From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751665AbbINSuI (ORCPT ); Mon, 14 Sep 2015 14:50:08 -0400 Received: from mail2-relais-roc.national.inria.fr ([192.134.164.83]:4549 "EHLO mail2-relais-roc.national.inria.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751017AbbINSuG (ORCPT ); Mon, 14 Sep 2015 14:50:06 -0400 X-IronPort-AV: E=Sophos;i="5.17,530,1437429600"; d="scan'208";a="177492944" Date: Mon, 14 Sep 2015 20:50:03 +0200 (CEST) From: Julia Lawall X-X-Sender: jll@localhost6.localdomain6 To: Mikulas Patocka cc: Mike Snitzer , device-mapper development , Alasdair Kergon , kernel-janitors@vger.kernel.org, Neil Brown , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, sergey.senozhatsky@gmail.com Subject: Re: [PATCH 12/39] dm: drop null test before destroy functions In-Reply-To: Message-ID: References: <1442146532-9100-1-git-send-email-Julia.Lawall@lip6.fr> <1442146532-9100-13-git-send-email-Julia.Lawall@lip6.fr> <20150914140040.GA11815@redhat.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 Mon, 14 Sep 2015, Mikulas Patocka wrote: > > > On Mon, 14 Sep 2015, Mike Snitzer wrote: > > > On Mon, Sep 14 2015 at 9:46am -0400, > > Mikulas Patocka wrote: > > > > > > > > > > > On Sun, 13 Sep 2015, Julia Lawall wrote: > > > > > > > Remove unneeded NULL test. > > > > > > > > The semantic patch that makes this change is as follows: > > > > (http://coccinelle.lip6.fr/) > > > > > > > > // > > > > @@ expression x; @@ > > > > -if (x != NULL) > > > > \(kmem_cache_destroy\|mempool_destroy\|dma_pool_destroy\)(x); > > > > // > > > > > > > > Signed-off-by: Julia Lawall > > > > > > > > --- > > > > drivers/md/dm-bufio.c | 3 +-- > > > > drivers/md/dm-cache-target.c | 3 +-- > > > > drivers/md/dm-crypt.c | 6 ++---- > > > > drivers/md/dm-io.c | 3 +-- > > > > drivers/md/dm-log-userspace-base.c | 3 +-- > > > > drivers/md/dm-region-hash.c | 4 +--- > > > > drivers/md/dm.c | 13 ++++--------- > > > > 7 files changed, 11 insertions(+), 24 deletions(-) > > > > > > > > diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c > > > > index 83cc52e..8ad39b6 100644 > > > > --- a/drivers/md/dm-bufio.c > > > > +++ b/drivers/md/dm-bufio.c > > > > @@ -1864,8 +1864,7 @@ static void __exit dm_bufio_exit(void) > > > > for (i = 0; i < ARRAY_SIZE(dm_bufio_caches); i++) { > > > > struct kmem_cache *kc = dm_bufio_caches[i]; > > > > > > > > - if (kc) > > > > - kmem_cache_destroy(kc); > > > > + kmem_cache_destroy(kc); > > > > } > > > > > > The variable here can be NULL. I don't know how did you conclude that it > > > cannot. It seems that you didn't test the patch, if you did, you'd hit > > > NULL pointer dereference here. > > > > kmem_cache_destroy(), mempool_destroy(), etc all check for NULL and just > > return. So there is no need for the callers to check for NULL too. > > > > Mike > > I see. It was recent change that I missed. The relevant commits were in the cover letter: kmem_cache_destroy (commit 3942d29918522) mempool_destroy (commit 4e3ca3e033d1) dma_pool_destroy (commit 44d7175da6ea) julia From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julia Lawall Date: Mon, 14 Sep 2015 18:50:03 +0000 Subject: Re: [PATCH 12/39] dm: drop null test before destroy functions Message-Id: List-Id: References: <1442146532-9100-1-git-send-email-Julia.Lawall@lip6.fr> <1442146532-9100-13-git-send-email-Julia.Lawall@lip6.fr> <20150914140040.GA11815@redhat.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Mikulas Patocka Cc: Mike Snitzer , device-mapper development , Alasdair Kergon , kernel-janitors@vger.kernel.org, Neil Brown , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, sergey.senozhatsky@gmail.com On Mon, 14 Sep 2015, Mikulas Patocka wrote: > > > On Mon, 14 Sep 2015, Mike Snitzer wrote: > > > On Mon, Sep 14 2015 at 9:46am -0400, > > Mikulas Patocka wrote: > > > > > > > > > > > On Sun, 13 Sep 2015, Julia Lawall wrote: > > > > > > > Remove unneeded NULL test. > > > > > > > > The semantic patch that makes this change is as follows: > > > > (http://coccinelle.lip6.fr/) > > > > > > > > // > > > > @@ expression x; @@ > > > > -if (x != NULL) > > > > \(kmem_cache_destroy\|mempool_destroy\|dma_pool_destroy\)(x); > > > > // > > > > > > > > Signed-off-by: Julia Lawall > > > > > > > > --- > > > > drivers/md/dm-bufio.c | 3 +-- > > > > drivers/md/dm-cache-target.c | 3 +-- > > > > drivers/md/dm-crypt.c | 6 ++---- > > > > drivers/md/dm-io.c | 3 +-- > > > > drivers/md/dm-log-userspace-base.c | 3 +-- > > > > drivers/md/dm-region-hash.c | 4 +--- > > > > drivers/md/dm.c | 13 ++++--------- > > > > 7 files changed, 11 insertions(+), 24 deletions(-) > > > > > > > > diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c > > > > index 83cc52e..8ad39b6 100644 > > > > --- a/drivers/md/dm-bufio.c > > > > +++ b/drivers/md/dm-bufio.c > > > > @@ -1864,8 +1864,7 @@ static void __exit dm_bufio_exit(void) > > > > for (i = 0; i < ARRAY_SIZE(dm_bufio_caches); i++) { > > > > struct kmem_cache *kc = dm_bufio_caches[i]; > > > > > > > > - if (kc) > > > > - kmem_cache_destroy(kc); > > > > + kmem_cache_destroy(kc); > > > > } > > > > > > The variable here can be NULL. I don't know how did you conclude that it > > > cannot. It seems that you didn't test the patch, if you did, you'd hit > > > NULL pointer dereference here. > > > > kmem_cache_destroy(), mempool_destroy(), etc all check for NULL and just > > return. So there is no need for the callers to check for NULL too. > > > > Mike > > I see. It was recent change that I missed. The relevant commits were in the cover letter: kmem_cache_destroy (commit 3942d29918522) mempool_destroy (commit 4e3ca3e033d1) dma_pool_destroy (commit 44d7175da6ea) julia