Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932634AbbFJCEZ (ORCPT ); Tue, 9 Jun 2015 22:04:25 -0400 Received: from mail-pa0-f46.google.com ([209.85.220.46]:35205 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751748AbbFJCES (ORCPT ); Tue, 9 Jun 2015 22:04:18 -0400 Date: Wed, 10 Jun 2015 11:04:44 +0900 From: Sergey Senozhatsky To: Christoph Lameter Cc: Andrew Morton , Sergey Senozhatsky , Minchan Kim , Pekka Enberg , Joonsoo Kim , Michal Hocko , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, sergey.senozhatsky.work@gmail.com, Joe Perches Subject: Re: [RFC][PATCH 0/5] do not dereference NULL pools in pools' destroy() functions Message-ID: <20150610020444.GA566@swordfish> References: <1433851493-23685-1-git-send-email-sergey.senozhatsky@gmail.com> <20150609142523.b717dba6033ee08de997c8be@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23+89 (0255b37be491) (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1544 Lines: 43 On (06/09/15 20:11), Christoph Lameter wrote: > On Tue, 9 Jun 2015, Andrew Morton wrote: > > > Well I like it, even though it's going to cause a zillion little cleanup > > patches. > > > > checkpatch already has a "kfree(NULL) is safe and this check is > > probably not required" test so I guess Joe will need to get busy ;) > > > > I'll park these patches until after 4.1 is released - it's getting to > > that time... > > Why do this at all? this makes things less fragile. > I understand that kfree/kmem_cache_free can take a > null pointer but this is the destruction of a cache and it usually > requires multiple actions to clean things up and these actions have to be > properly sequenced. All other processors have to stop referencing this > cache before it can be destroyed. >I think failing well, it's not just `failing', it's a NULL pointer deref. > if someone does something strange like doing cache destruction with a > NULL pointer is valuable. > a missing check is not `something strange'. it's just happening. (a very quick google search) http://help.lockergnome.com/linux/PATCH-dlm-NULL-dereference-failure-kmem_cache_create--ftopict555436.html http://linux-kernel.2935.n7.nabble.com/PATCH-2-6-30-rc6-Remove-kmem-cache-destroy-in-s3c24xx-dma-init-td460417.html etc. -ss -- 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/