From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 CD6991A38F9; Fri, 26 Jun 2026 06:52:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782456741; cv=none; b=DnAEjMmXR6yOTYYsQ0bBiRHuC/h8s3nHm3UnJdB4Q4oeqRH0YwQt9ZxMkIsfgChyXOp2Med2+ocOsv9b3Tx+/H3DdWHPgpGEQswm5MrsR1riQuW+UyQPR+ZVImibn1vot3iu8slHK0El1wekTVkZzgKw1189SjmeZ3O05fO6u+M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782456741; c=relaxed/simple; bh=f15NUJf2D8gd3Uz7i/TVeIpGoFG6ZaBR8N9+UBH5I7I=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=u1D8fhYdznYKwrGtcoQ2Q3BgHRDS5Y1uN3CinctCSL8Z0rm/MZLGMTgLNA+fx23EgnU2IaaSTDWSD41Hsxzcn+7dGiQA7k2FyPwuh/wjbX8+aSOZFjB8AIgUnVrqKO/uWobAkC8TQN0fdWug/Nfssww8m62h/hzWag6ogzSzaB8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=2tjalHeR; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="2tjalHeR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 812FE1F00A3A; Fri, 26 Jun 2026 06:52:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1782456738; bh=FNa5qRwhRr6rryVW7TDlnD7K0wtIjPsL5cMW4Y31S24=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=2tjalHeRT7aBQocMURvgN2j7iBuRFOLN9actXuzaCNWwT2DQ1K1I9uJZglEio5Dv+ 57oA40zqDE3Aqtb/G4LNCZSCA/3u9BYtyRQ3qoClTP/9eslISDYSxay/vc5coDFM4S J8dbh/MFue4QvKQbhxYhfNWwLU0Y1ltQi3kzE5eY= Date: Fri, 26 Jun 2026 07:51:05 +0100 From: Greg KH To: Alexander Martyniuk Cc: sashal@kernel.org, bestswngs@gmail.com, coreteam@netfilter.org, davem@davemloft.net, fw@strlen.de, kaber@trash.net, kadlec@netfilter.org, kuba@kernel.org, kuznet@ms2.inr.ac.ru, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, netfilter-devel@vger.kernel, pablo@netfilter.org, stable@vger.kernel.org, xmei5@asu.edu, yoshfuji@linux-ipv6.org Subject: Re: [PATCH v2] netfilter: nf_log: validate MAC header was set before dumping it Message-ID: <2026062658-pregame-buggy-ccbc@gregkh> References: <20260625054005.0003.nflog-510@kernel.org> <20260625164755.161383-1-alexevgmart@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260625164755.161383-1-alexevgmart@gmail.com> On Thu, Jun 25, 2026 at 07:47:55PM +0300, Alexander Martyniuk wrote: > From: Xiang Mei > > commit a84b6fedbc97078788be78dbdd7517d143ad1a77 upstream. > > The fallback path of dump_mac_header() guards the MAC header access > only with "skb->mac_header != skb->network_header", without checking > skb_mac_header_was_set(). When the MAC header is unset, mac_header is > 0xffff, so the test passes and skb_mac_header(skb) returns > skb->head + 0xffff, ~64 KiB past the buffer; the loop then reads > dev->hard_header_len bytes out of bounds into the kernel log. > > This is reachable via the netdev logger: nf_log_unknown_packet() calls > dump_mac_header() unconditionally, and an skb sent through AF_PACKET > with PACKET_QDISC_BYPASS reaches the egress hook with mac_header still > unset (__dev_queue_xmit(), which would reset it, is bypassed). > > Add the skb_mac_header_was_set() check the ARPHRD_ETHER path already > uses, and replace the open-coded MAC header length test with > skb_mac_header_len(). Only skbs with an unset MAC header are affected; > valid ones are dumped as before. > > BUG: KASAN: slab-out-of-bounds in dump_mac_header (net/netfilter/nf_log_syslog.c:831) > Read of size 1 at addr ffff88800ea49d3f by task exploit/148 > Call Trace: > kasan_report (mm/kasan/report.c:595) > dump_mac_header (net/netfilter/nf_log_syslog.c:831) > nf_log_netdev_packet (net/netfilter/nf_log_syslog.c:938 net/netfilter/nf_log_syslog.c:963) > nf_log_packet (net/netfilter/nf_log.c:260) > nft_log_eval (net/netfilter/nft_log.c:60) > nft_do_chain (net/netfilter/nf_tables_core.c:285) > nft_do_chain_netdev (net/netfilter/nft_chain_filter.c:307) > nf_hook_slow (net/netfilter/core.c:619) > nf_hook_direct_egress (net/packet/af_packet.c:257) > packet_xmit (net/packet/af_packet.c:280) > packet_sendmsg (net/packet/af_packet.c:3114) > __sys_sendto (net/socket.c:2265) > > Fixes: 7eb9282cd0ef ("netfilter: ipt_LOG/ip6t_LOG: add option to print decoded MAC header") > Reported-by: Weiming Shi > Assisted-by: Claude:claude-opus-4-8 > Signed-off-by: Xiang Mei > Signed-off-by: Pablo Neira Ayuso > Signed-off-by: Alexander Martyniuk > --- > net/ipv4/netfilter/nf_log_ipv4.c | 4 ++-- > net/ipv6/netfilter/nf_log_ipv6.c | 4 ++-- > 2 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/net/ipv4/netfilter/nf_log_ipv4.c b/net/ipv4/netfilter/nf_log_ipv4.c > index d07583fac8f8..d6164e8e2c73 100644 > --- a/net/ipv4/netfilter/nf_log_ipv4.c > +++ b/net/ipv4/netfilter/nf_log_ipv4.c > @@ -296,8 +296,8 @@ static void dump_ipv4_mac_header(struct nf_log_buf *m, > > fallback: > nf_log_buf_add(m, "MAC="); > - if (dev->hard_header_len && > - skb->mac_header != skb->network_header) { > + if (dev->hard_header_len && skb_mac_header_was_set(skb) && > + skb_mac_header_len(skb) != 0) { > const unsigned char *p = skb_mac_header(skb); > unsigned int i; > > diff --git a/net/ipv6/netfilter/nf_log_ipv6.c b/net/ipv6/netfilter/nf_log_ipv6.c > index 8210ff34ed9b..cc724870a467 100644 > --- a/net/ipv6/netfilter/nf_log_ipv6.c > +++ b/net/ipv6/netfilter/nf_log_ipv6.c > @@ -309,8 +309,8 @@ static void dump_ipv6_mac_header(struct nf_log_buf *m, > > fallback: > nf_log_buf_add(m, "MAC="); > - if (dev->hard_header_len && > - skb->mac_header != skb->network_header) { > + if (dev->hard_header_len && skb_mac_header_was_set(skb) && > + skb_mac_header_len(skb) != 0) { > const unsigned char *p = skb_mac_header(skb); > unsigned int len = dev->hard_header_len; > unsigned int i; > -- > 2.43.0 > > What kernel(s) is this for?