linux-kernel - Re: [PATCH] scripts: recordmcount: fix incorrect use of sprintf

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Message-ID: <20160106112854.GA20574@wfg-t540p.sh.intel.com>
Date:	Wed, 6 Jan 2016 19:28:54 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Colin King <colin.king@...onical.com>,
	Li Bin <huawei.libin@...wei.com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Will Deacon <will.deacon@....com>,
	linux-kernel@...r.kernel.org, Kees Cook <keescook@...gle.com>
Subject: Re: [PATCH] scripts: recordmcount: fix incorrect use of sprintf

Hi Steven,

On Mon, Jan 04, 2016 at 10:42:46AM -0500, Steven Rostedt wrote:
> On Wed, 30 Dec 2015 23:06:41 +0000
> Colin King <colin.king@...onical.com> wrote:
> 
> > From: Colin Ian King <colin.king@...onical.com>
> > 
> > Fix build warning:
> > 
> > scripts/recordmcount.c:589:4: warning: format not a string
> > literal and no format arguments [-Wformat-security]
> >     sprintf("%s: failed\n", file);
> > 
> > Fixes: a50bd43935586 ("ftrace/scripts: Have recordmcount copy the object file")
> > Signed-off-by: Colin Ian King <colin.king@...onical.com>
> > ---
> >  scripts/recordmcount.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
> > index 301d70b..e1675927 100644
> > --- a/scripts/recordmcount.c
> > +++ b/scripts/recordmcount.c
> > @@ -586,7 +586,7 @@ main(int argc, char *argv[])
> >  			do_file(file);
> >  			break;
> >  		case SJ_FAIL:    /* error in do_file or below */
> > -			sprintf("%s: failed\n", file);
> > +			fprintf(stderr, "%s: failed\n", file);
> 
> Paper bag bug. I'm not sure how this passed my tests? My tests check
> for warnings. And I even got a "BUILD SUCCESS" from Fengguang Wu's
> kbuild test robot.

Because the error will only show up on "gcc -Wformat-security".

It tend to raise false positives, so Kees setup a dedicated tree
which enables -Wformat-security as well as quieting the common false
positives. In that way Kees can catch such problems from time to time,
however the limitation is, only upstreamed code can be tested in Kees'
tree.

> I'll apply it, test it, and push it out soon.

Thanks,
Fengguang
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