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GET /api/1.2/patches/2221279/?format=api
{ "id": 2221279, "url": "http://patchwork.ozlabs.org/api/1.2/patches/2221279/?format=api", "web_url": "http://patchwork.ozlabs.org/project/netfilter-devel/patch/20260409053629.698822-2-bestswngs@gmail.com/", "project": { "id": 26, "url": "http://patchwork.ozlabs.org/api/1.2/projects/26/?format=api", "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": "<20260409053629.698822-2-bestswngs@gmail.com>", "list_archive_url": null, "date": "2026-04-09T05:36:30", "name": "[nf] netfilter: nft_fwd_netdev: use recursion counter in neigh egress path", "commit_ref": null, "pull_url": null, "state": "changes-requested", "archived": true, "hash": "34ab5a94b39d5a5fb7c6c05f3793d1201add954a", "submitter": { "id": 92941, "url": "http://patchwork.ozlabs.org/api/1.2/people/92941/?format=api", "name": "Weiming Shi", "email": "bestswngs@gmail.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/netfilter-devel/patch/20260409053629.698822-2-bestswngs@gmail.com/mbox/", "series": [ { "id": 499237, "url": "http://patchwork.ozlabs.org/api/1.2/series/499237/?format=api", "web_url": "http://patchwork.ozlabs.org/project/netfilter-devel/list/?series=499237", "date": "2026-04-09T05:36:30", "name": "[nf] netfilter: nft_fwd_netdev: use recursion counter in neigh egress path", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/499237/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2221279/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2221279/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "\n <netfilter-devel+bounces-11751-incoming=patchwork.ozlabs.org@vger.kernel.org>", "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=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=VxKuQp8K;\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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Miller\" <davem@davemloft.net>,\n\tEric Dumazet <edumazet@google.com>,\n\tJakub Kicinski <kuba@kernel.org>,\n\tPaolo Abeni <pabeni@redhat.com>", "Cc": "Phil Sutter <phil@nwl.cc>,\n\tSimon Horman <horms@kernel.org>,\n\tnetfilter-devel@vger.kernel.org,\n\tcoreteam@netfilter.org,\n\tnetdev@vger.kernel.org,\n\tXiang Mei <xmei5@asu.edu>,\n\tWeiming Shi <bestswngs@gmail.com>", "Subject": "[PATCH nf] netfilter: nft_fwd_netdev: use recursion counter in neigh\n egress path", "Date": "Thu, 9 Apr 2026 13:36:30 +0800", "Message-ID": "<20260409053629.698822-2-bestswngs@gmail.com>", "X-Mailer": "git-send-email 2.43.0", "Precedence": "bulk", "X-Mailing-List": "netfilter-devel@vger.kernel.org", "List-Id": "<netfilter-devel.vger.kernel.org>", "List-Subscribe": "<mailto:netfilter-devel+subscribe@vger.kernel.org>", "List-Unsubscribe": "<mailto:netfilter-devel+unsubscribe@vger.kernel.org>", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit" }, "content": "nft_fwd_neigh_eval() can be attached to NF_NETDEV_EGRESS chains since\ncommit f87b9464d152 (\"netfilter: nft_fwd_netdev: Support egress hook\").\nWhen a forwarding rule targets the same device (or two devices forward\nto each other), the evaluator calls neigh_xmit() which reaches\ndev_queue_xmit(), re-entering nf_hook_egress() before the previous\ninvocation returns. This recurses until the kernel stack is exhausted.