CVE-2026-80901

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CVE-2026-80901

Summary: ipvs: fix the checksum validations

Details: In the Linux kernel, the following vulnerability has been resolved: ipvs: fix the checksum validations ip_vs_in_icmp_v6() is missing checksum validation for ICMPv6 packets from clients. In fact, as for TCP/UDP we should validate the checksum for ICMP packets only when we mangle the packets on MASQ or on reply for tunnel. Also, Sashiko points out that handle_response_icmp() being common for IPv4 and IPv6 is missing the pseudo-header calculation while validating ICMPv6 messages from real servers which is a problem if checksum is not validated by the hardware. Fix the problems by creating ip_vs_checksum_common_check() helper and use it for TCP/UDP/ICMP both for IPv4 and IPv6. Rely on the nf_checksum() for validating the ICMP messages but use it also for TCP and UDP. Use correct IP offset for IP_VS_DBG_RL_PKT for TCP/UDP/SCTP. IPVS packets (TCP/UDP/SCTP/ICMP) do not need checksum validation on LOCAL_OUT (local clients or local real servers) and on FORWARD (traffic from servers on LAN). Do it only on LOCAL_IN, in case nf_checksum() is not called on PRE_ROUTING. Also, ip_vs_checksum_complete() can be marked static.

References: https://git.kernel.org/stable/c/00eb23829fd08df1b5e057cb6b625996a70e7e65, https://git.kernel.org/stable/c/5558a85add073215b298f3e044ff9a6d86d714ae, https://git.kernel.org/stable/c/9cbe2c0fdb71904ee929b1851cdc1c73341a03c0, https://git.kernel.org/stable/c/b3869d9b54e76dff64118dee4c8fd9302fcd5171, https://git.kernel.org/stable/c/d418d73acf8be62744dc47359dfdde8c2148845d, https://git.kernel.org/stable/c/e876b75b9020a97bbdc79721e7fc749024891c65, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80901.json, https://nvd.nist.gov/vuln/detail/CVE-2026-80901, https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git