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 5837B31B828 for ; Sun, 8 Mar 2026 11:11:57 +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=1772968318; cv=none; b=uQhzI3R0X/kpHPyjzBsrh1vwl8n3h0kFQFISsczEPhGNv55jTb33r3ZHH5igGW774TsOyLgaZ5KirUNdo3hhIDQ0iK0g4hdkXR07ZxaR9Tg8GTMVKQ3OuyZqermSnRy7kuV3CM0kfGnVVpXYwLeDbX0PZoYotR2tqNq4d7GOsdU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772968318; c=relaxed/simple; bh=gkGefTtxzZrHQY+k55TdJmonoALHIeC7Wek/bXNJHto=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=TAdGBCCs/BK5zFoe234xiXZepx2JMT+sbhxoGYudaHGaD9hCXhPkvf7/O2/DuR8bTb/xtR20OWNFAztbet69BRFVLq9vTGLc0NQHIXfEdTQ/0frz4zY7pIs5+xzcxEF8ojdsojoe47+jZ4R5OJmgoKpWkyZmZksBTZoQO0IhMmo= 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=koCjqqC7; 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="koCjqqC7" Received: from netfilter.org (mail-agni [217.70.190.124]) by mail.netfilter.org (Postfix) with UTF8SMTPSA id 75C276017C; Sun, 8 Mar 2026 12:11:55 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netfilter.org; s=2025; t=1772968315; bh=kQpFah0Pwve5BgHQhHos1QBe8H7wkPEBsqa/4UrwjC4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=koCjqqC7m/L+jg5uyWmKd1QM9mZTn4xqgefjAK7T3smKseuSEDjI+ZtUdMiKCQefA IrXf4ditai1s5SDa2H9po/kY64rep7hKogFImuzlEQWPevMFRsrW0gUblqLjqCoHiM kciLC4kMoLpb5HXnVyER/a4bSXcrhiRDSG3eyqlgT4vhZe4cdq1fGyA4DpqnM0Pw1G j52uspXGF4h7bBr0y2G2ORvk3ndToq6nggTuE70pjg24phsnpomu+E/uAkwxfqbYLP ae5Vfdzx0HtbufaKKDSDj55jCzJPHxorBx2BDZx13ebWpKTh/tITWKy1uoiBSMVyl/ rd/IO1hHuM6EA== Date: Sun, 8 Mar 2026 12:11:53 +0100 From: Pablo Neira Ayuso To: David Dull Cc: netfilter-devel@vger.kernel.org, fw@strlen.de Subject: Re: [PATCH v2] netfilter: guard option walkers against 1-byte tail reads Message-ID: References: <20260307182621.1315-1-monderasdor@gmail.com> <20260307184553.1779-1-monderasdor@gmail.com> 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: <20260307184553.1779-1-monderasdor@gmail.com> On Sat, Mar 07, 2026 at 08:45:52PM +0200, David Dull wrote: > When the last byte of options is a non-single-byte option kind, walkers > that advance with i += op[i + 1] ? : 1 can read op[i + 1] past the end > of the option area. > > Add an explicit i == optlen - 1 check before dereferencing op[i + 1] > in xt_tcpudp and xt_dccp option walkers. > > Fixes: 2e4e6a17af35 ("[NETFILTER] x_tables: Abstraction layer for {ip,ip6,arp}_tables") > Cc: fw@strlen.de > Cc: stable@vger.kernel.org > Signed-off-by: David Dull > --- > net/netfilter/xt_dccp.c | 4 ++-- > net/netfilter/xt_tcpudp.c | 6 ++++-- > 2 files changed, 5 insertions(+), 4 deletions(-) > > diff --git a/net/netfilter/xt_dccp.c b/net/netfilter/xt_dccp.c > index e5a13ecbe6..037ab93e25 100644 > --- a/net/netfilter/xt_dccp.c > +++ b/net/netfilter/xt_dccp.c > @@ -62,10 +62,10 @@ dccp_find_option(u_int8_t option, > return true; > } > > - if (op[i] < 2) > + if (op[i] < 2 || i == optlen - 1) > i++; > else > - i += op[i+1]?:1; > + i += op[i + 1] ? : 1; > } To improve this area, I'd suggest: if (op[i] < 2) { i++; continue; } if (i + 1 >= optlen) break; i += op[i + 1] ? : 1; }