Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752625AbbGBOGk (ORCPT ); Thu, 2 Jul 2015 10:06:40 -0400 Received: from out5-smtp.messagingengine.com ([66.111.4.29]:53107 "EHLO out5-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752534AbbGBOGb (ORCPT ); Thu, 2 Jul 2015 10:06:31 -0400 X-Sasl-enc: 9qd7Z3JF0fcx1u+DjcyhJ03/7h4UpDWJ+S//CnO81GQu 1435845990 Date: Thu, 2 Jul 2015 17:06:29 +0300 From: Sergei Zviagintsev To: David Herrmann Cc: Greg Kroah-Hartman , Daniel Mack , David Herrmann , Djalal Harouni , linux-kernel Subject: Re: [PATCH RFC 3/5] kdbus: do explicit overflow check in kdbus_conn_quota_inc() Message-ID: <20150702140629.GT17917@localhost.localdomain> References: <1435497454-10464-1-git-send-email-sergei@s15v.net> <1435497454-10464-4-git-send-email-sergei@s15v.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2211 Lines: 60 Hi, On Thu, Jul 02, 2015 at 10:35:30AM +0200, David Herrmann wrote: > Hi > > On Sun, Jun 28, 2015 at 3:17 PM, Sergei Zviagintsev wrote: > > Replace the use of max() with explicit and obvious overflow check. > > > > Signed-off-by: Sergei Zviagintsev > > --- > > ipc/kdbus/connection.c | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/ipc/kdbus/connection.c b/ipc/kdbus/connection.c > > index af044f93c14f..1d44e280eff0 100644 > > --- a/ipc/kdbus/connection.c > > +++ b/ipc/kdbus/connection.c > > @@ -668,9 +668,11 @@ int kdbus_conn_quota_inc(struct kdbus_conn *c, struct kdbus_user *u, > > > > id = u ? u->id : KDBUS_USER_KERNEL_ID; > > if (id >= c->n_quota) { > > - unsigned int users; > > + unsigned int users = KDBUS_ALIGN8(id) + 8; > > + > > + if (users < id) /* overflow */ > > + users = id; > > > > - users = max(KDBUS_ALIGN8(id) + 8, id); > > To me, the max() looks fine. I mean, it should be obvious that it > checks for an overflow, right? Otherwise, I'd prefer adding a comment > instead of the explicit conditional. Well, at first sight I assumed that there was some clever algorithm which later had been quick-fixed and so on... I am not sure about commenting current variant, as CodingStyle tells us to write obvious code instead of explanations. And if it is already obvious, then it doesn't need a comment, right? :) In another letter of this series I mentioned commits af8e2f750985 and ac5c385cc67a from out-of-tree kdbus repo, which show that not all of these overflow things are obvious for maintainer, not talking about someone who isn't familiar with the code. > > Thanks > David > > > quota = krealloc(c->quota, users * sizeof(*quota), > > GFP_KERNEL | __GFP_ZERO); > > if (!quota) > > -- > > 1.8.3.1 > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/