From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932812AbbHZFtF (ORCPT ); Wed, 26 Aug 2015 01:49:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34021 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751951AbbHZFtD (ORCPT ); Wed, 26 Aug 2015 01:49:03 -0400 Message-ID: <55DD5349.6030107@redhat.com> Date: Wed, 26 Aug 2015 13:48:57 +0800 From: Jason Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0 MIME-Version: 1.0 To: Joe Perches CC: gleb@kernel.org, pbonzini@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, cornelia.huck@de.ibm.com, "Michael S. Tsirkin" Subject: Re: [PATCH V2 1/3] kvm: use kmalloc() instead of kzalloc() during iodev register/unregister References: <1440488835-4388-1-git-send-email-jasowang@redhat.com> <1440516546.2670.88.camel@perches.com> <55DD50FA.1050608@redhat.com> <1440567947.2670.179.camel@perches.com> In-Reply-To: <1440567947.2670.179.camel@perches.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/26/2015 01:45 PM, Joe Perches wrote: > On Wed, 2015-08-26 at 13:39 +0800, Jason Wang wrote: >> > >> > On 08/25/2015 11:29 PM, Joe Perches wrote: >>> > > On Tue, 2015-08-25 at 15:47 +0800, Jason Wang wrote: >>>>> > >> > All fields of kvm_io_range were initialized or copied explicitly >>>>> > >> > afterwards. So switch to use kmalloc(). >>> > > Is there any compiler added alignment padding >>> > > in either structure? If so, those padding >>> > > areas would now be uninitialized and may leak >>> > > kernel data if copied to user-space. >>> > > >> > I get your concern, but I don't a way to copy them to userspace, did you? > I didn't look. > > I just wanted you to be aware there's a difference > and a reason why kzalloc might be used even though > all structure members are initialized. > I see, thanks for the reminding. Looks like we are safe and I will add something like "kvm_io_range was never accessed by userspace" in the commit log if there's a new version.