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Subject: Re: [PATCH] Introduce the pkill_on_warn boot parameter
To:     Alexander Popov <alex.popov@linux.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Paul McKenney <paulmck@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Joerg Roedel <jroedel@suse.de>,
        Maciej Rozycki <macro@orcam.me.uk>,
        Muchun Song <songmuchun@bytedance.com>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Petr Mladek <pmladek@suse.com>,
        Kees Cook <keescook@chromium.org>,
        Luis Chamberlain <mcgrof@kernel.org>, Wei Liu <wl@xen.org>,
        John Ogness <john.ogness@linutronix.de>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Alexey Kardashevskiy <aik@ozlabs.ru>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Jann Horn <jannh@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Garnier <thgarnie@google.com>,
        Will Deacon <will.deacon@arm.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Laura Abbott <labbott@redhat.com>,
        David S Miller <davem@davemloft.net>,
        Borislav Petkov <bp@alien8.de>,
        kernel-hardening@lists.openwall.com,
        linux-hardening@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     notify@kernel.org
References: <20210929185823.499268-1-alex.popov@linux.com>
From:   Dave Hansen <dave.hansen@intel.com>
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Message-ID: <323d0784-249d-7fef-6c60-e8426d35b083@intel.com>
Date:   Wed, 29 Sep 2021 12:03:36 -0700
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On 9/29/21 11:58 AM, Alexander Popov wrote:
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -53,6 +53,7 @@ static int pause_on_oops_flag;
>  static DEFINE_SPINLOCK(pause_on_oops_lock);
>  bool crash_kexec_post_notifiers;
>  int panic_on_warn __read_mostly;
> +int pkill_on_warn __read_mostly;
>  unsigned long panic_on_taint;
>  bool panic_on_taint_nousertaint = false;
>  
> @@ -610,6 +611,9 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
>  
>  	print_oops_end_marker();
>  
> +	if (pkill_on_warn && system_state >= SYSTEM_RUNNING)
> +		do_group_exit(SIGKILL);
> +
>  	/* Just a warning, don't kill lockdep. */
>  	add_taint(taint, LOCKDEP_STILL_OK);
>  }

Doesn't this tie into the warning *printing* code?  That's better than
nothing, for sure.  But, if we're doing this for hardening, I think we
would want to kill anyone provoking a warning, not just the first one
that triggered *printing* the warning.