From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 1859C3B47EB; Mon, 23 Mar 2026 14:00:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774274443; cv=none; b=mrFtqd8slostQhSrbZuKVtnU3Ul9msU9OKpIRjlp/I3dDvb1zVNCDNfTfKZ4MqSiB9eVcjsLeBUqLl7SKBzEdu8PwAc4reS0yOqHim44z8PxSb+/gV0Ol/qSZBtkb+DyokvE0cXMHSu64sEfb8haV00KVcI0fZabPPBrgIxtRcQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774274443; c=relaxed/simple; bh=X36AgmuPdaGYTI8tBwAPrJXihaZiE0No5XPPI0htbPg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qCIDAv5Bx2Kl3magBdx9lmmnuu9SgxMfJk9a/L0l3NbcySpSZFxFKp4V+eKvJa4AIE9OHMQbrKD3Db/7qNBo1tINu1gVtt8/zpUGGhEthP3V+4YQaON/rwLvfreU3rqBlSndP2AGpFjP5okTYL2m48OC4U1zEB7PGaR5i8p7QAM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zvKJgI++; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="zvKJgI++" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 917CBC4CEF7; Mon, 23 Mar 2026 14:00:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774274443; bh=X36AgmuPdaGYTI8tBwAPrJXihaZiE0No5XPPI0htbPg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zvKJgI+++oLBNRMj6torV5dwDWMKqsLMA4JQnd/lHIiDoEfPSuSd0AZbN8W75whWF DxoQqZEnKbrdI81XHXdP6GQ6cXr3jPuLKlGUgaXJbbSPMx61nhw2ZBYpF16dl4xUt9 L2UlRO6ScNlJHtureXG2WkpLHrjay0vF2oqg8h80= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Xiang Mei , Weiming Shi , Florian Westphal , Sasha Levin Subject: [PATCH 6.19 175/220] nfnetlink_osf: validate individual option lengths in fingerprints Date: Mon, 23 Mar 2026 14:45:52 +0100 Message-ID: <20260323134510.108743626@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260323134504.575022936@linuxfoundation.org> References: <20260323134504.575022936@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Weiming Shi [ Upstream commit dbdfaae9609629a9569362e3b8f33d0a20fd783c ] nfnl_osf_add_callback() validates opt_num bounds and string NUL-termination but does not check individual option length fields. A zero-length option causes nf_osf_match_one() to enter the option matching loop even when foptsize sums to zero, which matches packets with no TCP options where ctx->optp is NULL: Oops: general protection fault KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98) Call Trace: nf_osf_match (net/netfilter/nfnetlink_osf.c:227) xt_osf_match_packet (net/netfilter/xt_osf.c:32) ipt_do_table (net/ipv4/netfilter/ip_tables.c:293) nf_hook_slow (net/netfilter/core.c:623) ip_local_deliver (net/ipv4/ip_input.c:262) ip_rcv (net/ipv4/ip_input.c:573) Additionally, an MSS option (kind=2) with length < 4 causes out-of-bounds reads when nf_osf_match_one() unconditionally accesses optp[2] and optp[3] for MSS value extraction. While RFC 9293 section 3.2 specifies that the MSS option is always exactly 4 bytes (Kind=2, Length=4), the check uses "< 4" rather than "!= 4" because lengths greater than 4 do not cause memory safety issues -- the buffer is guaranteed to be at least foptsize bytes by the ctx->optsize == foptsize check. Reject fingerprints where any option has zero length, or where an MSS option has length less than 4, at add time rather than trusting these values in the packet matching hot path. Fixes: 11eeef41d5f6 ("netfilter: passive OS fingerprint xtables match") Reported-by: Xiang Mei Signed-off-by: Weiming Shi Signed-off-by: Florian Westphal Signed-off-by: Sasha Levin --- net/netfilter/nfnetlink_osf.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/net/netfilter/nfnetlink_osf.c b/net/netfilter/nfnetlink_osf.c index c0fc431991e88..9fc9544d4bc53 100644 --- a/net/netfilter/nfnetlink_osf.c +++ b/net/netfilter/nfnetlink_osf.c @@ -302,7 +302,9 @@ static int nfnl_osf_add_callback(struct sk_buff *skb, { struct nf_osf_user_finger *f; struct nf_osf_finger *kf = NULL, *sf; + unsigned int tot_opt_len = 0; int err = 0; + int i; if (!capable(CAP_NET_ADMIN)) return -EPERM; @@ -318,6 +320,17 @@ static int nfnl_osf_add_callback(struct sk_buff *skb, if (f->opt_num > ARRAY_SIZE(f->opt)) return -EINVAL; + for (i = 0; i < f->opt_num; i++) { + if (!f->opt[i].length || f->opt[i].length > MAX_IPOPTLEN) + return -EINVAL; + if (f->opt[i].kind == OSFOPT_MSS && f->opt[i].length < 4) + return -EINVAL; + + tot_opt_len += f->opt[i].length; + if (tot_opt_len > MAX_IPOPTLEN) + return -EINVAL; + } + if (!memchr(f->genre, 0, MAXGENRELEN) || !memchr(f->subtype, 0, MAXGENRELEN) || !memchr(f->version, 0, MAXGENRELEN)) -- 2.51.0