From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Casey Schaufler <casey@schaufler-ca.com>
Cc: Dmitry Vyukov <dvyukov@google.com>,
Paul Moore <paul@paul-moore.com>,
Stephen Smalley <sds@tycho.nsa.gov>,
syzbot <syzbot+21016130b0580a9de3b5@syzkaller.appspotmail.com>,
tyhicks@canonical.com,
John Johansen <john.johansen@canonical.com>,
James Morris <jmorris@namei.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-security-module@vger.kernel.org,
Serge Hallyn <serge@hallyn.com>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
Jeffrey Vander Stoep <jeffv@google.com>,
SELinux <selinux@vger.kernel.org>,
Russell Coker <russell@coker.com.au>,
Laurent Bigonville <bigon@debian.org>,
syzkaller <syzkaller@googlegroups.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] LSM: Allow syzbot to ignore security= parameter.
Date: Thu, 07 Feb 2019 11:30:30 +0900 [thread overview]
Message-ID: <201902070230.x172UUG6002087@www262.sakura.ne.jp> (raw)
In-Reply-To: <0d23d1a5-d4af-debf-6b5f-aaaf698daaa8@schaufler-ca.com>
Casey Schaufler wrote:
> On 2/6/2019 2:23 AM, Tetsuo Handa wrote:
> > But as I update the documentation ( https://tomoyo.osdn.jp/2.6/chapter-3.html.en#3.6 ),
> > I came to think that we should ignore security= parameter when lsm= parameter is specified.
> >
> > Currently, it is possible to enable TOMOYO and only one of SELinux/Smack/AppArmor. Therefore,
> > it is possible to disable only TOMOYO by specifying security=selinux when we want to enable
> > only SELinux, by specifying security=smack when we want to enable only Smack, by specifying
> > security=apparmor when we want to enable only AppArmor. That is, we can use security= parameter
> > in order to specify the other LSM module which should not be disabled.
> >
> > But when it becomes possible to enable TOMOYO and more than one of SELinux/Smack/AppArmor,
> > we will no longer be able to selectively disable one LSM module using security= parameter, for
> > security= parameter is intended for specifying only one LSM module which should be enabled.
> > That is, we will need to use lsm= parameter in order to selectively disable LSM modules.
>
> Yes. That is correct. The existing behavior of security= is maintained.
But the existing behavior of CONFIG_DEFAULT_SECURITY is not maintained.
This might cause a problem like
commit e5a3b95f581da62e2054ef79d3be2d383e9ed664
Author: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Sat Feb 14 11:46:56 2009 +0900
TOMOYO: Don't create securityfs entries unless registered.
TOMOYO should not create /sys/kernel/security/tomoyo/ interface unless
TOMOYO is registered.
for Ubuntu users because Ubuntu kernels are built with
CONFIG_SECURITY_SELINUX=y
CONFIG_SECURITY_SMACK=y
CONFIG_SECURITY_TOMOYO=y
CONFIG_SECURITY_APPARMOR=y
CONFIG_SECURITY_YAMA=y
CONFIG_DEFAULT_SECURITY="apparmor"
. Due to CONFIG_DEFAULT_SECURITY="apparmor", majority of Ubuntu users are enabling
only AppArmor without explicitly specifying "security=apparmor".
Currently default CONFIG_LSM setting is
"yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor"
but Ubuntu kernels would have to be built with non-default CONFIG_LSM setting like
"yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo"
in order to make sure that AppArmor is by default chosen for the LSM_FLAG_EXCLUSIVE module.
Now that TOMOYO becomes a !LSM_FLAG_EXCLUSIVE module, not specifying "security=apparmor" will
automatically enable TOMOYO. And majority of Ubuntu users will unexpectedly encounter TOMOYO
messages. But removing "tomoyo" from CONFIG_LSM setting in order to save majority of Ubuntu
users from unexpectedly encountering TOMOYO messages also has a problem; Ubuntu users who want
to enable only TOMOYO from LSM_FLAG_LEGACY_MAJOR modules can specify "security=tomoyo", but
Ubuntu users who want to enable TOMOYO and one of SELinux,Smack,AppArmor (including syzbot)
will have to explicitly specify "lsm=" because "security=" can't allow enabling multiple
LSM_FLAG_LEGACY_MAJOR modules.
