From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phil Sutter Subject: Re: [nft PATCH] libnftables: Fix for multiple context instances Date: Mon, 20 Nov 2017 13:54:18 +0100 Message-ID: <20171120125418.GU32305@orbyte.nwl.cc> References: <20171116191024.18908-1-phil@nwl.cc> <20171120123726.GA17459@salvia> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netfilter-devel@vger.kernel.org To: Pablo Neira Ayuso Return-path: Received: from orbyte.nwl.cc ([151.80.46.58]:42396 "EHLO orbyte.nwl.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751073AbdKTMyT (ORCPT ); Mon, 20 Nov 2017 07:54:19 -0500 Content-Disposition: inline In-Reply-To: <20171120123726.GA17459@salvia> Sender: netfilter-devel-owner@vger.kernel.org List-ID: On Mon, Nov 20, 2017 at 01:37:26PM +0100, Pablo Neira Ayuso wrote: > On Thu, Nov 16, 2017 at 08:10:24PM +0100, Phil Sutter wrote: > > If a second context is created, the second call to nft_ctx_free() leads > > to freeing invalid pointers in nft_exit(). Fix this by introducing a > > reference counter so that neither nft_init() nor nft_exit() run more > > than once in a row. > > > > This reference counter has to be protected from parallel access. Do this > > using a mutex in a way that once nft_init() returns, the first call to > > that function running in parallel is guaranteed to be finished - > > otherwise it could happen that things being initialized in one thread > > are already accessed in another one. > > I would prefer this table is placed into the context object, so they > are not global anymore. So I would prefer we fix this the right way(tm). > > Let me know your thoughts, thanks! I don't think that's feasible: Looking at 'mark_tbl' for instance, this is accessed from callbacks in 'mark_type', so we would have to make nft_ctx accessible by all functions dealing with datatypes. Cheers, Phil