From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.netfilter.org (mail.netfilter.org [217.70.190.124]) (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 55DA82F7F0F; Sun, 18 Oct 2026 00:56:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.190.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792285012; cv=none; b=OcrgrGy8forRbrlU6pKzxtpFcNiYjZGVRRG9EBeYKLCYRLZocO9gBNXyG86EsGRl4U2Td2nW5T4r3HFaCYdiMau2HWtGD1UgZmczm8MLDCbs0RO+3EsC25JPkaoLq/xQEcmLcB98bQRhVuWoGwG9wLVJNhWsZQrsxxqhGWrNnOU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792285012; c=relaxed/simple; bh=RaHOoftn4uL54J6lM1QLM5AKLVbWo8sRMqmdFNql+vc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WTDx4O5Jddy8C08K9/QDgEPr/4kr6zPvFuszHqSVQIu18xUbyQKt8LbJqUWoa0mfZ4uBN0Q9+rVXCQufb4dgPRdWglnvXjzUMHKAnqRTvMYq/ciJcqB2p+a5RUf7KYBJVibntKwjBZB0qkcpQStrynpzdaicYVtcNCmyiVCUXoI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org; spf=pass smtp.mailfrom=netfilter.org; dkim=pass (2048-bit key) header.d=netfilter.org header.i=@netfilter.org header.b=ZN7jboDK; arc=none smtp.client-ip=217.70.190.124 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=netfilter.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=netfilter.org header.i=@netfilter.org header.b="ZN7jboDK" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netfilter.org; s=2025; t=1792285008; bh=nY8Ge8LIbgZMa5CP4CSN2FfE9o/M8QmNqof3KDHOj+k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZN7jboDK93CwGwajaoYV/Wxxbg7ES6UZSe094PutwqqyoJcZVeB7LUkYoUPfYGIPB TF0Oi+2331WMP6OdLPxLiXysBEhp6RpdVuaUQaj1EpetyoDV9S7AnSAI5pg4+nTGo2 a3RlPWBBan3K25/4CU2DqsW1Atn797eIG5W3EDAuiZrxmNz9gGok8xHDYuX27gyoSd eYuKCjNc4SjesFQzQ6XOnVIvRQjmWFTkHwHD10YqlIjBbe7ZRhfXmg6wmmB1+Je8BW CYhPI7n7Cx9vGFTRrFZpp9oFa4ouvUTaJAwwBOVvT9HZcfZ14b9eQfPSxUWk9Mnk7t gDfMjEojnVrjQ== Received: from localhost.localdomain (mail-agni [217.70.190.124]) by mail.netfilter.org (Postfix) with ESMTPSA id AD80F6005F; Sun, 18 Oct 2026 02:56:47 +0200 (CEST) From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org, pabeni@redhat.com, edumazet@kernel.org, horms@kernel.org, fw@strlen.de, ja@ssi.bg Subject: [PATCH net-next 01/15] netfilter: disable br_netfilter in user namespaces Date: Sun, 18 Oct 2026 02:56:24 +0200 Message-ID: <20261018005638.1776148-2-pablo@netfilter.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261018005638.1776148-1-pablo@netfilter.org> References: <20261018005638.1776148-1-pablo@netfilter.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Florian Westphal br_netfilter has way too many bugs, schedule for removal and disable the feature in user namespaces. In particular, we get more and more gadgets to have bridge ports escape rcu_read_lock() protection, then underlying device gets reconfigured (macvlan or something else), then reinject into network stack causes crash because net_device is assumed to still have bridge rx data associated with it. br_netfilter is an ancient kludge that emulates ip stack from within the bridge and then calls into ipv4/ipv6 netfilter hooks to have bridged frames processed via iptables/ip6tables by setting the 'call-iptables' sysctls to 1. It is NOT related to ebtables or nftables 'bridge' family at all. Note that in addition to call-iptables, sysctls, the bridge also exposes call-iptables per bridge device via netlink and sysfs ('BROPT_NF_CALL_IPTABLES') toggles. Those are still available, the brnet structure is scoped to br_netfilter; exposing it bridge-wide is a big no-no. This relies on brnf_device_event() no longer registering the base br_netfilter hooks, so while BROPT_NF_CALL_IPTABLES can be set, it has no effect because the hooks that evaluate this feature bit are never registered. brnf_init_net