linux-kernel - Re: [PATCH v19 06/25] x86/cet: Add control-protection fault handler

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Message-ID: <20210208194854.GI18227@zn.tnic>
Date:   Mon, 8 Feb 2021 20:48:54 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Yu, Yu-cheng" <yu-cheng.yu@...el.com>
Cc:     x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>,
        Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [PATCH v19 06/25] x86/cet: Add control-protection fault handler

On Mon, Feb 08, 2021 at 11:23:18AM -0800, Yu, Yu-cheng wrote:
> exc_general_protection() and do_trap() both call show_signal(), which
> then calls printk_ratelimit().

You could've done some git archeology and could've found

  abd4f7505baf ("x86: i386-show-unhandled-signals-v3")

which explains why that ratelimiting is needed.

> 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.

I think you should be able to get where I'm going with this, by now:
please put a comment over the ratelimiting to explain why it is there,
just like the above commit explains.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette