linux-kernel - Re: [PATCH 2/5] trace-cmd: Fix NULL pointer being passed to memcpy

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Message-ID: <20171009222710.zl5awmvxe6mxzqgk@mikesart-cos>
Date:   Mon, 9 Oct 2017 16:27:10 -0600
From:   Michael Sartain <mikesart@...tmail.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] trace-cmd: Fix NULL pointer being passed to memcpy

On Mon, Oct 09, 2017 at 06:24:32PM -0400, Steven Rostedt wrote:
> On Sat, 12 Aug 2017 11:30:44 -0600
> Michael Sartain <mikesart@...tmail.com> wrote:
> 
> > Signed-off-by: Michael Sartain <mikesart@...tmail.com>
> > ---
> >  trace-output.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/trace-output.c b/trace-output.c
> > index bfe6331..84b21b0 100644
> > --- a/trace-output.c
> > +++ b/trace-output.c
> > @@ -929,7 +929,11 @@ tracecmd_add_option(struct tracecmd_output *handle,
> >  		free(option);
> >  		return NULL;
> >  	}
> > -	memcpy(option->data, data, size);
> > +
> > +	/* Some IDs (like TRACECMD_OPTION_TRACECLOCK) pass NULL data */
> > +	if (data)
> > +		memcpy(option->data, data, size);
> 
> Is this a problem, as when this happens, size should be zero. Does it
> crash with data=NULL and size=0, or have you seen size not be zero?

I got an ASAN warning, but you are correct - the size was 0 and it did
not crash.