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CVE-2020-8834

Linux kernel KVM Power8 conflicting use of HSTATE_HOST_R1

MEDIUM
6.5
CVSS Score
Published: April 9, 2020 at 10:10 PM UTC
Updated: June 17, 2026 at 03:27 AM UTC
4 products affected across 4 vendorsLinux KernelUbuntu LinuxLeap· also runs on 1 platform

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Severity
MEDIUM6.5
Exploit prediction
EPSS 0.3%

Description

KVM in the Linux kernel on Power8 processors has a conflicting use of HSTATE_HOST_R1 to store r1 state in kvmppc_hv_entry plus in kvmppc_{save,restore}_tm, leading to a stack corruption. Because of this, an attacker with the ability run code in kernel space of a guest VM can cause the host kernel to panic. There were two commits that, according to the reporter, introduced the vulnerability: f024ee098476 ("KVM: PPC: Book3S HV: Pull out TM state save/restore into separate procedures") 87a11bb6a7f7 ("KVM: PPC: Book3S HV: Work around XER[SO] bug in fake suspend mode") The former landed in 4.8, the latter in 4.17. This was fixed without realizing the impact in 4.18 with the following three commits, though it's believed the first is the only strictly necessary commit: 6f597c6b63b6 ("KVM: PPC: Book3S PR: Add guest MSR parameter for kvmppc_save_tm()/kvmppc_restore_tm()") 7b0e827c6970 ("KVM: PPC: Book3S HV: Factor fake-suspend handling out of kvmppc_save/restore_tm") 009c872a8bc4 ("KVM: PPC: Book3S PR: Move kvmppc_save_tm/kvmppc_restore_tm to separate file")

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Ubuntu Linux· Canonicalrubygems
95%
16.0418.04
Linux Kernel· Linux
95%
All versions
ibm-power8 (environment)
Leap· openSUSEdrupal
95%
15.1
Linux Kernel· Linux Kernel
60%
v ≥ 4.8v < 4.184.8
Affected range stops below 4.18, so it looks safe — our inference, not a vendor statement

Runs on — not affected

The affected product only carries this flaw when running on these platforms. The platforms themselves are not vulnerable.

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (5)

Vendor Advisoryx_refsource_SUSEMailing ListThird Party Advisory
Source: [email protected]
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00035.html
x_refsource_MISCExploitThird Party Advisory
Source: [email protected]
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1867717
Vendor Advisoryx_refsource_UBUNTUThird Party Advisory
Source: [email protected]
https://usn.ubuntu.com/4318-1/
x_refsource_MISCThird Party Advisory
Source: [email protected]
https://usn.ubuntu.com/usn/usn-4318-1
x_refsource_MISCMailing ListThird Party Advisory
Source: [email protected]
https://www.openwall.com/lists/oss-security/2020/04/06/2

CVSS

6.5MEDIUMcanonical
Attack Vector
LOCAL
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-368CWE-362

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