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 638CB1D8E10 for ; Fri, 25 Oct 2024 13:16:31 +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=1729862194; cv=none; b=DbKCbA2gVsbxFci6knmYW3nI/6oWpimZd1qwxdaebTvpLz7sXdwwnanAttFGN7hFbhpqg3zU94HFDlMhgyxlx1lFay83t12EJ0773+Q0eKAK5EkdECRrDIh75Y0qyXwU3mfPJ5y22+v6s3hZ9rHoSRoVWza0TUzOCz5gb0Whe40= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729862194; c=relaxed/simple; bh=tvBpiwHuj3BxZghpbpmhk8E40bUHtp1p5bRZgZawN9g=; h=Date:From:To:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=hlf/QhPW2rCSVVPuSwXD3WuQUu9O97KynER28xfgorrQLTJNjpQBOlbxHAdsvw+O/PCTwuA/p91Q60/HZFOKJDsDDFD5lRsFWFqnvOmwDPd3l59msUpoV41ZFXSH6eGUM50dOW2flKFYtpv2h6ReMNJ+3LyRtv6B8jmTEg7OK8I= 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=36464 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 1t4KB0-007pGn-Uq; Fri, 25 Oct 2024 15:16:29 +0200 Date: Fri, 25 Oct 2024 15:16:26 +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: multipart/mixed; boundary="5bul5KrhXaosgpen" Content-Disposition: inline In-Reply-To: X-Spam-Score: -1.8 (-) --5bul5KrhXaosgpen Content-Type: text/plain; charset=utf-8 Content-Disposition: inline On Fri, Oct 25, 2024 at 01:43:28PM +0200, Pablo Neira Ayuso wrote: > On Fri, Oct 25, 2024 at 12:56:03PM +0200, Phil Sutter wrote: [...] > > We would not change behaviour in stable this way, also not the worst > > thing to do. Your call! > > I am still exploring how ugly this fix looks, you will see get to know. This is a quick preview, compile-tested only at this stage. --5bul5KrhXaosgpen Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="candidate-fix.patch" diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h index 91ae20cb7648..8dd8e278843d 100644 --- a/include/net/netfilter/nf_tables.h +++ b/include/net/netfilter/nf_tables.h @@ -1120,6 +1120,7 @@ struct nft_chain { char *name; u16 udlen; u8 *udata; + struct rcu_head rcu_head; /* Only used during control plane commit phase: */ struct nft_rule_blob *blob_next; @@ -1282,6 +1283,7 @@ struct nft_table { struct list_head sets; struct list_head objects; struct list_head flowtables; + possible_net_t net; u64 hgenerator; u64 handle; u32 use; diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index a24fe62650a7..762879187edb 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -1495,6 +1495,7 @@ static int nf_tables_newtable(struct sk_buff *skb, const struct nfnl_info *info, INIT_LIST_HEAD(&table->sets); INIT_LIST_HEAD(&table->objects); INIT_LIST_HEAD(&table->flowtables); + write_pnet(&table->net, net); table->family = family; table->flags = flags; table->handle = ++nft_net->table_handle; @@ -11430,22 +11431,39 @@ int nft_data_dump(struct sk_buff *skb, int attr, const struct nft_data *data, } EXPORT_SYMBOL_GPL(nft_data_dump); -int __nft_release_basechain(struct nft_ctx *ctx) +static void __nft_release_basechain_rcu(struct rcu_head *head) { + struct nft_chain *chain = container_of(head, struct nft_chain, rcu_head); struct nft_rule *rule, *nr; + struct nft_ctx ctx = { + .family = chain->table->family, + .net = read_pnet(&chain->table->net), + }; + + list_for_each_entry_safe(rule, nr, &chain->rules, list) { + list_del(&rule->list); + nf_tables_rule_release(&ctx, rule); + } + nf_tables_chain_destroy(chain); + put_net(ctx.net); +} + +int __nft_release_basechain(struct nft_ctx *ctx) +{ + struct nft_rule *rule; if (WARN_ON(!nft_is_base_chain(ctx->chain))) return 0; nf_tables_unregister_hook(ctx->net, ctx->chain->table, ctx->chain); - list_for_each_entry_safe(rule, nr, &ctx->chain->rules, list) { - list_del(&rule->list); + list_for_each_entry(rule, &ctx->chain->rules, list) nft_use_dec(&ctx->chain->use); - nf_tables_rule_release(ctx, rule); - } + nft_chain_del(ctx->chain); nft_use_dec(&ctx->table->use); - nf_tables_chain_destroy(ctx->chain); + get_net(ctx->net); + + call_rcu(&ctx->chain->rcu_head, __nft_release_basechain_rcu); return 0; } --5bul5KrhXaosgpen--