Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751988Ab1DKN3x (ORCPT ); Mon, 11 Apr 2011 09:29:53 -0400 Received: from mx2.parallels.com ([64.131.90.16]:39773 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751007Ab1DKN3w (ORCPT ); Mon, 11 Apr 2011 09:29:52 -0400 Message-ID: <4DA30222.5040902@parallels.com> Date: Mon, 11 Apr 2011 08:29:06 -0500 From: Rob Landley User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.14) Gecko/20110223 Thunderbird/3.1.8 MIME-Version: 1.0 To: "Serge E. Hallyn" CC: , , , Trond Myklebust , Tim Spriggs , Kir Kolyshkin , Pavel Emelyanov Subject: Re: [PATCH 3/3] Compare namespaces when comparing addresses in auth_unix cache. References: <4D9431B3.2070305@parallels.com> <20110405034641.GC6764@hallyn.com> <4D9F24F2.9020603@parallels.com> In-Reply-To: <4D9F24F2.9020603@parallels.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [208.54.86.200] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1608 Lines: 35 On 04/08/2011 10:08 AM, Rob Landley wrote: > On 04/04/2011 10:46 PM, Serge E. Hallyn wrote: >> Does this need to take a reference? Or is there no way for an >> entry to outlive its netns? It sort of looks like >> svcauth_unix_info_release will ensure that doesn't happen, but >> I'm not convinced because other parts of the kernel can get >> to ip_map_init through the struct cache_detail. > > When I wrote this I thought the transport's get_net() and put_net() > would pin it, but after re-reading, the sunrpc code is disgustingly > convoluted enough that I can't easily reconstruct my earlier reasoning. > I'll add a get_net() and put_net() just to not have to worry about it. Ah-ha! Stanislav Kinsbursky helped me reconstruct some of the reasoning: we don't need to take a reference because we never actually dereference the struct net *, all we do is feed them to net_eq() which just compares the pointers for equality. (The inline function exists so it can compile to a constant "return 1" when configured out.) So if the network context did go away (which still shouldn't happen between the rpc_xprt and the struct nfs_client having references to it) we still wouldn't have a use-after-free problem because we're not looking at the memory, just the pointer. So I shouldn't need to add get_net() and put_net() to the cache. Sound about right? Rob -- 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/