linux-kernel - RE: [PATCH v1 1/1] s390: Use string_upper() instead of open coded variant

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Date:   Tue, 12 Oct 2021 08:04:58 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Heiko Carstens' <hca@...ux.ibm.com>
CC:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>
Subject: RE: [PATCH v1 1/1] s390: Use string_upper() instead of open coded
 variant

From: Heiko Carstens
> Sent: 11 October 2021 11:10
> 
> On Mon, Oct 11, 2021 at 08:21:15AM +0000, David Laight wrote:
> > ...
> > > > +	 * This snprintf() call does two things:
> > > > +	 * - makes a NUL-terminated copy of the input string
> > > > +	 * - pads it with spaces
> > > > +	 */
> > > > +	snprintf(tmp, sizeof(tmp), "%s        ", name);
> > >
> > > I can't say I like code where I have to count spaces in order to
> > > verify if the code is actually correct.
> >
> > What it wrong with "%-8.8s" ?
> 
> There's nothing wrong with it, except lack of imagination on my side ;)
> Andy, care to to send a separate patch just for extmem.c?

Are any of the snprintf() versions actually correct at all?
The implication of the comment is that the input string might
not be NUL terminated - in which case it shouldn't be passed
to snprintf().
I don't think you can assume that the format processing doesn't
do a strlen() of any %s argument - even if a maximum field
width is given.

	David

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