linux-kernel - Re: [PATCH v2] Add kernel config option for fuzz testing.

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Date:   Fri, 13 Mar 2020 09:31:07 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Jiri Slaby <jslaby@...e.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Garrett <mjg59@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        "Theodore Y . Ts'o" <tytso@....edu>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] Add kernel config option for fuzz testing.

On Thu, Mar 12, 2020 at 06:29:35PM -0400, Steven Rostedt wrote:
> > @@ -705,10 +706,12 @@ static void lockdep_print_held_locks(struct task_struct *p)
> >  	 * It's not reliable to print a task's held locks if it's not sleeping
> >  	 * and it's not the current task.
> >  	 */
> > -	if (p->state == TASK_RUNNING && p != current)
> > -		return;
> > +	unreliable = p->state == TASK_RUNNING && p != current;
> >  	for (i = 0; i < depth; i++) {
> > -		printk(" #%d: ", i);
> > +		if (unreliable)
> > +			printk(" #%d?: ", i);
> > +		else
> > +			printk(" #%d: ", i);
> 
> Have you tried submitting this? Has Peter nacked it?

It has definite UaF potential... do we have a boot parameter that
signals the willingness to trade safetly for more debug output?

Over all, the risk of this going *bang* is quite low I think.