{"id":2225884,"url":"http://patchwork.ozlabs.org/api/patches/2225884/?format=json","web_url":"http://patchwork.ozlabs.org/project/netfilter-devel/patch/20260421181652.161719-3-pablo@netfilter.org/","project":{"id":26,"url":"http://patchwork.ozlabs.org/api/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,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20260421181652.161719-3-pablo@netfilter.org>","list_archive_url":null,"date":"2026-04-21T18:16:52","name":"[nf,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":"8320722c6cf2efcd14103d91f3a4dac6d534981c","submitter":{"id":1315,"url":"http://patchwork.ozlabs.org/api/people/1315/?format=json","name":"Pablo Neira Ayuso","email":"pablo@netfilter.org"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/netfilter-devel/patch/20260421181652.161719-3-pablo@netfilter.org/mbox/","series":[{"id":500865,"url":"http://patchwork.ozlabs.org/api/series/500865/?format=json","web_url":"http://patchwork.ozlabs.org/project/netfilter-devel/list/?series=500865","date":"2026-04-21T18:16:51","name":"[nf,1/3] netfilter: replace skb_try_make_writable() by skb_ensure_writable()","version":1,"mbox":"http://patchwork.ozlabs.org/series/500865/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2225884/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2225884/checks/","tags":{},"related":[],"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=v9i+cYKl;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c04:e001:36c::12fc:5321; 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t=1776795427; c=relaxed/simple;\n\tbh=/YUh5XHOtUIgcUqDAwMhUMmnophTt7Um0NN0XI197WE=;\n\th=From:To:Subject:Date:Message-ID:In-Reply-To:References:\n\t MIME-Version;\n b=logxlKjhw+CO8uFrmjyc59jHSCbKJJXeUu0tnMD7IZfTutq4GuJ5Wwc4wGJwxH9cqb4146XLuGGZFRUKsHPZKY5EZQL1SpoU1/DV2AxetxGfcbu5BeCbcBNDVekVOfKvg29ZfbshqcQkYq8dYKj6j615pAD3GxatNf/Z0USS4vE=","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=v9i+cYKl; 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=1776795418;\n\tbh=/8lu3xgNOu26KIqyIV/ovhUuuonLToSPSq6JAw3raF0=;\n\th=From:To:Subject:Date:In-Reply-To:References:From;\n\tb=v9i+cYKl66E7dfJYIWstt+YtqnbjnS9ekc712dR2knHESTr5xRRm6h28Flzy7diN4\n\t 51rDK2yAXl9RmTXy5oGvX1IjbJcOtr8Bq1FZLqQGKi8PAbDRRZIfqekmnIaEq3m2He\n\t R5q2jWEWwGCtV3hqPkEUB7i3x3hUgt0L6kcjpQS3z6Q/JfcgR/KIYXqA1BOXmnM84q\n\t 7SU800tf9rNbBdKo5SFVt1cSoVD+/9CYWTZmF0m3TT4XPYYpBjSPC/jatP1IPssGq0\n\t yLin5obx48xk1Jl9Cz/JqsdOZ/Hokjp2XciZWL5VuLt4VpKVl17mLVrkGsz5ahibj0\n\t QAZ5UNedWHyoQ==","From":"Pablo Neira Ayuso ","To":"netfilter-devel@vger.kernel.org","Subject":"[PATCH nf 3/3] netfilter: nft_fwd_netdev: use recursion counter in\n neigh egress path","Date":"Tue, 21 Apr 2026 20:16:52 +0200","Message-ID":"<20260421181652.161719-3-pablo@netfilter.org>","X-Mailer":"git-send-email 2.47.3","In-Reply-To":"<20260421181652.161719-1-pablo@netfilter.org>","References":"<20260421181652.161719-1-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\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---\n include/net/netfilter/nf_dup_netdev.h | 13 +++++++++++++\n net/netfilter/nf_dup_netdev.c | 16 ----------------\n net/netfilter/nft_fwd_netdev.c | 7 +++++++\n 3 files changed, 20 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 8b6394660d1b..1feb2aa43191 100644\n--- a/net/netfilter/nft_fwd_netdev.c\n+++ b/net/netfilter/nft_fwd_netdev.c\n@@ -151,6 +151,11 @@ static void nft_fwd_neigh_eval(const struct nft_expr *expr,\n \t\tgoto out;\n \t}\n \n+\tif (*nf_get_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@@ -159,7 +164,9 @@ static void nft_fwd_neigh_eval(const struct nft_expr *expr,\n \n \tskb->dev = dev;\n \tskb_clear_tstamp(skb);\n+\t(*nf_get_nf_dup_skb_recursion())++;\n \tneigh_xmit(neigh_table, dev, addr, skb);\n+\t(*nf_get_nf_dup_skb_recursion())--;\n out:\n \tregs->verdict.code = verdict;\n }\n","prefixes":["nf","3/3"]}