From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yx2-f13.google.com (mail-yx2-f13.google.com [74.125.224.141]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6BE09388391 for ; Tue, 22 Sep 2026 03:03:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.224.141 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790046203; cv=none; b=aEyfYJoxUAg1hwy2RF1FsMlDCIo/Cx400avaLkY/CJ+6Wn8l3oGtWEIjJ58XGCZBvp7LVJOFWnIyXQ6qxWD5CoWBTsbERc8brtAVN7iTCHE8VXgM04qeUJMNp7XeV0g9fPB197aFwLS6twDvjmuGAAwM8790Pc1H5ubh0U3HW3Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790046203; c=relaxed/simple; bh=xxPCfoW71C+dY5Vk73+EVbPgQd5ga8fAuuMpvs44aSA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=esBXNEBlUATUNPW0/AipyF+nuhWRm0+29y7OK2da3ONiexzoRTSsa9pBZn5dwsMLWIRWS5nYCbqkHqVDj0raMqoDh0je8yVgSX++n2/ew1sVXI3dzD9B8r2z1Hsvfx5a79u9NfGQQ8d1pDYTtUdWJ8pAGM5OsNvb0xCwa5ijT7U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Qh+Elqvl; arc=none smtp.client-ip=74.125.224.141 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Qh+Elqvl" Received: by mail-yx2-f13.google.com with SMTP id 956f58d0204a3-66e4ab20a33so3756079d50.1 for ; Mon, 21 Sep 2026 20:03:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1790046200; x=1790651000; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=B5rs7+ILfA3J/8r3zuBgSBRVCSTxSnXx2oYi6bmrhLI=; b=Qh+Elqvl8Z+LZ9x6Jhh8EPOVxKwCr38xJ5hf/CvPrLrahEy8nlF+Hw+JbxmuilcEmh KBoTBLvy9b8EgOgmAe6snoUat1GLn32ck5dl3BW0l7eKvH4X8eSmM7bCLpLNHTpzv7Pq q3mCwfa/BFFAtE9GM7hMrTPfnJiTl7+LJhkkl4/FRd5MjiySuUiSVMSF6u9XAK68tHAX KP6lCmEr/KzPVnHwnNvNho93MCcyC5uMMjdgYlw2bEz2XyOLeVQgBYvjac7n0d6l4Twm 27kkfNnGymTimznSHf25G+rAWc4q4ec3gtolnEK/3eBeIYgjHewXbreBW+euyJt60qlf Y7qQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790046200; x=1790651000; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=B5rs7+ILfA3J/8r3zuBgSBRVCSTxSnXx2oYi6bmrhLI=; b=cZh7YGaP9BAaFSbPsKYQDsBBWGfz8uZNxgoLK4To21at2cxwvLkCdD28rF9jZLz94t NOO00uMdeWSq7fjgYLxUhrHkPb6BygzFqEzJ7vcxxGn9i0OgyR3V09JmQcxSXFipQH8r g6uJv8SplsMgzYGjMWUXtlMDHk2kzZrnZqHj1B9xe2aQlWSX8dreEYbHjNqUhi2IbLj2 CpWdRSEMwk9B/eT2pvBN/jIz1bwty6M9S5hsAfNtPYhZiZxNzIhhSPFnJmG89xZSYY89 TUrQtcWmJ4OTOD+jeJCF7YXJUBI5DsTHvsmvaRbwTxwAIeMyzl5U6AKA4vGo6l2rH4+6 NsNg== X-Forwarded-Encrypted: i=1; AKwUvBzAQXNFOHBYeVLCn2itunrKGpsl00EbkY168VQqn7buB7HvQi5Y7cNiaMEXgt/0Groi2qBHP7tOZvMrbgYE1UU=@vger.kernel.org X-Gm-Message-State: AFuF++mwQJvvSlV+rYMcLxO1SNVFZn+8q7/4aMW3SDWFjGMeG2ELu+Td 1v4JpW+hyToANK5v3RwgD/uAEk3to0hMgsvk5B3dxgOwmFxdEhV8qmb1 X-Gm-Gg: AYBFou0cQCbfTehp7PzCiNLo5L+Fv9kBS2GCaA8NJE8J6SfdtP/soeLxPZrhHVmKHGO dWrRqsi17hWKHVEkw1zv8zZ5CmAKTjWWH60iXvStH684uvm6dKCzL/jyRmAUTc3QSx/EA1VkANI ZtLYhRIdgyuVGCLUYqUAfAmcM8xfbsc7+LDB01wkvPfGK7HPJ4yHxozqsjr74TrZEQFlUVs+ryf 7pKZb0IqHhfUKBSumjpOw86Ylil8yisiz80rlTI8mmRzvOgpJ07v9DdEYYiHZzuE1nrlb0zegms MCiOZP9J3tVNbdccVr7o+W6Mwl13Wyo1/IXiN5ijFEYUK62Wy5hN5UYWwMsWm5DMd4T/b4SgXg8 wiG9c4AaQHLZ+VXJsELycl0lDN6Y1z0fC1pUMJhlNHqIqNgJW768qaW2k5pv56ViuchmZj6/b4P pNeR+RECq3neFZ83dO7lSVQiv0trwR8/5fposPv6Q7klMkuDu5gLrsrLnzTGihIAZIhhTckFwDF PB3XbrElPK/xTM3paRPzlRypvVFvWw+w6ubKWWVm3d3k9ZmV2sbOD4QtpXAzOlgmvxVoZEv X-Received: by 2002:a05:690e:138d:b0:668:1c09:aef1 with SMTP id 956f58d0204a3-6717fc7e75dmr3816179d50.6.1790046200291; Mon, 21 Sep 2026 20:03:20 -0700 (PDT) Received: from localhost.localdomain ([2601:155:4200:2c80:2875:43a3:e345:710c]) by smtp.gmail.com with ESMTPSA