From mboxrd@z Thu Jan 1 00:00:00 1970 From: annie li Subject: Re: [Xen-devel][PATCH net-next v2] xen-netfront: clean up code in xennet_release_rx_bufs Date: Thu, 16 Jan 2014 21:42:19 +0800 Message-ID: <52D7E1BB.8000706@oracle.com> References: <1389830228-2381-1-git-send-email-Annie.li@oracle.com> <52D7BE19.2010009@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: xen-devel@lists.xen.org, netdev@vger.kernel.org, davem@davemloft.net, konrad.wilk@oracle.com, ian.campbell@citrix.com, wei.liu2@citrix.com, andrew.bennieston@citrix.com To: David Vrabel Return-path: Received: from userp1040.oracle.com ([156.151.31.81]:40675 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753068AbaAPNme (ORCPT ); Thu, 16 Jan 2014 08:42:34 -0500 In-Reply-To: <52D7BE19.2010009@citrix.com> Sender: netdev-owner@vger.kernel.org List-ID: On 2014-1-16 19:10, David Vrabel wrote: > On 15/01/14 23:57, Annie Li wrote: >> This patch implements two things: >> >> * release grant reference and skb for rx path, this fixex resource leaking. >> * clean up grant transfer code kept from old netfront(2.6.18) which grants >> pages for access/map and transfer. But grant transfer is deprecated in current >> netfront, so remove corresponding release code for transfer. >> >> gnttab_end_foreign_access_ref may fail when the grant entry is currently used >> for reading or writing. But this patch does not cover this and improvement for >> this failure may be implemented in a separate patch. > I don't think replacing a resource leak with a security bug is a good idea. > > If you would prefer not to fix the gnttab_end_foreign_access() call, I > think you can fix this in netfront by taking a reference to the page > before calling gnttab_end_foreign_access(). This will ensure the page > isn't freed until the subsequent kfree_skb(), or the gref is released by > the foreign domain (whichever is later). What I thought is to split the implementation into two patches, this patch fixes the rx path resource leak(just like what tx path does), then a separate patch fixes gnttab_end_foreign_access_ref failure issue for both tx/rx through taking reference to the page before gnttab_end_foreign_access. If you'd like they are posted together, I will create new patch for the latter and then post them.:-) Thanks Annie