From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.netfilter.org (mail.netfilter.org [217.70.190.124]) (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 E850A1DDC37 for ; Wed, 15 Apr 2026 09:55:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.190.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776246934; cv=none; b=DYVdd7+vWmfroc0FXmgc7hZyF/xtkJ2ZGSpES6yz+NIt8CWKg+H0y/+WVgCD4uYPadP6iHGlsBICwY3HxCgYT6aqiI275bf5W5mnUdgvGyLwgNNCJc312TEfnl6hPZqGG25+T65256paohIfXS3rZpCnDVsVpqCdxhKucf8zZTs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776246934; c=relaxed/simple; bh=NnOE/jo7PzoGIHhyFyqlI/69A/YCBZh2x347XKVH1MI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lJva2cnyiB2QaAeTPMqHiCZ52tdPxkhpQESueyNowRdIX4uB5FL2qo9q3JFJHzsFDkadBNnyhBS89RTFPtB59MAAXsjP+ZJ1biqelPivJm/6XmrnbcbglHEMaJ8h9gNzi5a4YyI5Kq0/8ucz0AqmX5SHr0DKOiY4/FHqAgZci3Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org; spf=pass smtp.mailfrom=netfilter.org; dkim=pass (2048-bit key) header.d=netfilter.org header.i=@netfilter.org header.b=oswYsteU; arc=none smtp.client-ip=217.70.190.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=netfilter.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=netfilter.org header.i=@netfilter.org header.b="oswYsteU" Received: from netfilter.org (mail-agni [217.70.190.124]) by mail.netfilter.org (Postfix) with UTF8SMTPSA id 014AE60177; Wed, 15 Apr 2026 11:55:31 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netfilter.org; s=2025; t=1776246931; bh=JaMxTj6ILXESUfmgJz+FNkPvQCKN/A5rJaO7Rk0gKxI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oswYsteUN3bJT5c2Ji0kfZHaqWN9EoKo6m4Sj4Y0mygtORawgKfLipipbu0oY1nOe QpnCH1r6r41aS3lcXFILm6TZSLBT+mCBig6qlndj3r5BbhutAMFSK8dlQp10o6c7un vj/XgFCktWdV7pajGafOVMlgEYdrMbj0f3h4ned1UdqyQsimYSij7i3GrBgsf6rUpo aW9GO05Phl9jdiuXgkVv5H/dF7q91f6AEfiDDYjilBij4J4cn/Lah5e2yj6K9/xyln ik3RuGHpX/r7vTPtvV3mfFpN9mJ2GttyJU4myQr9Xkmzo4JkwyjO/J4vVStlqQUKdG p0Z6sOAX1Luaw== Date: Wed, 15 Apr 2026 11:55:28 +0200 From: Pablo Neira Ayuso To: Xiang Mei Cc: netfilter-devel@vger.kernel.org, Florian Westphal , Phil Sutter , coreteam@netfilter.org, Weiming Shi Subject: Re: [PATCH nf v2] netfilter: nfnetlink_osf: fix divide-by-zero in OSF_WSS_MODULO Message-ID: References: <20260414221401.2809350-1-xmei5@asu.edu> Precedence: bulk X-Mailing-List: netfilter-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Wed, Apr 15, 2026 at 11:29:06AM +0200, Pablo Neira Ayuso wrote: > On Tue, Apr 14, 2026 at 03:14:01PM -0700, Xiang Mei wrote: > > nf_osf_match_one() computes ctx->window % f->wss.val in the > > OSF_WSS_MODULO branch with no guard for f->wss.val == 0. A > > CAP_NET_ADMIN user can add such a fingerprint via nfnetlink; a > > subsequent matching TCP SYN divides by zero and panics the kernel. > > > > Reject the bogus fingerprint in nfnl_osf_add_callback() above the > > per-option for-loop. f->wss is per-fingerprint, not per-option, so > > the check must run regardless of f->opt_num (including 0). Also > > reject wss.wc >= OSF_WSS_MAX; nf_osf_match_one() already treats that > > as "should not happen". > > > > Crash: > > Oops: divide error: 0000 [#1] SMP KASAN NOPTI > > RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98) > > Call Trace: > > > > nf_osf_match (net/netfilter/nfnetlink_osf.c:220) > > xt_osf_match_packet (net/netfilter/xt_osf.c:32) > > ipt_do_table (net/ipv4/netfilter/ip_tables.c:348) > > nf_hook_slow (net/netfilter/core.c:622) > > ip_local_deliver (net/ipv4/ip_input.c:265) > > ip_rcv (include/linux/skbuff.h:1162) > > __netif_receive_skb_one_core (net/core/dev.c:6181) > > process_backlog (net/core/dev.c:6642) > > __napi_poll (net/core/dev.c:7710) > > net_rx_action (net/core/dev.c:7945) > > handle_softirqs (kernel/softirq.c:622) > > > > Fixes: 11eeef41d5f6 ("netfilter: passive OS fingerprint xtables match") > > Reported-by: Weiming Shi > > Suggested-by: Florian Westphal > > Suggested-by: Pablo Neira Ayuso > > Signed-off-by: Xiang Mei > > --- > > v2: Fix the bug in configure path and correct the fix tag > > > > net/netfilter/nfnetlink_osf.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/net/netfilter/nfnetlink_osf.c b/net/netfilter/nfnetlink_osf.c > > index 45d9ad231..70172ca07 100644 > > --- a/net/netfilter/nfnetlink_osf.c > > +++ b/net/netfilter/nfnetlink_osf.c > > @@ -320,6 +320,10 @@ static int nfnl_osf_add_callback(struct sk_buff *skb, > > if (f->opt_num > ARRAY_SIZE(f->opt)) > > return -EINVAL; > > > > + if (f->wss.wc >= OSF_WSS_MAX || > > + (f->wss.wc == OSF_WSS_MODULO && f->wss.val == 0)) > > + return -EINVAL; > > Maybe, more explicit, it is more lengthy but cristal clear: Not really, this needs to be done out of loop as you do. I'll take your patch, thanks!