From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794063720; b=RUvL9VThbvdQb71/uk8vG9bCrbtPNUIUS31HRN8MQACxz3bTq/HzGuOhKjwzeewccCQ5 yY0VSxB2tvDkVguTCS1dw6vt/3sIA8UkxQdgJB1QsdVX7Ej/+N+cHMAKQFA60VCMU8F5b 3zUuhlyq/LXbXOT4+emYl6OjPVdkatHfZ5ymAi24sj/rTOgDQ3TGw9HndFrk12sZ9eKN0 VMh7hyh8h6kzU/3PY+zEBxXHkeegE53FKdUJiUPre+hYOMpnEIBHCRExYcsrMdM3TP5sN UeIrNKmEmP5Ekf4ZvCWRIYjyxQcPo92vi1wKVw4L4DX0rvc1zO6S/Vrah3KRN2zVTtA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794063720; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=LumB+2YTncyGttT/zv6Boqk+IXTiymlr4yvTiMRt+bo=; b=gFtvtTk0oM4b5+Xcf3VZ2m52TI1ZPneTyXZm/PQKQLDuSV4n2zLB1bx3Vz6w/VAUX5aV dy80xEcWJ2INwOFQNJQctu7wJrSr6nUgtOSKp+5tGyPcOCIfB0IAyL97prGMt0ExZfF5Y gy9+nKpDeodgRf3dp4is7fEkZjVrs9naOy6cVZRfDeGPa7W2EbMVKIq7qmZdNv9McfiAm EbT5widuFxsyLuwz1n+O5AfVs9HPJSsFE+T5sHz0qR9or/J2kiP9JP1Tp4ukifFukXOah Jq2ot0jHCJ5eVIsYZ9YHP/GBoy1S+Bnj8jBL4Coj5H9f8dpdgPUZiZA1CBUYBKG4cfw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=DIdsVzVh; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3BCA1606D83F; Sat, 7 Nov 2026 15:02:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=DIdsVzVh Received: by smtp.kernel.org (Postfix) with ESMTPSA id D96A91F0089F; Sat, 7 Nov 2026 15:01:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794063720; bh=LumB+2YTncyGttT/zv6Boqk+IXTiymlr4yvTiMRt+bo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=DIdsVzVhlw7HbCmDjBMyrsmHsZtsnIaNMZS+eroPO9FNGA3O54eXvTJhK9abofEuY 2bpJQKHzXjCep/pAVyfBl0rMKM5FeteLzz8a2ni0TOGbPcOB/O1Pezv2iyqBjJgsOB onCjOB/7OQCqi0e9dFPYg57UP7idMhBc6Vgpi4Ss= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Willem de Bruijn , Kamil Sawicki , Kuniyuki Iwashima , Eric Dumazet , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.18 820/869] net: limit priority VLAN untag depth Date: Sat, 7 Nov 2026 08:58:22 -0500 Message-ID: <20261107134920.790500352@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261107134852.069646174@linuxfoundation.org> References: <20261107134852.069646174@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kamil Sawicki [ Upstream commit d3ff07f5acc573e5f72bf1c581bae5d05191ba61 ] The priority VLAN receive path can repeatedly remove VID 0 tags and retry packet processing. Unlike the read-only VLAN protocol parser, this path has no limit on the number of nested tags it consumes. Each skb_vlan_untag() advances skb->data and resets header offsets. The offsets are stored in 16-bit fields. With enough nested tags, the network or transport offset can wrap. A later protocol handler can then derive a large pull length from the wrapped offsets and access memory outside the skb allocation. Apply the existing VLAN_MAX_DEPTH limit to the exceptional VID 0 retry. Count the tag already stored in skb VLAN metadata as the first level, then stop before untagging a ninth level. Keep the accounting inside this uncommon branch so the regular VLAN receive path is unaffected. A single VID 0 priority tag before a real VLAN tag is valid. No normal deployment was found that intentionally emits multiple consecutive VID 0 tags; permitting eight levels is therefore conservative. The issue was found while researching the Linux network receive path for Google kvmCTF, with OpenAI Codex (gpt-5.6-sol) assisting the analysis. The affected path, reproducer and fix were manually reviewed and tested. Fixes: 36b2f61a42c2 ("net: handle 802.1P vlan 0 packets properly") Cc: stable@vger.kernel.org Reviewed-by: Willem de Bruijn Signed-off-by: Kamil Sawicki Reviewed-by: Kuniyuki Iwashima Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20261024004835.17862-1-user148783812897@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/core/dev.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/net/core/dev.c b/net/core/dev.c index 0bfd5e9940df0..673223065b955 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6074,6 +6074,8 @@ static int __netif_receive_skb_core(struct sk_buff **pskb, bool pfmemalloc, } if (unlikely(skb_vlan_tag_present(skb)) && !netdev_uses_dsa(skb->dev)) { + unsigned int priority_tag_depth = 1; + check_vlan_id: if (skb_vlan_tag_get_id(skb)) { /* Vlan id is non 0 and vlan_do_receive() above couldn't @@ -6085,6 +6087,12 @@ static int __netif_receive_skb_core(struct sk_buff **pskb, bool pfmemalloc, * 802.1Q or 802.1AD and vlan_do_receive() above could * not find vlan dev for vlan id 0. */ + if (unlikely(priority_tag_depth >= VLAN_MAX_DEPTH)) { + drop_reason = SKB_DROP_REASON_RECURSION_LIMIT; + goto drop; + } + + priority_tag_depth++; __vlan_hwaccel_clear_tag(skb); skb = skb_vlan_untag(skb); if (unlikely(!skb)) -- 2.53.0