ipvs: avoid out-of-bounds write in ip_vs_nat_icmp

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "include/net/ip_vs.h",
                        "net/netfilter/ipvs/ip_vs_core.c",
                        "net/netfilter/ipvs/ip_vs_xmit.c"
                    ],
                    "versions": [
                        {
                            "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
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                        },
                        {
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                        {
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                            "status": "affected",
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                        }
                    ]
                }

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "include/net/ip_vs.h",
                        "net/netfilter/ipvs/ip_vs_core.c",
                        "net/netfilter/ipvs/ip_vs_xmit.c"
                    ],
                    "versions": [
                        {
                            "version": "2.6.12",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "2.6.12",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.1.183",
                            "lessThanOrEqual": "6.1.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.6.152",
                            "lessThanOrEqual": "6.6.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.12.104",
                            "lessThanOrEqual": "6.12.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.18.45",
                            "lessThanOrEqual": "6.18.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.1.9",
                            "lessThanOrEqual": "7.1.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.2",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }