linux-kernel - Re: [PATCH v2 2/4] printk/kdb: Handle more message headers

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Date:   Fri, 11 Nov 2016 19:13:03 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Joe Perches <joe@...ches.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Jason Wessel <jason.wessel@...driver.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, Chris Mason <clm@...com>,
        Josef Bacik <jbacik@...com>, David Sterba <dsterba@...e.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] printk/kdb: Handle more message headers

On Fri 2016-11-11 12:35:13, Steven Rostedt wrote:
> On Wed,  9 Nov 2016 13:41:29 +0100
> Petr Mladek <pmladek@...e.com> wrote:
> 
> > diff --git a/include/linux/printk.h b/include/linux/printk.h
> > index eac1af8502bb..a0859e169bc3 100644
> > --- a/include/linux/printk.h
> > +++ b/include/linux/printk.h
> > @@ -31,6 +31,14 @@ static inline const char *printk_skip_level(const char *buffer)
> >  	return buffer;
> >  }
> >  
> > +static inline const char *printk_skip_headers(const char *buffer)
> > +{
> > +	while (printk_get_level(buffer))
> > +		buffer = printk_skip_level(buffer);
> 
> Hmm, shouldn't there be a length passed in here. What happens if buffer
> ends with a header. Can't this overflow?

It is OK when the string has the trailing '\0'. This is the case here.

Note that printk_skip_level() and printk_get_level() would have the
same problem if only the first byte of the header fit the buffer.

Best Regards,
Petr