id 00721157ae682-8a2c1b02abdsm1471447b3.17.2026.09.21.20.03.18 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 21 Sep 2026 20:03:19 -0700 (PDT) From: Paulos Yibelo To: netdev@vger.kernel.org Cc: richard@nod.at, anton.ivanov@cambridgegreys.com, johannes@sipsolutions.net, willemdebruijn.kernel@gmail.com, jasowangio@gmail.com, mst@redhat.com, eperezma@redhat.com, xuanzhuo@linux.alibaba.com, andrew+netdev@lunn.ch, pablo@netfilter.org, fw@strlen.de, phil@nwl.cc, razor@blackwall.org, idosch@nvidia.com, dsahern@kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, linux-um@lists.infradead.org, virtualization@lists.linux.dev, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, bridge@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH net v6 2/2] ip: reject partial checksums covering network headers Date: Mon, 21 Sep 2026 23:03:10 -0400 Message-ID: <20260922030310.8684-3-habte.yibelo@gmail.com> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20260922030310.8684-1-habte.yibelo@gmail.com> References: <20260922030310.8684-1-habte.yibelo@gmail.com> Precedence: bulk X-Mailing-List: netfilter-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ip_do_fragment() and nf_br_ip_fragment() complete a CHECKSUM_PARTIAL skb before reading the IPv4 header length. ip6_fragment() and br_ip6_fragment() complete one after parsing the IPv6 header chain. A virtualization interface can supply a checksum start which, after link-layer removal, still points inside that parsed network header. skb_checksum_help() then writes the completed checksum into header bytes the stack has already consumed. For IPv4, changing iph->ihl after routing and validation can make fragmentation copy beyond the skb's logical linear head into transmitted options. A negative checksum-start offset is rejected by skb_checksum_help(), but only after a WARN_ONCE which can panic a panic_on_warn system. Validate the checksum start against the parsed header length before completing it. For IPv4, read and validate IHL first, retain it, and reacquire iph after skb_checksum_help() in both implementations. For IPv6, use the length returned by ip6_find_1stfragopt() in both implementations. Compare the signed checksum-start offset with the bounded signed header length so integer promotion cannot bypass either boundary. Fixes: dbd3393c56a8 ("ipv4: add defensive check for CHECKSUM_PARTIAL skbs in ip_fragment") Fixes: 405c92f7a541 ("ipv6: add defensive check for CHECKSUM_PARTIAL skbs in ip_fragment") Fixes: 3c171f496ef5 ("netfilter: bridge: add connection tracking system") Fixes: 764dd163ac92 ("netfilter: nf_conntrack_bridge: add support for IPv6") Reported-by: Paulos Yibelo Link: https://lore.kernel.org/netdev/20260920004733.6473-3-habte.yibelo@gmail.com/ Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Paulos Yibelo --- net/bridge/netfilter/nf_conntrack_bridge.c | 21 +++++++++++++++----- net/ipv4/ip_output.c | 23 ++++++++++++++++------ net/ipv6/ip6_output.c | 12 ++++++++--- net/ipv6/netfilter.c | 12 ++++++++--- 4 files changed, 51 insertions(+), 17 deletions(-) diff --git a/net/bridge/netfilter/nf_conntrack_bridge.c b/net/bridge/netfilter/nf_conntrack_bridge.c index 7ecb8a26b..d81ed8692 100644 --- a/net/bridge/netfilter/nf_conntrack_bridge.c +++ b/net/bridge/netfilter/nf_conntrack_bridge.c @@ -38,18 +38,29 @@ static int nf_br_ip_fragment(struct