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References: <20191216095955.9886-1-penguin-kernel@I-love.SAKURA.ne.jp> <20191217051234.GA54407@google.com>
In-Reply-To: <20191217051234.GA54407@google.com>
From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Tue, 17 Dec 2019 08:54:34 +0100
Message-ID: <CACT4Y+ZV_syKQt6hDwf3WH5-LpFo==rsVsQY7+YCMfpUCtzj_A@mail.gmail.com>
Subject: Re: [PATCH] kconfig: Add kernel config option for fuzz testing.
To:     Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc:     Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Petr Mladek <pmladek@suse.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jslaby@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Tue, Dec 17, 2019 at 6:12 AM Sergey Senozhatsky
<sergey.senozhatsky.work@gmail.com> wrote:
>
> On (19/12/16 18:59), Tetsuo Handa wrote:
> [..]
> > +++ b/kernel/printk/printk.c
> > @@ -1198,6 +1198,14 @@ MODULE_PARM_DESC(ignore_loglevel,
> >
> >  static bool suppress_message_printing(int level)
> >  {
> > +#ifdef CONFIG_KERNEL_BUILT_FOR_FUZZ_TESTING
> > +     /*
> > +      * Changing console_loglevel causes "no output". But ignoring
> > +      * console_loglevel is easier than preventing change of
> > +      * console_loglevel.
> > +      */
> > +     return (level >= CONSOLE_LOGLEVEL_DEFAULT && !ignore_loglevel);
> > +#endif
> >       return (level >= console_loglevel && !ignore_loglevel);
> >  }
>
> Can you fuzz test with `ignore_loglevel'?

We can set ignore_loglevel in syzbot configs, but won't it then print
everything including verbose debug output?