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GHSA-J294-CF74-GQ7Q

Vulnerability from github – Published: 2026-10-18 18:32 – Updated: 2026-10-18 18:32

Details

In the Linux kernel, the following vulnerability has been resolved:

KVM: SEV: Nullify "have run CPUs" mask pointer when freeing it

Nullify have_run_cpus when freeing the mask, particularly in the error path of __sev_guest_init(), so that KVM doesn't have to subtly use sev->active to track whether or not the mask has been freed. As pointed out by Sashiko, blindly freeing the mask in sev_vm_destroy() results in a double-free if the mask is freed if __sev_guest_init() fails.

Throw the logic in a helper as nullifying the pointer is frustratingly difficult and weird due to have_run_cpus being a single-entry array when CPUMASK_OFFSTACK=n. Deliberately don't use CPUMASK_VAR_NULL, as it's not directly assignable when the cpumask is on-stack, e.g. requires using a local variable and a memcpy(), which is beyond ridiculous. Furthermore, while clearing the on-stack bitmask is an unnecessary and arguably unwanted side effect, KVM absolutely relies on '0' being the "null" value given that the struct is zero-allocated.

Opportunistically add an alloc() helper to pair with free(); there are just enough call sites to make doing so worthwhile.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98719"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-18T16:17:25Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SEV: Nullify \"have run CPUs\" mask pointer when freeing it\n\nNullify have_run_cpus when freeing the mask, particularly in the error path\nof __sev_guest_init(), so that KVM doesn\u0027t have to subtly use sev-\u003eactive\nto track whether or not the mask has been freed.  As pointed out by Sashiko,\nblindly freeing the mask in sev_vm_destroy() results in a double-free if\nthe mask is freed if __sev_guest_init() fails.\n\nThrow the logic in a helper as nullifying the pointer is frustratingly\ndifficult and weird due to have_run_cpus being a single-entry array when\nCPUMASK_OFFSTACK=n.  Deliberately don\u0027t use CPUMASK_VAR_NULL, as it\u0027s not\ndirectly assignable when the cpumask is on-stack, e.g. requires using a\nlocal variable and a memcpy(), which is beyond ridiculous.  Furthermore,\nwhile clearing the on-stack bitmask is an unnecessary and arguably unwanted\nside effect, KVM absolutely relies on \u00270\u0027 being the \"null\" value given that\nthe struct is zero-allocated.\n\nOpportunistically add an alloc() helper to pair with free(); there are just\nenough call sites to make doing so worthwhile.",
  "id": "GHSA-j294-cf74-gq7q",
  "modified": "2026-10-18T18:32:00Z",
  "published": "2026-10-18T18:32:00Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98719"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0fbc7fec2242de6c3dcea6de55573c428e820173"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8abbc76120a74bfba1851bd97528099d715e45c6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b1de3ebf59507e0edacaa5cfa2225bc1869e1b63"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-98719 (GCVE-0-2026-98719)

Vulnerability from cvelistv5 – Published: 2026-10-18 15:46 – Updated: 2026-10-19 09:24

Title

KVM: SEV: Nullify "have run CPUs" mask pointer when freeing it

Summary

In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Nullify "have run CPUs" mask pointer when freeing it Nullify have_run_cpus when freeing the mask, particularly in the error path of __sev_guest_init(), so that KVM doesn't have to subtly use sev->active to track whether or not the mask has been freed. As pointed out by Sashiko, blindly freeing the mask in sev_vm_destroy() results in a double-free if the mask is freed if __sev_guest_init() fails. Throw the logic in a helper as nullifying the pointer is frustratingly difficult and weird due to have_run_cpus being a single-entry array when CPUMASK_OFFSTACK=n. Deliberately don't use CPUMASK_VAR_NULL, as it's not directly assignable when the cpumask is on-stack, e.g. requires using a local variable and a memcpy(), which is beyond ridiculous. Furthermore, while clearing the on-stack bitmask is an unnecessary and arguably unwanted side effect, KVM absolutely relies on '0' being the "null" value given that the struct is zero-allocated. Opportunistically add an alloc() helper to pair with free(); there are just enough call sites to make doing so worthwhile.

