ghsa-jx29-mm4x-qpqh
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
KVM: SVM: WARN on vNMI + NMI window iff NMIs are outright masked
When requesting an NMI window, WARN on vNMI support being enabled if and only if NMIs are actually masked, i.e. if the vCPU is already handling an NMI. KVM's ABI for NMIs that arrive simultanesouly (from KVM's point of view) is to inject one NMI and pend the other. When using vNMI, KVM pends the second NMI simply by setting V_NMI_PENDING, and lets the CPU do the rest (hardware automatically sets V_NMI_BLOCKING when an NMI is injected).
However, if KVM can't immediately inject an NMI, e.g. because the vCPU is in an STI shadow or is running with GIF=0, then KVM will request an NMI window and trigger the WARN (but still function correctly).
Whether or not the GIF=0 case makes sense is debatable, as the intent of KVM's behavior is to provide functionality that is as close to real hardware as possible. E.g. if two NMIs are sent in quick succession, the probability of both NMIs arriving in an STI shadow is infinitesimally low on real hardware, but significantly larger in a virtual environment, e.g. if the vCPU is preempted in the STI shadow. For GIF=0, the argument isn't as clear cut, because the window where two NMIs can collide is much larger in bare metal (though still small).
That said, KVM should not have divergent behavior for the GIF=0 case based on whether or not vNMI support is enabled. And KVM has allowed simultaneous NMIs with GIF=0 for over a decade, since commit 7460fb4a3400 ("KVM: Fix simultaneous NMIs"). I.e. KVM's GIF=0 handling shouldn't be modified without a really good reason to do so, and if KVM's behavior were to be modified, it should be done irrespective of vNMI support.
{
"affected": [],
"aliases": [
"CVE-2024-39483"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-07-05T07:15:10Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SVM: WARN on vNMI + NMI window iff NMIs are outright masked\n\nWhen requesting an NMI window, WARN on vNMI support being enabled if and\nonly if NMIs are actually masked, i.e. if the vCPU is already handling an\nNMI. KVM\u0027s ABI for NMIs that arrive simultanesouly (from KVM\u0027s point of\nview) is to inject one NMI and pend the other. When using vNMI, KVM pends\nthe second NMI simply by setting V_NMI_PENDING, and lets the CPU do the\nrest (hardware automatically sets V_NMI_BLOCKING when an NMI is injected).\n\nHowever, if KVM can\u0027t immediately inject an NMI, e.g. because the vCPU is\nin an STI shadow or is running with GIF=0, then KVM will request an NMI\nwindow and trigger the WARN (but still function correctly).\n\nWhether or not the GIF=0 case makes sense is debatable, as the intent of\nKVM\u0027s behavior is to provide functionality that is as close to real\nhardware as possible. E.g. if two NMIs are sent in quick succession, the\nprobability of both NMIs arriving in an STI shadow is infinitesimally low\non real hardware, but significantly larger in a virtual environment, e.g.\nif the vCPU is preempted in the STI shadow. For GIF=0, the argument isn\u0027t\nas clear cut, because the window where two NMIs can collide is much larger\nin bare metal (though still small).\n\nThat said, KVM should not have divergent behavior for the GIF=0 case based\non whether or not vNMI support is enabled. And KVM has allowed\nsimultaneous NMIs with GIF=0 for over a decade, since commit 7460fb4a3400\n(\"KVM: Fix simultaneous NMIs\"). I.e. KVM\u0027s GIF=0 handling shouldn\u0027t be\nmodified without a *really* good reason to do so, and if KVM\u0027s behavior\nwere to be modified, it should be done irrespective of vNMI support.",
"id": "GHSA-jx29-mm4x-qpqh",
"modified": "2024-07-08T18:31:16Z",
"published": "2024-07-05T09:33:44Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-39483"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1d87cf2eba46deaff6142366127f2323de9f84d1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b4bd556467477420ee3a91fbcba73c579669edc6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f79edaf7370986d73d204b36c50cc563a4c0f356"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.