{"id":2228968,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2228968/?format=json","web_url":"http://patchwork.ozlabs.org/project/netfilter-devel/patch/20260427150500.13754-3-pablo@netfilter.org/","project":{"id":26,"url":"http://patchwork.ozlabs.org/api/1.1/projects/26/?format=json","name":"Netfilter Development","link_name":"netfilter-devel","list_id":"netfilter-devel.vger.kernel.org","list_email":"netfilter-devel@vger.kernel.org","web_url":null,"scm_url":null,"webscm_url":null},"msgid":"<20260427150500.13754-3-pablo@netfilter.org>","date":"2026-04-27T15:05:00","name":"[nf,v6,3/3] netfilter: nft_fwd_netdev: use recursion counter in neigh egress path","commit_ref":null,"pull_url":null,"state":"changes-requested","archived":false,"hash":"5c29cf05d9ff9405b78602d424e6990de6fd8bde","submitter":{"id":1315,"url":"http://patchwork.ozlabs.org/api/1.1/people/1315/?format=json","name":"Pablo Neira Ayuso","email":"pablo@netfilter.org"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/netfilter-devel/patch/20260427150500.13754-3-pablo@netfilter.org/mbox/","series":[{"id":501670,"url":"http://patchwork.ozlabs.org/api/1.1/series/501670/?format=json","web_url":"http://patchwork.ozlabs.org/project/netfilter-devel/list/?series=501670","date":"2026-04-27T15:04:58","name":"[nf,v6,1/3] netfilter: nft_fwd_netdev: add device and headroom validate with neigh forwarding","version":6,"mbox":"http://patchwork.ozlabs.org/series/501670/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2228968/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2228968/checks/","tags":{},"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","netfilter-devel@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=netfilter.org header.i=@netfilter.org\n header.a=rsa-sha256 header.s=2025 header.b=VteptDJU;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=172.234.253.10; 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Mon, 27 Apr 2026 15:05:07 +0000 (UTC)","from localhost.localdomain (mail-agni [217.70.190.124])\n\tby mail.netfilter.org (Postfix) with ESMTPSA id 65C2F60255\n\tfor ; Mon, 27 Apr 2026 17:05:05 +0200 (CEST)"],"ARC-Seal":"i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116;\n\tt=1777302308; cv=none;\n b=OL0urcmL0MYy/XnAwDY3hGY1jM4l5y4RaAxrNQXmrzQTPDK6BGvLdW4thgy+jFgLlUewSRSaopYbcv44osDqSxVserav6CYUJYH0nI4PCOCGpauMmCWLHf/MprONF59hfLBc9HBYd0cC++v0jybvUXudtr8NVBuY8Tl+PfhGqNE=","ARC-Message-Signature":"i=1; a=rsa-sha256; d=subspace.kernel.org;\n\ts=arc-20240116; t=1777302308; c=relaxed/simple;\n\tbh=WYf8vmUKZCf9LfliQ48s5rAtFUvMEeuxXsDMeinDapY=;\n\th=From:To:Subject:Date:Message-ID:In-Reply-To:References:\n\t MIME-Version;\n b=Age7sF9XGVcA5Q8gcYQMXymD3SV+U9DLZoe8NQlKt/QmGBcaFnDcx+yqqB1Z9DTP0oPFtIulnD06GDiBWykWs7xKD9N+AyPo7QHsD8NYtwRFIaiUiowncZeX4hBkzXYHJRYpkiKH+rw+MXWrULajSm8+14neakwbEH4ErT+gXc0=","ARC-Authentication-Results":"i=1; smtp.subspace.kernel.org;\n dmarc=none (p=none dis=none) header.from=netfilter.org;\n spf=pass smtp.mailfrom=netfilter.org;\n dkim=pass (2048-bit key) header.d=netfilter.org header.i=@netfilter.org\n header.b=VteptDJU; arc=none smtp.client-ip=217.70.190.124","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed; d=netfilter.org;\n\ts=2025; t=1777302305;\n\tbh=AaQMBA9tZjn2JyJ2rECwzkiQtV3KoAhPk/5DEMh8n8o=;\n\th=From:To:Subject:Date:In-Reply-To:References:From;\n\tb=VteptDJUhB7LzjHvubc2sxrItesoGW23Ygf97Rf1gxVMM2V/C5rnxy1s/k6urVAnD\n\t pDPoKLcpYu0SKn2gz6DvTqd8FwwM40mkKpsU3DbTQjbZqtQC/MGBUd45K5ax5ye/rw\n\t TOx/ajSeG90xrcmD7n7wL/eCkRmfXx0rftbCPKT6DilEq688J00xy11PWaLOcO3iJC\n\t 2nYpj2isbnE8/oWvs4rwLxkNMlIZOkUIKLWZpGjZNQs9hYgYqTFGLaGy6TIHo1zKoo\n\t QFdvUGdHrV21N4jSOTUka8axj0DYZ4wVMbO/SGaUUclH8UsBgmxxlociIzfrbzOAAe\n\t 1haN3wiztl/Iw==","From":"Pablo Neira Ayuso ","To":"netfilter-devel@vger.kernel.org","Subject":"[PATCH nf,v6 3/3] netfilter: nft_fwd_netdev: use recursion counter in\n neigh egress path","Date":"Mon, 27 Apr 2026 17:05:00 +0200","Message-ID":"<20260427150500.13754-3-pablo@netfilter.org>","X-Mailer":"git-send-email 