can no longer depend on CONFIG_SYSCTL, else such builds never disable support in user namespaces. Cc: Nikolay Aleksandrov Signed-off-by: Florian Westphal Reviewed-by: Nikolay Aleksandrov Signed-off-by: Pablo Neira Ayuso --- Documentation/networking/bridge.rst | 5 +++-- net/bridge/br_netfilter_hooks.c | 33 ++++++++++++++++++++--------- 2 files changed, 26 insertions(+), 12 deletions(-) diff --git a/Documentation/networking/bridge.rst b/Documentation/networking/bridge.rst index c1e6ea52c9e5..dded1a6edd60 100644 --- a/Documentation/networking/bridge.rst +++ b/Documentation/networking/bridge.rst @@ -277,8 +277,9 @@ Netfilter ========= The bridge netfilter module is a legacy feature that allows to filter bridged -packets with iptables and ip6tables. Its use is discouraged. Users should -consider using nftables for packet filtering. +packets with iptables and ip6tables. This feature is scheduled for removal and +not available in user namespaces. Consider using nftables for packet filtering +instead. The older ebtables tool is more feature-limited compared to nftables, but just like nftables it doesn't need this module either to function. diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c index 0a394e5f4391..e15355ff215a 100644 --- a/net/bridge/br_netfilter_hooks.c +++ b/net/bridge/br_netfilter_hooks.c @@ -54,6 +54,7 @@ static unsigned int brnf_net_id __read_mostly; struct brnf_net { bool enabled; + bool in_userns; #ifdef CONFIG_SYSCTL struct ctl_table_header *ctl_hdr; @@ -1100,7 +1101,7 @@ static int brnf_device_event(struct notifier_block *unused, unsigned long event, net = dev_net(dev); brnet = net_generic(net, brnf_net_id); - if (brnet->enabled) + if (brnet->enabled || brnet->in_userns) return NOTIFY_OK; ret = nf_register_net_hooks(net, br_nf_ops, ARRAY_SIZE(br_nf_ops)); @@ -1229,9 +1230,11 @@ static inline void br_netfilter_sysctl_default(struct brnf_net *brnf) brnf->filter_pppoe_tagged = 0; brnf->pass_vlan_indev = 0; } +#endif static int br_netfilter_sysctl_init_net(struct net *net) { +#ifdef CONFIG_SYSCTL struct ctl_table *table = brnf_table; struct brnf_net *brnet; @@ -1259,25 +1262,39 @@ static int br_netfilter_sysctl_init_net(struct net *net) return -ENOMEM; } - +#endif return 0; } static void br_netfilter_sysctl_exit_net(struct net *net, struct brnf_net *brnet) { - const struct ctl_table *table = brnet->ctl_hdr->ctl_table_arg; +#ifdef CONFIG_SYSCTL + struct ctl_table_header *header = brnet->ctl_hdr; + const struct ctl_table *table; - unregister_net_sysctl_table(brnet->ctl_hdr); + if (!header) + return; + + table = header->ctl_table_arg; + unregister_net_sysctl_table(header); if (!net_eq(net, &init_net)) kfree(table); +#endif } static int __net_init brnf_init_net(struct net *net) { + if (net->user_ns != &init_user_ns) { + struct brnf_net *brnet = net_generic(net, brnf_net_id); + + brnet->in_userns = true; + pr_warn_once("br_netfilter no longer supported in user namespaces\n"); + return 0; + } + return br_netfilter_sysctl_init_net(net); } -#endif static void __net_exit brnf_exit_net(struct net *net) { @@ -1289,15 +1306,11 @@ static void __net_exit brnf_exit_net(struct net *net) brnet->enabled = false; } -#ifdef CONFIG_SYSCTL br_netfilter_sysctl_exit_net(net, brnet); -#endif } static struct pernet_operations brnf_net_ops __read_mostly = { -#ifdef CONFIG_SYSCTL .init = brnf_init_net, -#endif .exit = brnf_exit_net, .id = &brnf_net_id, .size = sizeof(struct brnf_net), @@ -1318,7 +1331,7 @@ static int __init br_netfilter_init(void) } RCU_INIT_POINTER(nf_br_ops, &br_ops); - printk(KERN_NOTICE "Bridge firewalling registered\n"); + pr_warn("br_netfilter is slated for removal in 2027.\n"); return 0; } -- 2.47.3