Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) client-ip=23.128.96.37;
Message-ID: <eb41ec87-8e46-4880-9d94-d86849ddadd2@linux.microsoft.com>
Date:   Fri, 8 Dec 2023 12:41:31 -0600
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [RFC PATCH v2 17/19] heki: x86: Update permissions counters
 during text patching
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     =?UTF-8?Q?Micka=C3=ABl_Sala=C3=BCn?= <mic@digikod.net>,
        Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H . Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Kees Cook <keescook@chromium.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Alexander Graf <graf@amazon.com>,
        Chao Peng <chao.p.peng@linux.intel.com>,
        "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
        Forrest Yuan Yu <yuanyu@google.com>,
        James Gowans <jgowans@amazon.com>,
        James Morris <jamorris@linux.microsoft.com>,
        John Andersen <john.s.andersen@intel.com>,
        Marian Rotariu <marian.c.rotariu@gmail.com>,
        =?UTF-8?Q?Mihai_Don=C8=9Bu?= <mdontu@bitdefender.com>,
        =?UTF-8?B?TmljdciZb3IgQ8OuyJt1?= <nicu.citu@icloud.com>,
        Thara Gopinath <tgopinath@microsoft.com>,
        Trilok Soni <quic_tsoni@quicinc.com>,
        Wei Liu <wei.liu@kernel.org>, Will Deacon <will@kernel.org>,
        Yu Zhang <yu.c.zhang@linux.intel.com>,
        Zahra Tarkhani <ztarkhani@microsoft.com>,
        =?UTF-8?Q?=C8=98tefan_=C8=98icleru?= <ssicleru@bitdefender.com>,
        dev@lists.cloudhypervisor.org, kvm@vger.kernel.org,
        linux-hardening@vger.kernel.org, linux-hyperv@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        linux-security-module@vger.kernel.org, qemu-devel@nongnu.org,
        virtualization@lists.linux-foundation.org, x86@kernel.org,
        xen-devel@lists.xenproject.org
References: <20231113022326.24388-1-mic@digikod.net>
 <20231113022326.24388-18-mic@digikod.net>
 <20231113081929.GA16138@noisy.programming.kicks-ass.net>
 <a52d8885-43cc-4a4e-bb47-9a800070779e@linux.microsoft.com>
 <20231127200841.GZ3818@noisy.programming.kicks-ass.net>
 <ea63ae4e-e8ea-4fbf-9383-499e14de2f5e@linux.microsoft.com>
 <20231130113315.GE20191@noisy.programming.kicks-ass.net>
 <624a310b-c0d2-406c-a4a7-d851b3cc68f5@linux.microsoft.com>
 <20231206185134.GA9899@noisy.programming.kicks-ass.net>
Content-Language: en-US
From:   "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
In-Reply-To: <20231206185134.GA9899@noisy.programming.kicks-ass.net>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk


On 12/6/23 12:51, Peter Zijlstra wrote:
> On Wed, Dec 06, 2023 at 10:37:33AM -0600, Madhavan T. Venkataraman wrote:
>>
>>
>> On 11/30/23 05:33, Peter Zijlstra wrote:
>>> On Wed, Nov 29, 2023 at 03:07:15PM -0600, Madhavan T. Venkataraman wrote:
>>>
>>>> Kernel Lockdown
>>>> ---------------
>>>>
>>>> But, we must provide at least some security in V2. Otherwise, it is useless.
>>>>
>>>> So, we have implemented what we call a kernel lockdown. At the end of kernel
>>>> boot, Heki establishes permissions in the extended page table as mentioned
>>>> before. Also, it adds an immutable attribute for kernel text and kernel RO data.
>>>> Beyond that point, guest requests that attempt to modify permissions on any of
>>>> the immutable pages will be denied.
>>>>
>>>> This means that features like FTrace and KProbes will not work on kernel text
>>>> in V2. This is a temporary limitation. Once authentication is in place, the
>>>> limitation will go away.
>>>
>>> So either you're saying your patch 17 / text_poke is broken (so why
>>> include it ?!?) or your statement above is incorrect. Pick one.
>>>
>>
>> It has been included so that people can be aware of the changes.
>>
>> I will remove the text_poke() changes from the patchset and send it later when
>> I have some authentication in place. It will make sense then.
> 
> If you know its broken then fucking say so in the Changelog instead of
> wasting everybody's time.. OMG.

It is not broken. It addresses one part of the problem. The other part is WIP.

I am preparing a detailed response to your comments. I ask you to be patient until then. In fact, I would appreciate your input/suggestions on some problems we are trying to solve in this context. I will mention them in my response.

Madhavan