net *net, struct sock *sk, struct iphdr *iph; int err = 0; - /* for offloaded checksums cleanup checksum before fragmentation */ - if (skb->ip_summed == CHECKSUM_PARTIAL && - (err = skb_checksum_help(skb))) + iph = ip_hdr(skb); + hlen = iph->ihl * 4; + if (unlikely(hlen < sizeof(*iph) || hlen > skb_headlen(skb))) { + err = -EINVAL; goto blackhole; + } - iph = ip_hdr(skb); + /* Complete offloaded checksums only after the validated IP header. */ + if (skb->ip_summed == CHECKSUM_PARTIAL) { + if (unlikely(skb_checksum_start_offset(skb) < (int)hlen)) { + err = -EINVAL; + goto blackhole; + } + err = skb_checksum_help(skb); + if (err) + goto blackhole; + iph = ip_hdr(skb); + } /* * Setup starting values */ - hlen = iph->ihl * 4; frag_max_size -= hlen; ll_rs = LL_RESERVED_SPACE(skb->dev); mtu = skb->dev->mtu; diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index a24cc8ee1..fa6a74d20 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -770,16 +770,28 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, struct ip_frag_state state; int err = 0; - /* for offloaded checksums cleanup checksum before fragmentation */ - if (skb->ip_summed == CHECKSUM_PARTIAL && - (err = skb_checksum_help(skb))) - goto fail; - /* * Point into the IP datagram header. */ iph = ip_hdr(skb); + hlen = iph->ihl * 4; + if (unlikely(hlen < sizeof(*iph) || hlen > skb_headlen(skb))) { + err = -EINVAL; + goto fail; + } + + /* Complete offloaded checksums only after the validated IP header. */ + if (skb->ip_summed == CHECKSUM_PARTIAL) { + if (unlikely(skb_checksum_start_offset(skb) < (int)hlen)) { + err = -EINVAL; + goto fail; + } + err = skb_checksum_help(skb); + if (err) + goto fail; + iph = ip_hdr(skb); + } mtu = ip_skb_dst_mtu(sk, skb); if (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size < mtu) @@ -789,7 +801,6 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, * Setup starting values. */ - hlen = iph->ihl * 4; if (mtu < hlen + 8) { err = -EMSGSIZE; goto fail; diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 550965058..d157b6ade 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -942,9 +942,15 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, frag_id = ipv6_select_ident(net, &ipv6_hdr(skb)->daddr, &ipv6_hdr(skb)->saddr); - if (skb->ip_summed == CHECKSUM_PARTIAL && - (err = skb_checksum_help(skb))) - goto fail; + if (skb->ip_summed == CHECKSUM_PARTIAL) { + if (unlikely(skb_checksum_start_offset(skb) < (int)hlen)) { + err = -EINVAL; + goto fail; + } + err = skb_checksum_help(skb); + if (err) + goto fail; + } prevhdr = skb_network_header(skb) + nexthdr_offset; hroom = LL_RESERVED_SPACE(rt->dst.dev); diff --git a/net/ipv6/netfilter.c b/net/ipv6/netfilter.c index a7025ec87..da7ada12f 100644 --- a/net/ipv6/netfilter.c +++ b/net/ipv6/netfilter.c @@ -144,9 +144,15 @@ int br_ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, frag_id = ipv6_select_ident(net, &ipv6_hdr(skb)->daddr, &ipv6_hdr(skb)->saddr); - if (skb->ip_summed == CHECKSUM_PARTIAL && - (err = skb_checksum_help(skb))) - goto blackhole; + if (skb->ip_summed == CHECKSUM_PARTIAL) { + if (unlikely(skb_checksum_start_offset(skb) < (int)hlen)) { + err = -EINVAL; + goto blackhole; + } + err = skb_checksum_help(skb); + if (err) + goto blackhole; + } prevhdr = skb_network_header(skb) + nexthdr_offset; hroom = LL_RESERVED_SPACE(skb->dev); -- 2.46.0