linux-kernel - Re: [PATCH v2 0/2] Introduce the pkill_on

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <16baa1f4-972d-c781-2d57-508296a83bfb@schaufler-ca.com>
Date:   Thu, 18 Nov 2021 10:30:32 -0800
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Alexander Popov <alex.popov@...ux.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Paul McKenney <paulmck@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Joerg Roedel <jroedel@...e.de>,
        Maciej Rozycki <macro@...am.me.uk>,
        Muchun Song <songmuchun@...edance.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Robin Murphy <robin.murphy@....com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Petr Mladek <pmladek@...e.com>,
        Luis Chamberlain <mcgrof@...nel.org>, Wei Liu <wl@....org>,
        John Ogness <john.ogness@...utronix.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Jann Horn <jannh@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Will Deacon <will@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Laura Abbott <labbott@...nel.org>,
        David S Miller <davem@...emloft.net>,
        Borislav Petkov <bp@...en8.de>, Arnd Bergmann <arnd@...db.de>,
        Andrew Scull <ascull@...gle.com>,
        Marc Zyngier <maz@...nel.org>, Jessica Yu <jeyu@...nel.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Wang Qing <wangqing@...o.com>, Mel Gorman <mgorman@...e.de>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Andrew Klychkov <andrew.a.klychkov@...il.com>,
        Mathieu Chouquet-Stringer <me@...hieu.digital>,
        Daniel Borkmann <daniel@...earbox.net>,
        Stephen Kitt <steve@....org>, Stephen Boyd <sboyd@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Mike Rapoport <rppt@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        linux-hardening@...r.kernel.org,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>, notify@...nel.org,
        main@...ts.elisa.tech, safety-architecture@...ts.elisa.tech,
        devel@...ts.elisa.tech, Shuah Khan <shuah@...nel.org>,
        Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH v2 0/2] Introduce the pkill_on_warn parameter

On 11/18/2021 9:32 AM, Kees Cook wrote:
> On Tue, Nov 16, 2021 at 11:00:23AM -0800, Casey Schaufler wrote:
>> On 11/16/2021 10:41 AM, Kees Cook wrote:
>>> On Tue, Nov 16, 2021 at 12:12:16PM +0300, Alexander Popov wrote:
>>>> What if the Linux kernel had a LSM module responsible for error handling policy?
>>>> That would require adding LSM hooks to BUG*(), WARN*(), KERN_EMERG, etc.
>>>> In such LSM policy we can decide immediately how to react on the kernel error.
>>>> We can even decide depending on the subsystem and things like that.
>>> That would solve the "atomicity" issue the WARN tracepoint solution has,
>>> and it would allow for very flexible userspace policy.
>>>
>>> I actually wonder if the existing panic_on_* sites should serve as a
>>> guide for where to put the hooks. The current sysctls could be replaced
>>> by the hooks and a simple LSM.
>> Do you really want to make error handling a "security" issue?
>> If you add security_bug(), security_warn_on() and the like
>> you're begging that they be included in SELinux (AppArmor) policy.
>> BPF, too, come to think of it. Is that what you want?
> Yeah, that is what I was thinking. This would give the LSM a view into
> kernel state, which seems a reasonable thing to do. If system integrity
> is compromised, an LSM may want to stop trusting things.

How are you planning to communicate the security relevance of the
warning to the LSM? I don't think that __FILE__, __LINE__ or __func__
is great information to base security policy on. Nor is a backtrace.

> A dedicated error-handling LSM could be added for those hooks that
> implemented the existing default panic_on_* sysctls, and could expand on
> that logic for other actions.

I can see having an interface like LSM for choosing a bug/warn policy.
I worry about expanding the LSM hook list for a case where I would
hope no existing LSM would use them, and the new LSM doesn't use any
of the existing hooks.