program: 1) Without these kernel patches the program executes without any restrictions vsoc_x86_64:/ $ ./system/bin/userfaultfdSimple api: 170 features: 511 ioctls: 9223372036854775811 read: Try again 2) With these patches applied but without any policy the 'permission denied' is thrown vsoc_x86_64:/ $ ./system/bin/userfaultfdSimple syscall(userfaultfd): Permission denied with the following logcat message: 11-18 14:21:44.041 3130 3130 W userfaultfdSimp: type=1400 audit(0.0:107): avc: denied { create } for dev="anon_inodefs" ino=45031 scontext=u:r:shell:s0 tcontext=u:object_r:shell:s0 tclass=anon_inode permissive=0 3) With the attached .te policy file in place the following output is observed, confirming that the patch is working as intended. vsoc_x86_64:/ $ ./vendor/bin/userfaultfdSimple UFFDIO_API: Permission denied with the following logcat message: 11-18 14:33:29.142 2028 2028 W userfaultfdSimp: type=1400 audit(0.0:104): avc: denied { ioctl } for path="anon_inode:[userfaultfd]" dev="anon_inodefs" ino=41169 ioctlcmd=0xaa3f scontext=u:r:userfaultfdSimple:s0 tcontext=u:object_r:uffd_t:s0 tclass=anon_inode permissive=0 > -- > paul moore > www.paul-moore.com --00000000000048c66905b4694aa9 Content-Type: text/x-c++src; charset="US-ASCII"; name="userfaultfd_simple.cc" Content-Disposition: attachment; filename="userfaultfd_simple.cc" Content-Transfer-Encoding: base64 Content-ID: X-Attachment-Id: f_khnyhxjz0 I2luY2x1ZGUgPHN0ZGlvLmg+CiNpbmNsdWRlIDxmY250bC5oPgojaW5jbHVkZSA8dW5pc3RkLmg+ CiNpbmNsdWRlIDxjc3RyaW5nPgoKI2luY2x1ZGUgPHN5cy90eXBlcy5oPgojaW5jbHVkZSA8c3lz L2lvY3RsLmg+CiNpbmNsdWRlIDxzeXMvc3lzY2FsbC5oPgoKI2luY2x1ZGUgPGxpbnV4L3VzZXJm YXVsdGZkLmg+Cgp2b2lkIHByaW50X2FwaShjb25zdCBzdHJ1Y3QgdWZmZGlvX2FwaSAqYXBpKQp7 CglwcmludGYoImFwaTogJWxsdVxuIiwgYXBpLT5hcGkpOwoJcHJpbnRmKCJmZWF0dXJlczogJWxs dVxuIiwgYXBpLT5mZWF0dXJlcyk7CglwcmludGYoImlvY3RsczogJWxsdVxuIiwgYXBpLT5pb2N0 bHMpOwoKCXByaW50ZigiXG4iKTsKfQoKaW50IG1haW4odm9pZCkKewoJbG9uZyB1ZmZkID0gc3lz Y2FsbChfX05SX3VzZXJmYXVsdGZkLCBPX0NMT0VYRUMgfCBPX05PTkJMT0NLKTsKCWlmICh1ZmZk IDwgMCkgewoJCXBlcnJvcigic3lzY2FsbCh1c2VyZmF1bHRmZCkiKTsKCQlyZXR1cm4gLTE7Cgl9 CgoJc3RydWN0IHVmZmRpb19hcGkgYXBpOwoJc3RkOjptZW1zZXQoJmFwaSwgMHgwLCBzaXplb2Yg YXBpKTsKCWFwaS5hcGkgPSBVRkZEX0FQSTsKCWlmIChpb2N0bCh1ZmZkLCBVRkZESU9fQVBJLCAm YXBpKSA8IDApIHsKCQlwZXJyb3IoIlVGRkRJT19BUEkiKTsKCQlyZXR1cm4gLTE7Cgl9CgoJcHJp bnRfYXBpKCZhcGkpOwoKCXN0cnVjdCB1ZmZkX21zZyBtc2c7CglzdGQ6Om1lbXNldCgmbXNnLCAw eDAsIHNpemVvZiBtc2cpOwoJc3NpemVfdCBjb3VudCA9IHJlYWQodWZmZCwgJm1zZywgc2l6ZW9m KG1zZykpOwoJaWYgKGNvdW50IDwgMCkgewoJCXBlcnJvcigicmVhZCIpOwoJCXJldHVybiAtMTsK CX0gZWxzZSBpZiAoY291bnQgPT0gMCkgewoJCXByaW50ZigicmVhZCBFT0ZcblxuIik7Cgl9CgoJ cHJpbnRmKCJyZWFkIHVmZmRcblxuIik7CgoJcmV0dXJuIDA7Cn0K --00000000000048c66905b4694aa9 Content-Type: application/octet-stream; name="userfaultfdSimple.te" Content-Disposition: attachment; filename="userfaultfdSimple.te" Content-Transfer-Encoding: base64 Content-ID: X-Attachment-Id: f_khnziydf1 CnR5cGUgdXNlcmZhdWx0ZmRTaW1wbGUsIGRvbWFpbjsKCnR5cGUgdXNlcmZhdWx0ZmRTaW1wbGVf ZXhlYywgdmVuZG9yX2ZpbGVfdHlwZSwgZXhlY190eXBlLCBmaWxlX3R5cGU7Cgp0eXBlIHVmZmRf dDsKdHlwZV90cmFuc2l0aW9uIHVzZXJmYXVsdGZkU2ltcGxlIHVzZXJmYXVsdGZkU2ltcGxlIDog YW5vbl9pbm9kZSB1ZmZkX3QgIlt1c2VyZmF1bHRmZF0iOwphbGxvdyB1c2VyZmF1bHRmZFNpbXBs ZSB1ZmZkX3Q6YW5vbl9pbm9kZSB7IGNyZWF0ZSBpb2N0bCByZWFkIH07CgojIFVuY29tbWVudCBv bmUgb2YgdGhlIGFsbG93eCBsaW5lcyBiZWxvdyB0byB0ZXN0IGlvY3RsIHdoaXRlbGlzdGluZy4K IyBOb25lCmFsbG93eHBlcm0gdXNlcmZhdWx0ZmRTaW1wbGUgdWZmZF90OmFub25faW5vZGUgaW9j dGwgMHgwOwojIFVGRkRJT19BUEkKI2FsbG93eHBlcm0gdXNlcmZhdWx0ZmRTaW1wbGUgdWZmZF90 OmFub25faW5vZGUgaW9jdGwgMHhhYTNmOwoKZG9udGF1ZGl0IHVzZXJmYXVsdGZkU2ltcGxlIGFk YmQ6ZmQgdXNlOwpkb250YXVkaXQgdXNlcmZhdWx0ZmRTaW1wbGUgYWRiZDp1bml4X3N0cmVhbV9z b2NrZXQgeyByZWFkIHdyaXRlIH07CmRvbnRhdWRpdCB1c2VyZmF1bHRmZFNpbXBsZSBkZXZwdHM6 Y2hyX2ZpbGUgeyBnZXRhdHRyIGlvY3RsIHJlYWQgd3JpdGUgfTsKZG9udGF1ZGl0IHVzZXJmYXVs dGZkU2ltcGxlIHNoZWxsOmZkIHVzZTsKCmRvbWFpbl9hdXRvX3RyYW5zKHNoZWxsLCB1c2VyZmF1 bHRmZFNpbXBsZV9leGVjLCB1c2VyZmF1bHRmZFNpbXBsZSk7Cg== --00000000000048c66905b4694aa9--