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

Vulnerability from cvelistv5 – Published: 2026-10-18 15:46 – Updated: 2026-10-19 09:24
VLAI
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 6637 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 6aef7cf800098749ff5d660222efaf6e01e98c09 , < b1de3ebf59507e0edacaa5cfa2225bc1869e1b63 (git)
Affected: 9784e5ca91b37b387f3f414af4340c54f7a63566 , < 0fbc7fec2242de6c3dcea6de55573c428e820173 (git)
Affected: 12c1f6e03f944e399bd2c88441dca5dc702b95a5 , < 8abbc76120a74bfba1851bd97528099d715e45c6 (git)
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Linux Linux Affected: 6.18.55 , < 6.18.56 (semver)
Affected: 7.2.9 , < 7.2.10 (semver)
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{
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          "programFiles": [
            "arch/x86/kvm/svm/sev.c"
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          "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": {
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        "shortName": "Linux"
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    "datePublished": "2026-10-18T15:46:54.631Z",
    "dateReserved": "2026-09-25T10:25:14.366Z",
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            "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."
          }
        ],
        "id": "CVE-2026-98719",
        "lastModified": "2026-10-19T10:19:36.137",
        "metrics": {},
        "published": "2026-10-18T16:17:25.463",
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      "cve": "CVE-2026-98719",
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      "product_status:known_affected": "161",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: KVM: SEV: Nullify \"have run CPUs\" mask pointer when freeing it",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98719.json",
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      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2026/cve-2026-98719.json",
      "version": "4"
    }
  }
}



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