> The new behavior of lsm= is provided to allow general handling of a list
> of security modules. It uses the same form of data as CONFIG_LSM.
>
> > Then, I think that it is straightforward (and easier to manage) to ignore security= parameter
> > when lsm= parameter is specified.
>
> That reduces flexibility somewhat. If I am debugging security modules
> I may want to use lsm= to specify the order while using security= to
> identify a specific exclusive module. I could do that using lsm= by
> itself, but habits die hard.
"lsm=" can be used for identifying a specific exclusive module, and Ubuntu kernels would
have to use CONFIG_LSM (or "lsm=") for identifying the default exclusive module (in order
to allow enabling both TOMOYO and one of SELinux,Smack,AppArmor at the same time).
Since "security=" can't be used for selectively enable/disable more than one of
SELinux,Smack,TOMOYO,AppArmor, I think that recommending users to migrate to "lsm=" is the
better direction. And ignoring "security=" when "lsm=" is specified is easier to understand.
next prev parent reply other threads:[~2019-02-07 2:31 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-30 2:17 WARNING in apparmor_secid_to_secctx syzbot
2018-08-30 2:21 ` Dmitry Vyukov
2018-08-31 16:03 ` Stephen Smalley
2018-08-31 16:07 ` Paul Moore
2018-08-31 16:16 ` Stephen Smalley
2018-08-31 16:17 ` Stephen Smalley
2018-08-31 22:38 ` Dmitry Vyukov
2018-09-04 12:57 ` Stephen Smalley
2018-09-04 13:16 ` Russell Coker
2018-09-04 14:53 ` Dmitry Vyukov
2018-09-05 17:13 ` Kees Cook
2018-09-04 15:02 ` Dmitry Vyukov
2018-09-04 15:28 ` Stephen Smalley
2018-09-04 15:38 ` Dmitry Vyukov
2018-09-04 17:02 ` Stephen Smalley
2018-09-05 1:21 ` Paul Moore
2018-09-05 11:08 ` Dmitry Vyukov
2018-09-05 17:37 ` Casey Schaufler
2018-09-06 10:59 ` Dmitry Vyukov
2018-09-06 11:19 ` Dmitry Vyukov
2018-09-06 19:35 ` Dmitry Vyukov
2019-01-29 11:32 ` Tetsuo Handa
2019-01-30 14:45 ` Dmitry Vyukov
2019-01-30 16:30 ` Micah Morton
2019-01-31 0:22 ` Tetsuo Handa
2019-02-01 10:09 ` Dmitry Vyukov
2019-02-01 10:11 ` Dmitry Vyukov
2019-02-01 10:43 ` Tetsuo Handa
2019-02-01 10:50 ` Dmitry Vyukov
2019-02-01 13:09 ` [PATCH] LSM: Allow syzbot to ignore security= parameter Tetsuo Handa
2019-02-04 8:07 ` Dmitry Vyukov
2019-02-06 10:23 ` Tetsuo Handa
2019-02-06 17:03 ` Casey Schaufler
2019-02-07 2:30 ` Tetsuo Handa [this message]
2019-02-07 16:24 ` Casey Schaufler
2019-02-08 10:52 ` Tetsuo Handa
2019-02-08 16:23 ` Casey Schaufler
2019-02-09 0:28 ` Tetsuo Handa
2019-02-09 1:40 ` Tetsuo Handa
2019-02-08 21:49 ` Kees Cook
2019-02-08 21:33 ` Kees Cook
2018-08-30 3:43 ` WARNING in apparmor_secid_to_secctx syzbot
2018-09-01 9:18 ` John Johansen
2018-09-02 4:33 ` Dmitry Vyukov
2018-09-02 4:52 ` John Johansen
2018-09-02 5:03 ` Dmitry Vyukov
2018-09-02 5:03 ` syzbot
2018-09-02 5:05 ` Dmitry Vyukov
2018-09-02 5:46 ` syzbot
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