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Subject: Re: [PATCH v19 06/25] x86/cet: Add control-protection fault handler
To:     Borislav Petkov <bp@alien8.de>
Cc:     x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Andy Lutomirski <luto@kernel.org>,
        Balbir Singh <bsingharora@gmail.com>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Eugene Syromiatnikov <esyr@redhat.com>,
        Florian Weimer <fweimer@redhat.com>,
        "H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Kees Cook <keescook@chromium.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Nadav Amit <nadav.amit@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
        Peter Zijlstra <peterz@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
        Dave Martin <Dave.Martin@arm.com>,
        Weijiang Yang <weijiang.yang@intel.com>,
        Pengfei Xu <pengfei.xu@intel.com>,
        Michael Kerrisk <mtk.manpages@gmail.com>
References: <20210203225547.32221-1-yu-cheng.yu@intel.com>
 <20210203225547.32221-7-yu-cheng.yu@intel.com>
 <20210205135927.GH17488@zn.tnic>
 <2d829cba-784e-635a-e0c5-a7b334fa9b40@intel.com>
 <20210208182009.GE18227@zn.tnic>
 <690bc3b9-2890-e68d-5e4b-cda5c21b496b@intel.com>
 <20210208185341.GF18227@zn.tnic>
From:   "Yu, Yu-cheng" <yu-cheng.yu@intel.com>
Message-ID: <0e0c9e9d-aee1-ad1e-6c63-21b58a52163f@intel.com>
Date:   Mon, 8 Feb 2021 11:23:18 -0800
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On 2/8/2021 10:53 AM, Borislav Petkov wrote:
> On Mon, Feb 08, 2021 at 10:50:07AM -0800, Yu, Yu-cheng wrote:
>> I have not run into the situation.  Initially it was there because other
>> faults have it.
> 
> Which other faults?

exc_general_protection() and do_trap() both call show_signal(), which 
then calls printk_ratelimit().

> 
>> When you asked, I went through it and put out my reasoning.
> 
> What does that mean?
> 

I went through my patch and check if ratelimit is necessary, and then 
describe the finding.

>> I think it still makes sense to keep it.
> 
> Because you have a hunch or you actually have an objective reason why?
> 

For example, if a shell script, in a loop re-starts an app when it 
exits, and the app is causing control-protection fault.  The log 
messages should be rate limited.