\n\nThe nf_dup_skb_recursion counter in nf_do_netdev_egress() was added by\ncommit fcd53c51d037 (\"netfilter: nf_dup_netdev: add and use recursion\ncounter\") to prevent exactly this class of bug, but nft_fwd_neigh_eval()\nbypasses that helper entirely by calling neigh_xmit() directly.\n\n BUG: KASAN: slab-out-of-bounds in nft_do_chain (net/netfilter/nf_tables_core.c:287)\n Call Trace:\n nft_do_chain (net/netfilter/nf_tables_core.c:287)\n nft_do_chain_netdev (net/netfilter/nft_chain_filter.c:289)\n nf_hook_slow (include/linux/netfilter.h:158)\n __dev_queue_xmit (net/core/dev.c:4807)\n neigh_resolve_output (include/linux/seqlock.h:392)\n neigh_xmit (net/core/neighbour.c:3230)\n nft_fwd_neigh_eval (net/netfilter/nft_fwd_netdev.c:150)\n nft_do_chain (net/netfilter/nf_tables_core.c:287)\n nft_do_chain_netdev (net/netfilter/nft_chain_filter.c:289)\n nf_hook_slow (include/linux/netfilter.h:158)\n __dev_queue_xmit (net/core/dev.c:4807)\n [repeats until stack exhaustion]\n\n Kernel panic - not syncing: Fatal exception in interrupt\n\nExport the recursion counter helpers from nf_dup_netdev and use them\nin nft_fwd_neigh_eval() to bound the recursion depth, matching the\nprotection already present in nf_do_netdev_egress().\n\nFixes: f87b9464d152 (\"netfilter: nft_fwd_netdev: Support egress hook\")\nReported-by: Xiang Mei <xmei5@asu.edu>\nSigned-off-by: Weiming Shi <bestswngs@gmail.com>\n---\n include/net/netfilter/nf_dup_netdev.h | 4 ++++\n net/netfilter/nf_dup_netdev.c | 18 ++++++++++++++++++\n net/netfilter/nft_fwd_netdev.c | 7 +++++++\n 3 files changed, 29 insertions(+)", "diff": "diff --git a/include/net/netfilter/nf_dup_netdev.h b/include/net/netfilter/nf_dup_netdev.h\nindex b175d271aec9..17362f76d1d1 100644\n--- a/include/net/netfilter/nf_dup_netdev.h\n+++ b/include/net/netfilter/nf_dup_netdev.h\n@@ -7,6 +7,10 @@\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+bool nf_dup_netdev_has_recursed(void);\n+void nf_dup_netdev_recursion_inc(void);\n+void nf_dup_netdev_recursion_dec(void);\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 fab8b9011098..e2fe8bb6fe0d 100644\n--- a/net/netfilter/nf_dup_netdev.c\n+++ b/net/netfilter/nf_dup_netdev.c\n@@ -29,6 +29,24 @@ static u8 *nf_get_nf_dup_skb_recursion(void)\n \n #endif\n \n+bool nf_dup_netdev_has_recursed(void)\n+{\n+\treturn *nf_get_nf_dup_skb_recursion() > NF_RECURSION_LIMIT;\n+}\n+EXPORT_SYMBOL_GPL(nf_dup_netdev_has_recursed);\n+\n+void nf_dup_netdev_recursion_inc(void)\n+{\n+\t(*nf_get_nf_dup_skb_recursion())++;\n+}\n+EXPORT_SYMBOL_GPL(nf_dup_netdev_recursion_inc);\n+\n+void nf_dup_netdev_recursion_dec(void)\n+{\n+\t(*nf_get_nf_dup_skb_recursion())--;\n+}\n+EXPORT_SYMBOL_GPL(nf_dup_netdev_recursion_dec);\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 152a9fb4d23a..d85f72af3589 100644\n--- a/net/netfilter/nft_fwd_netdev.c\n+++ b/net/netfilter/nft_fwd_netdev.c\n@@ -141,13 +141,20 @@ static void nft_fwd_neigh_eval(const struct nft_expr *expr,\n \t\tgoto out;\n \t}\n \n+\tif (nf_dup_netdev_has_recursed()) {\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\treturn;\n \n \tskb->dev = dev;\n \tskb_clear_tstamp(skb);\n+\tnf_dup_netdev_recursion_inc();\n \tneigh_xmit(neigh_table, dev, addr, skb);\n+\tnf_dup_netdev_recursion_dec();\n out:\n \tregs->verdict.code = verdict;\n }\n", "prefixes": [ "nf" ] }