From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752672AbbDDQU6 (ORCPT ); Sat, 4 Apr 2015 12:20:58 -0400 Received: from mail2-relais-roc.national.inria.fr ([192.134.164.83]:36669 "EHLO mail2-relais-roc.national.inria.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752322AbbDDQU4 (ORCPT ); Sat, 4 Apr 2015 12:20:56 -0400 X-IronPort-AV: E=Sophos;i="5.11,522,1422918000"; d="scan'208";a="131616756" Date: Sat, 4 Apr 2015 18:20:53 +0200 (CEST) From: Julia Lawall X-X-Sender: jll@localhost6.localdomain6 To: Greg Kroah-Hartman cc: kernel-janitors@vger.kernel.org, devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] staging: emxx_udc: test returned value In-Reply-To: <20150404160712.GA19278@kroah.com> Message-ID: References: <1428159570-19467-1-git-send-email-Julia.Lawall@lip6.fr> <1428159570-19467-3-git-send-email-Julia.Lawall@lip6.fr> <20150404160712.GA19278@kroah.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 4 Apr 2015, Greg Kroah-Hartman wrote: > On Sat, Apr 04, 2015 at 04:59:30PM +0200, Julia Lawall wrote: > > Put NULL test on the result of the previous call instead on one of its > > arguments. A simplified version of the semantic match that finds this > > problem is as follows (http://coccinelle.lip6.fr/): > > > > // > > r@ > > expression *e1; > > expression *e2; > > identifier f; > > statement S1,S2; > > @@ > > > > e1 = f(...,e2,...); > > ( > > if (e1 == NULL || ...) S1 else S2 > > | > > *if (e2 == NULL || ...) S1 else S2 > > ) > > // > > > > Signed-off-by: Julia Lawall > > > > --- > > drivers/staging/emxx_udc/emxx_udc.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/staging/emxx_udc/emxx_udc.c b/drivers/staging/emxx_udc/emxx_udc.c > > index fbf82bc..7de1e9e 100644 > > --- a/drivers/staging/emxx_udc/emxx_udc.c > > +++ b/drivers/staging/emxx_udc/emxx_udc.c > > @@ -2998,7 +2998,7 @@ static void nbu2ss_ep_fifo_flush(struct usb_ep *_ep) > > } > > > > ep = container_of(_ep, struct nbu2ss_ep, ep); > > - if (!_ep) { > > + if (!ep) { > > This is actually even worse, container_of() can't return NULL. Or if it > does, something is really wrong (it can only happen if the field happens > to be the first field in the structure and the original pointer was > NULL). So I would say that all tests for container_of (and > functions/macros that are just wrappers around container_of()) can just > be deleted as they will never be triggered. Couldn't one say: x = NULL; y = &x->whatever; z = container_of(y, struct blah, whatever); and end up with z being NULL? > Not to say that this patch is wrong at all, I'll go apply it, and you > should add it to the lists of tests in the kernel source, but you should > also consider making a test to catch container_of() results. > > Hm, now that I know coccinelle, I guess I should be able to do this :) Yes indeed :) julia