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 0D3E63D3002 for ; Fri, 28 Aug 2026 06:49:38 +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=1787899780; cv=none; b=f17LMNTAAt3KbfKsXuqTkFrIyFscp68imqjc7HGiMAl6XH4tdIiTJlN5uSCABPmTqtIHsZRq+jGBkmEURJqTddQinvxKCTnnm0lC5JPIq+C7DZFO4KxIEb/Z2QBqpAUEsshRy9Ixq7KZ5oqstWhGx3N5svnDVGLpVYMKU46zqZ4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787899780; c=relaxed/simple; bh=7yd1bi8DGagiOpKhqqHlNvKXorCa37BEG6wmz+WKI8k=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=PFoUk4eJrZVH3yYirzd7DO5Kz1qjneLOgeOh47vulRNMT9R5nfoypEy2ctQ9B0smp4SR/OtS+COfg3+mfek+ERNCFxCIU/cPkY23ctaH/rsrO2jj66TUyelx/+baK6h7zVnwFqcxcSWZZSFQeF114DV2Tx4kFeY/0hrVVXZp/CM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=1mADljQl; 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="1mADljQl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 11FC81F000E9; Fri, 28 Aug 2026 06:49:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787899778; bh=tM93Nq2f+aJ52PNhpJ4Xp/JSHOhHJ1kxxsm38/77qJA=; h=From:To:Cc:Subject:Date:Reply-To; b=1mADljQla6zRYbTFGn9WB731hBNbLW4LYYUj2p0sOMIKpZD8u/KLYGh4qfq8oky1y kxxddHDQv3B8g0heglplnYWjRI+CiCdYdPuXDZQeXZj065lV0iVuzebNJ0ULrSWCDZ bkRWJ6Ov27+xjEBI6KsAgRBkL/kQUeuWIQF4KCLs= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-80612: net: lwtunnel: Drop skb metadata before LWT encapsulation Date: Fri, 28 Aug 2026 08:48:49 +0200 Message-ID: <2026082834-CVE-2026-80612-cedf@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4799; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=Li0c5mk0nWOlMrJKNOyapd1em8EKPkPak4DjKcyECmc=; b=owGbwMvMwCRo6H6F97bub03G02pJDFkT9Z00Nh7uPyT4ibnh8zSxrI8iMbtfhTSzpRy9HVUzb 57uE/6bHbEsDIJMDLJiiixftvEc3V9xSNHL0PY0zBxWJpAhDFycAnCT2xnmSntf7FO6HPVmn3+X bOOtq3EzFmyrYJgrEL3Nv7SJf/9p1nMnTnBXluzyzPgPAA== X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: net: lwtunnel: Drop skb metadata before LWT encapsulation skb metadata is meant for passing information between XDP and TC. It lives in the skb headroom, immediately before skb->data. LWT programs cannot access the __sk_buff->data_meta pseudo-pointer to metadata. However, LWT encapsulation prepends outer headers, moving skb->data back over the headroom where the metadata sits. On an RX-originated (forwarded) packet that still carries XDP metadata this goes wrong in two different ways, depending on the encap type: 1. Non-BPF LWT encaps (mpls, seg6, ioam6 ...) call skb_push()/skb_pull() and silently overwrite the metadata that sits in the headroom. 2) BPF LWT xmit calls bpf_skb_change_head(), which uses skb_data_move(). That helper expects metadata immediately before skb->data. But since the IP output path runs LWT xmit before neighbour output has built the outgoing L2 header, for forwarded packets skb->data points at the L3 header while skb_mac_header() still points at the old L2 header. skb_data_move() sees metadata ending at skb_mac_header(), not before skb->data, warns and clears metadata: WARNING: CPU: 21 PID: 454557 at include/linux/skbuff.h:4609 skb_data_move+0x47/0x90 CPU: 21 UID: 0 PID: 454557 Comm: napi/iconduit-g Tainted: G O 6.18.21 #1 RIP: 0010:skb_data_move+0x47/0x90 Call Trace: bpf_skb_change_head+0xe6/0x1a0 bpf_prog_...+0x213/0x2e3 run_lwt_bpf.isra.0+0x1d3/0x360 bpf_xmit+0x46/0xe0 lwtunnel_xmit+0xa1/0xf0 ip_finish_output2+0x1e7/0x5e0 ip_output+0x63/0x100 __netif_receive_skb_one_core+0x85/0xa0 process_backlog+0x9c/0x150 __napi_poll+0x2b/0x190 net_rx_action+0x40b/0x7f0 handle_softirqs+0xd2/0x270 do_softirq+0x3f/0x60 That is what happens, as for how to fix it - a received packet that carries metadata can reach an encap through any of the three LWT redirect modes: LWTUNNEL_STATE_INPUT_REDIRECT ip6_rcv_finish dst_input lwtunnel_input LWTUNNEL_STATE_OUTPUT_REDIRECT ip6_rcv_finish dst_input ip6_forward ip6_forward_finish dst_output lwtunnel_output LWTUNNEL_STATE_XMIT_REDIRECT ip6_rcv_finish dst_input ip6_forward ip6_forward_finish dst_output ip6_output ip6_finish_output ip6_finish_output2 lwtunnel_xmit Every encap funnels through the three LWT dispatch helpers, so drop the metadata there, right before handing the skb to the encap op. This single chokepoint covers all encap types and all three redirect modes: - lwtunnel_input(): seg6, rpl, ila, seg6_local - lwtunnel_output(): ioam6 - lwtunnel_xmit(): mpls, LWT BPF xmit Alternatively, we could clear the metadata right after TC ingress hook. That would require a compromise, however. Metadata would become inaccessible from TC egress (in setups where it actually reaches the hook it tact, that is without any L2 tunnels on path). The Linux kernel CVE team has assigned CVE-2026-80612 to this issue. Affected and fixed versions =========================== Issue introduced in 6.19 with commit 8989d328dfe7c7a3b9f4b9f0ef60006d277f81cc and fixed in 7.1.5 with commit 19eec11f3ab5dd29ba58f5f209c24e946c95ef12 Issue introduced in 6.19 with commit 8989d328dfe7c7a3b9f4b9f0ef60006d277f81cc and fixed in 7.2 with commit c00320b0e355c4bf0ae4743a53b4180fea237546 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-80612 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: net/core/lwtunnel.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/19eec11f3ab5dd29ba58f5f209c24e946c95ef12 https://git.kernel.org/stable/c/c00320b0e355c4bf0ae4743a53b4180fea237546