linux-kernel - Re: [PATCH 1/1] drivers/s390/cio/qdio_main.c: replace shift loop by ilog2

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 21 May 2014 14:32:27 +0200 (CEST)
From:	Sebastian Ott <sebott@...ux.vnet.ibm.com>
To:	Joe Perches <joe@...ches.com>,
	Ursula Braun <ursula.braun@...ibm.com>
cc:	Fabian Frederick <fabf@...net.be>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	akpm <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/1] drivers/s390/cio/qdio_main.c: replace shift loop by
 ilog2

On Tue, 20 May 2014, Joe Perches wrote:
> On Tue, 2014-05-20 at 18:37 +0200, Fabian Frederick wrote:
> > This is untested.
> []
> > diff --git a/drivers/s390/cio/qdio_main.c b/drivers/s390/cio/qdio_main.c
> []
> > @@ -411,15 +411,14 @@ static inline void qdio_stop_polling(struct qdio_q *q)
> >  
> >  static inline void account_sbals(struct qdio_q *q, int count)
> >  {
> > -	int pos = 0;
> > +	int pos;
> >  
> >  	q->q_stats.nr_sbal_total += count;
> >  	if (count == QDIO_MAX_BUFFERS_MASK) {
> >  		q->q_stats.nr_sbals[7]++;
> >  		return;
> >  	}
> > -	while (count >>= 1)
> > -		pos++;
> > +	pos = ilog2(count);
> 
> What guarantees count > 0 here?

We would already be screwed when called with count < 0. Ursula, do the
callers assure that count is positive?

Regards,
Sebastian
> 
> count may be better unsigned.
> 
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/