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CVE-2020-8834

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Date: April 23, 2020

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")

Language: C

Severity Score

Severity Score

Weakness Type (CWE)

Race Conditions

CWE-362

Top Fix

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CVSS v3.1

Base Score:
Attack Vector (AV): LOCAL
Attack Complexity (AC): LOW
Privileges Required (PR): LOW
User Interaction (UI): NONE
Scope (S): CHANGED
Confidentiality (C): NONE
Integrity (I): NONE
Availability (A): HIGH

CVSS v2

Base Score:
Access Vector (AV): LOCAL
Access Complexity (AC): LOW
Authentication (AU): NONE
Confidentiality (C): NONE
Integrity (I): NONE
Availability (A): COMPLETE
Additional information:

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