2.47.3","In-Reply-To":"<20260427150500.13754-1-pablo@netfilter.org>","References":"<20260427150500.13754-1-pablo@netfilter.org>","Precedence":"bulk","X-Mailing-List":"netfilter-devel@vger.kernel.org","List-Id":"","List-Subscribe":"","List-Unsubscribe":"","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit"},"content":"From: Weiming Shi \n\nnft_fwd_neigh can be used in egress chains (NF_NETDEV_EGRESS). When the\nforwarding rule targets the same device or two devices forward to each\nother, neigh_xmit() triggers dev_queue_xmit() which re-enters\nnf_hook_egress(), causing infinite recursion and stack overflow.\n\nMove the nf_get_nf_dup_skb_recursion() accessor and NF_RECURSION_LIMIT\nto the shared header nf_dup_netdev.h as a static inline, so that\nnft_fwd_netdev can use the recursion counter directly without exported\nfunction call overhead. Guard neigh_xmit() with the same recursion\nlimit already used in nf_do_netdev_egress().\n\n[ Updated to cache the nf_get_nf_dup_skb_recursion pointer. --pablo ]\n\nFixes: f87b9464d152 (\"netfilter: nft_fwd_netdev: Support egress hook\")\nReported-by: Xiang Mei \nSigned-off-by: Weiming Shi \nSigned-off-by: Pablo Neira Ayuso \n---\nv6: no changes\n\n include/net/netfilter/nf_dup_netdev.h | 13 +++++++++++++\n net/netfilter/nf_dup_netdev.c | 16 ----------------\n net/netfilter/nft_fwd_netdev.c | 8 ++++++++\n 3 files changed, 21 insertions(+), 16 deletions(-)","diff":"diff --git a/include/net/netfilter/nf_dup_netdev.h b/include/net/netfilter/nf_dup_netdev.h\nindex b175d271aec9..609bcf422a9b 100644\n--- a/include/net/netfilter/nf_dup_netdev.h\n+++ b/include/net/netfilter/nf_dup_netdev.h\n@@ -3,10 +3,23 @@\n #define _NF_DUP_NETDEV_H_\n \n #include \n+#include \n+#include \n \n void nf_dup_netdev_egress(const struct nft_pktinfo *pkt, int oif);\n void nf_fwd_netdev_egress(const struct nft_pktinfo *pkt, int oif);\n \n+#define NF_RECURSION_LIMIT\t2\n+\n+static inline u8 *nf_get_nf_dup_skb_recursion(void)\n+{\n+#ifndef CONFIG_PREEMPT_RT\n+\treturn this_cpu_ptr(&softnet_data.xmit.nf_dup_skb_recursion);\n+#else\n+\treturn ¤t->net_xmit.nf_dup_skb_recursion;\n+#endif\n+}\n+\n struct nft_offload_ctx;\n struct nft_flow_rule;\n \ndiff --git a/net/netfilter/nf_dup_netdev.c b/net/netfilter/nf_dup_netdev.c\nindex e348fb90b8dc..3b0a70e154cd 100644\n--- a/net/netfilter/nf_dup_netdev.c\n+++ b/net/netfilter/nf_dup_netdev.c\n@@ -13,22 +13,6 @@\n #include \n #include \n \n-#define NF_RECURSION_LIMIT\t2\n-\n-#ifndef CONFIG_PREEMPT_RT\n-static u8 *nf_get_nf_dup_skb_recursion(void)\n-{\n-\treturn this_cpu_ptr(&softnet_data.xmit.nf_dup_skb_recursion);\n-}\n-#else\n-\n-static u8 *nf_get_nf_dup_skb_recursion(void)\n-{\n-\treturn ¤t->net_xmit.nf_dup_skb_recursion;\n-}\n-\n-#endif\n-\n static void nf_do_netdev_egress(struct sk_buff *skb, struct net_device *dev,\n \t\t\t\tenum nf_dev_hooks hook)\n {\ndiff --git a/net/netfilter/nft_fwd_netdev.c b/net/netfilter/nft_fwd_netdev.c\nindex c484a757cfb5..65768cbcc211 100644\n--- a/net/netfilter/nft_fwd_netdev.c\n+++ b/net/netfilter/nft_fwd_netdev.c\n@@ -95,6 +95,7 @@ static void nft_fwd_neigh_eval(const struct nft_expr *expr,\n \t\t\t struct nft_regs *regs,\n \t\t\t const struct nft_pktinfo *pkt)\n {\n+\tu8 *nf_dup_skb_recursion = nf_get_nf_dup_skb_recursion();\n \tstruct nft_fwd_neigh *priv = nft_expr_priv(expr);\n \tvoid *addr = ®s->data[priv->sreg_addr];\n \tint oif = regs->data[priv->sreg_dev];\n@@ -153,6 +154,11 @@ static void nft_fwd_neigh_eval(const struct nft_expr *expr,\n \t\tgoto out;\n \t}\n \n+\tif (*nf_dup_skb_recursion > NF_RECURSION_LIMIT) {\n+\t\tverdict = NF_DROP;\n+\t\tgoto out;\n+\t}\n+\n \tdev = dev_get_by_index_rcu(nft_net(pkt), oif);\n \tif (dev == NULL) {\n \t\tverdict = NF_DROP;\n@@ -170,7 +176,9 @@ static void nft_fwd_neigh_eval(const struct nft_expr *expr,\n \n \tskb->dev = dev;\n \tskb_clear_tstamp(skb);\n+\t(*nf_dup_skb_recursion)++;\n \tneigh_xmit(neigh_table, dev, addr, skb);\n+\t(*nf_dup_skb_recursion)--;\n out:\n \tregs->verdict.code = verdict;\n }\n","prefixes":["nf","v6","3/3"]}