Severity

No CVSS data available.

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 6820 records in the last 180 days details

References

3 references

URL	Tags
https://git.kernel.org/stable/c/b1de3ebf59507e0ed…
https://git.kernel.org/stable/c/0fbc7fec2242de6c3…
https://git.kernel.org/stable/c/8abbc76120a74bfba…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 6aef7cf800098749ff5d660222efaf6e01e98c09 , < b1de3ebf59507e0edacaa5cfa2225bc1869e1b63 (git) Affected: 9784e5ca91b37b387f3f414af4340c54f7a63566 , < 0fbc7fec2242de6c3dcea6de55573c428e820173 (git) Affected: 12c1f6e03f944e399bd2c88441dca5dc702b95a5 , < 8abbc76120a74bfba1851bd97528099d715e45c6 (git)
Linux	Linux	Affected: 6.18.55 , < 6.18.56 (semver) Affected: 7.2.9 , < 7.2.10 (semver)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kvm/svm/sev.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "b1de3ebf59507e0edacaa5cfa2225bc1869e1b63",
              "status": "affected",
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              "versionType": "git"
            },
            {
              "lessThan": "0fbc7fec2242de6c3dcea6de55573c428e820173",
              "status": "affected",
              "version": "9784e5ca91b37b387f3f414af4340c54f7a63566",
              "versionType": "git"
            },
            {
              "lessThan": "8abbc76120a74bfba1851bd97528099d715e45c6",
              "status": "affected",
              "version": "12c1f6e03f944e399bd2c88441dca5dc702b95a5",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kvm/svm/sev.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "6.18.56",
              "status": "affected",
              "version": "6.18.55",
              "versionType": "semver"
            },
            {
              "lessThan": "7.2.10",
              "status": "affected",
              "version": "7.2.9",
              "versionType": "semver"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.56",
                  "versionStartIncluding": "6.18.55",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.10",
                  "versionStartIncluding": "7.2.9",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SEV: Nullify \"have run CPUs\" mask pointer when freeing it\n\nNullify have_run_cpus when freeing the mask, particularly in the error path\nof __sev_guest_init(), so that KVM doesn\u0027t have to subtly use sev-\u003eactive\nto track whether or not the mask has been freed.  As pointed out by Sashiko,\nblindly freeing the mask in sev_vm_destroy() results in a double-free if\nthe mask is freed if __sev_guest_init() fails.\n\nThrow the logic in a helper as nullifying the pointer is frustratingly\ndifficult and weird due to have_run_cpus being a single-entry array when\nCPUMASK_OFFSTACK=n.  Deliberately don\u0027t use CPUMASK_VAR_NULL, as it\u0027s not\ndirectly assignable when the cpumask is on-stack, e.g. requires using a\nlocal variable and a memcpy(), which is beyond ridiculous.  Furthermore,\nwhile clearing the on-stack bitmask is an unnecessary and arguably unwanted\nside effect, KVM absolutely relies on \u00270\u0027 being the \"null\" value given that\nthe struct is zero-allocated.\n\nOpportunistically add an alloc() helper to pair with free(); there are just\nenough call sites to make doing so worthwhile."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:24:30.132Z",
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        "shortName": "Linux"
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        },
        {
          "url": "https://git.kernel.org/stable/c/8abbc76120a74bfba1851bd97528099d715e45c6"
        }
      ],
      "title": "KVM: SEV: Nullify \"have run CPUs\" mask pointer when freeing it",
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        "engine": "bippy-1.2.0"
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98719",
    "datePublished": "2026-10-18T15:46:54.631Z",
    "dateReserved": "2026-09-25T10:25:14.366Z",
    "dateUpdated": "2026-10-19T09:24:30.132Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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