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Date: Wed, 29 Sep 2021 13:06:59 -0700
From: Kees Cook <keescook@...omium.org>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Alexander Popov <alex.popov@...ux.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>,
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Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
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Andy Lutomirski <luto@...nel.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
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Will Deacon <will.deacon@....com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Laura Abbott <labbott@...hat.com>,
David S Miller <davem@...emloft.net>,
Borislav Petkov <bp@...en8.de>, kernel-hardening@...ts.openwall.com,
linux-hardening@...r.kernel.org, linux-doc@...r.kernel.org,
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Subject: Re: [PATCH] Introduce the pkill_on_warn boot parameter
On Wed, Sep 29, 2021 at 12:03:36PM -0700, Dave Hansen wrote:
> 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;
I like this idea. I can't tell if Linus would tolerate it, though. But I
really have wanted a middle ground like BUG(). Having only WARN() and
panic() is not very friendly. :(
> > 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.
Right, this needs to be moved into the callers of __warn() (i.e.
report_bug(), and warn_slowpath_fmt()), likely with some small
refactoring in report_bug().
--
Kees Cook
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