CVE-2024-39483 Affecting kernel-rt package, versions <0:5.14.0-427.40.1.el9_4
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published25 Oct 2024
- disclosed16 Oct 2024
Introduced: 16 Oct 2024
CVE-2024-39483 (opens in a new tab)How to fix?
Upgrade AlmaLinux:9 kernel-rt to version 0:5.14.0-427.40.1.el9_4 or higher.
This issue was patched in ALSA-2024:8162.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-rt package and not the kernel-rt package as distributed by AlmaLinux.
See How to fix? for AlmaLinux:9 relevant fixed versions and status.
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.
References
- https://errata.almalinux.org/9/ALSA-2024-8162.html
- https://access.redhat.com/security/cve/CVE-2024-39483
- https://access.redhat.com/errata/RHSA-2024:8162
- https://git.kernel.org/stable/c/1d87cf2eba46deaff6142366127f2323de9f84d1
- https://git.kernel.org/stable/c/b4bd556467477420ee3a91fbcba73c579669edc6
- https://git.kernel.org/stable/c/f79edaf7370986d73d204b36c50cc563a4c0f356