{"id":2223079,"url":"http://patchwork.ozlabs.org/api/1.0/patches/2223079/?format=json","project":{"id":26,"url":"http://patchwork.ozlabs.org/api/1.0/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":"<20260414111722.6944-1-pablo@netfilter.org>","date":"2026-04-14T11:17:22","name":"[nf] netfilter: nfnetlink_osf: fix divide-by-zero in OSF_WSS_MODULO","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"f1d5b4e4b4627d38e66df8d0ef599c4daf9654b2","submitter":{"id":1315,"url":"http://patchwork.ozlabs.org/api/1.0/people/1315/?format=json","name":"Pablo Neira Ayuso","email":"pablo@netfilter.org"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/netfilter-devel/patch/20260414111722.6944-1-pablo@netfilter.org/mbox/","series":[{"id":499820,"url":"http://patchwork.ozlabs.org/api/1.0/series/499820/?format=json","date":"2026-04-14T11:17:22","name":"[nf] netfilter: nfnetlink_osf: fix divide-by-zero in OSF_WSS_MODULO","version":1,"mbox":"http://patchwork.ozlabs.org/series/499820/mbox/"}],"check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2223079/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=QHjVXbzk;\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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t=1776165449; c=relaxed/simple;\n\tbh=vCdfaW9akuSEUpT3dkrjHG7m4BNmGyZtjh6I7q+cFOA=;\n\th=From:To:Cc:Subject:Date:Message-ID:MIME-Version;\n b=LpjAhUjjDGOTDZVI6YRE8Urckyn4bjDn6FH1d3INr/OXP4088acJtjkTRv27vCth3liof2fwMzETUGPiX/QvhzL5lS7driBPRp5WFNToSQuVgtEWoJIPZ3jCIEuLEsyXPF+LDmaE1jC/iT1U66MOm7sdjQuio1pYXcz/HWf50v4=","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=QHjVXbzk; 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=1776165446;\n\tbh=TW/05Cad82CW+FmpDAPNt1XPirSEQeexMK7TY5O/ukE=;\n\th=From:To:Cc:Subject:Date:From;\n\tb=QHjVXbzklRRFXZMYmRiCl1n8mKTHH2zywSxgb/RqFp+6W+fZHskLRDqEoI5Z6/HT/\n\t vTQbldSgKA8z2jizGR4sBcCuM+JLRchLnIvlgRoJ9frhYYaueXbQpDqEGyBWaNHsXS\n\t jztgegea5kHtS4A1l/PX0sRXqg4p9+VbC8NacZB7nb0FH0kqHCbywgV2jNsJxHbzGh\n\t hYwV6fnecNMIbs/zMah5FqYY0fbANIZkwPR5K8D2JVhIuk8gM/kugP7llUrgryCsFB\n\t Vm/gx3frqrpT3jTdVodAXuXYMepCfUIK1sbVPCe+4b6UTewDo9WOlxVF9ZGnhLS4J1\n\t z9+EgP4UvxQFA==","From":"Pablo Neira Ayuso ","To":"netfilter-devel@vger.kernel.org","Cc":"xmei5@asu.edu,\n\tfw@strlen.de","Subject":"[PATCH nf] netfilter: nfnetlink_osf: fix divide-by-zero in\n OSF_WSS_MODULO","Date":"Tue, 14 Apr 2026 13:17:22 +0200","Message-ID":"<20260414111722.6944-1-pablo@netfilter.org>","X-Mailer":"git-send-email 2.47.3","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":"Xiang Mei says:\n\nThe OSF_WSS_MODULO branch in nf_osf_match_one() performs:\n\n ctx->window % f->wss.val\n\nwithout guarding against f->wss.val == 0. A user with CAP_NET_ADMIN\ncan add an OSF fingerprint with wss.wc = OSF_WSS_MODULO and wss.val = 0\nvia nfnetlink. When a matching TCP SYN packet arrives, the kernel\nexecutes a division by zero and panics.\n\nThe OSF_WSS_PLAIN case already treats val == 0 as a wildcard (match\neverything). Apply the same semantics to OSF_WSS_MODULO: if val is 0,\nany window value matches rather than dividing by zero.\n\nCrash:\n Oops: divide error: 0000 [#1] SMP KASAN NOPTI\n RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98)\n Call Trace:\n \n nf_osf_match (net/netfilter/nfnetlink_osf.c:220 (discriminator 6))\n xt_osf_match_packet (net/netfilter/xt_osf.c:32)\n ipt_do_table (net/ipv4/netfilter/ip_tables.c:348)\n nf_hook_slow (net/netfilter/core.c:622 (discriminator 1))\n ip_local_deliver (net/ipv4/ip_input.c:265)\n ip_rcv (include/linux/skbuff.h:1162)\n __netif_receive_skb_one_core (net/core/dev.c:6181)\n process_backlog (.include/linux/skbuff.h:2502 net/core/dev.c:6642)\n __napi_poll (net/core/dev.c:7710)\n net_rx_action (net/core/dev.c:7945)\n handle_softirqs (kernel/softirq.c:622\n\nFix this from control plane, reject f->wss.val == 0 if wss.ws is\nOSF_WSS_MODULO.\n\nFixes: 11eeef41d5f6 (\"netfilter: passive OS fingerprint xtables match\")\nReported-by: Xiang Mei \nSigned-off-by: Pablo Neira Ayuso \n---\nApologies, I don't mean to step on your feet with this patch.\nThis just expedites scrutiny before PR submission.\n\n net/netfilter/nfnetlink_osf.c | 9 +++++++++\n 1 file changed, 9 insertions(+)","diff":"diff --git a/net/netfilter/nfnetlink_osf.c b/net/netfilter/nfnetlink_osf.c\nindex 5d15651c74f0..bf47a3812910 100644\n--- a/net/netfilter/nfnetlink_osf.c\n+++ b/net/netfilter/nfnetlink_osf.c\n@@ -329,6 +329,15 @@ static int nfnl_osf_add_callback(struct sk_buff *skb,\n \t\tif (f->opt[i].kind == OSFOPT_MSS && f->opt[i].length < 4)\n \t\t\treturn -EINVAL;\n \n+\t\tswitch (f->wss.wc) {\n+\t\tcase OSF_WSS_MODULO:\n+\t\t\tif (f->wss.val == 0)\n+\t\t\t\treturn -EINVAL;\n+\t\t\tbreak;\n+\t\tdefault:\n+\t\t\tbreak;\n+\t\t}\n+\n \t\ttot_opt_len += f->opt[i].length;\n \t\tif (tot_opt_len > MAX_IPOPTLEN)\n \t\t\treturn -EINVAL;\n","prefixes":["nf"]}