From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f172.google.com (mail-pd0-f172.google.com [209.85.192.172]) by kanga.kvack.org (Postfix) with ESMTP id 135646B0035 for ; Wed, 30 Apr 2014 17:19:27 -0400 (EDT) Received: by mail-pd0-f172.google.com with SMTP id g10so2296224pdj.3 for ; Wed, 30 Apr 2014 14:19:26 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTP id td10si18283517pac.304.2014.04.30.14.19.25 for ; Wed, 30 Apr 2014 14:19:25 -0700 (PDT) Date: Wed, 30 Apr 2014 14:19:24 -0700 From: Andrew Morton Subject: Re: [PATCH] dmapool: remove redundant NULL check for dev in dma_pool_create() Message-Id: <20140430141924.8d84f7fdcac3ac3996802aa9@linux-foundation.org> In-Reply-To: <20140429025310.GA5913@devel> References: <20140429025310.GA5913@devel> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Daeseok Youn Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org On Tue, 29 Apr 2014 11:53:10 +0900 Daeseok Youn wrote: > "dev" cannot be NULL because it is already checked before > calling dma_pool_create(). > > Signed-off-by: Daeseok Youn > --- > If dev can be NULL, it has NULL deferencing when kmalloc_node() > is called after enabling CONFIG_NUMA. hm, this is unclear. The code which handles the dev==NULL case was obviously put there deliberately, presumably with the intention of permitting drivers to call dma_pool_create() without a device*. This code is very old. A lot of drivers call dma_pool_create() (I doubt if you audited all of them!) and perhaps there are some which use this feature and have never been run on NUMA hardware. I think I'll apply the patch anyway because such drivers (if they exist) probably need some attending to. I rewrote the changelog thusly: : "dev" cannot be NULL because it is already checked before calling : dma_pool_create(). : : If dev ever was NULL, the code would oops in dev_to_node() after enabling : CONFIG_NUMA. : : It is possible that some driver is using dev==NULL and has never been run : on a NUMA machine. Such a driver is probably outdated, possibly buggy and : will need some attention if it starts triggering NULL derefs. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org