From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from ganesha.gnumonks.org (ganesha.gnumonks.org [213.95.27.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3E9DC18BC1C for ; Fri, 25 Oct 2024 10:26:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.27.120 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729852015; cv=none; b=LOdMDrQ4PhPPbhr1N+5B9yvMPcxUDMwO1ydQRCuo36U7gVu4/Geo5YweIdMPzECl503fUBlQXuOPSikCB1xNUfHTozFq6VxwyDdtH8H47QDwF0iYMpEaWwRl2uF0uwYHgTcSqn84NEUtQIarf/8VzhTi+pWGE8HmQkV/fQvonlM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729852015; c=relaxed/simple; bh=wVrFjVrn/x/atj01oCFmkK9JuMNBrOt9u038a9RovP8=; h=Date:From:To:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GOdDHSw0bpUT2TETezFV2m+MUt1dudh973mUmzEziDfQ0ATa9amLaJLenRI1UetwAFLo5BOXCtLiuTIiYg9LBPAUyug+QsPTUHris2v4L4sMHNBQhirbMQ4yJfEQrbNfnIKoJA4Ik7AzZuI5Wzfzrr7me082d4PEdpKSRoWSuGk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org; spf=pass smtp.mailfrom=gnumonks.org; arc=none smtp.client-ip=213.95.27.120 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gnumonks.org Received: from [78.30.37.63] (port=34136 helo=gnumonks.org) by ganesha.gnumonks.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1t4HWq-007LOV-NP; Fri, 25 Oct 2024 12:26:50 +0200 Date: Fri, 25 Oct 2024 12:26:47 +0200 From: Pablo Neira Ayuso To: Phil Sutter , Florian Westphal , Matthieu Baerts , netfilter-devel@vger.kernel.org, Jozsef Kadlecsik , coreteam@netfilter.org Subject: Re: Netfilter: suspicious RCU usage in __nft_rule_lookup Message-ID: References: <20241024232230.GA23717@breakpoint.cc> <40d071e1-4c13-49c9-8cac-14c1377eaf86@kernel.org> <20241025092356.GA11843@breakpoint.cc> Precedence: bulk X-Mailing-List: netfilter-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Spam-Score: -1.9 (-) On Fri, Oct 25, 2024 at 11:46:33AM +0200, Phil Sutter wrote: > On Fri, Oct 25, 2024 at 11:23:56AM +0200, Florian Westphal wrote: > > Matthieu Baerts wrote: > > > While at it, I had a question related to the rules' list: in > > > __nft_release_basechain() from the same nf_tables_api.c file, list's > > > entries are not removed with the _rcu variant → is it OK to do that > > > because this function is only called last at the cleanup time, when no > > > other readers can iterate over the list? So similar to what is done in > > > __nft_release_table()? > > > > Looks like __nft_release_basechain() is broken from start, I don't see > > how it can work, it doesn't call synchronize_rcu or anything like that > > afaics. > > > > No idea what to do here. > > It will vanish with my name-based netdev hooks series (the second part). > I could prepare a patch for nf/stable which merely kills that function - > dropping netdev-family chains upon removal of last interface is > inconsistent wrt. flowtables which remain in place. I like the idea of keeping the basechain in place. With chain update support, it makes sense to add a basechain then update it with the devices to hook in. But chain device updates are only recently supported: b9703ed44ffbfba85c103b9de01886a225e14b38 Author: Pablo Neira Ayuso Date: Fri Apr 21 00:34:31 2023 +0200 netfilter: nf_tables: support for adding new devices to an existing netdev chain that is, in older kernels, this chain would remain unused because updates are not be possible. > Another alternative might be to call synchronize_rcu() in there, but it > slows down interface teardown AIUI. Else unregister objects from lists under mutex then call_rcu() to release them. Then, take you patch so new kernel don't remove the basechain.