CVE-2020-8834
Description
A flaw was found in the way the KVM hypervisor on the Power8 processor stores the r1 register state in the 'HSTATE_HOST_R1' field on the Linux kernel stack. This flaw occurs while handling hypercalls in Transactional Memory (TM) suspend mode in the kvmppc_save_tm and kvmppc_restore_tm routines, leading to host stack corruption. R1 register holds a stack frame address and its corruption leads the kernel into panic state. A guest user can use this flaw to crash the host kernel, resulting in a denial of service.
Statement
This issue does not affect the versions of the Linux kernel as shipped with the Red Hat Enterprise Linux 5, 6, 8 and Red Hat Enterprise MRG 2. This issue affects the versions of the kernel package as shipped with the Red Hat Enterprise Linux 7. Future kernel updates for the Red Hat Enterprise Linux 7 may address this issue.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6 | 6.5 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | High | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Changed | Changed | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: Modify Memory; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.
Integrity,Confidentiality,Availability,Access Control
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands; Bypass Protection Mechanism
Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy.
Integrity,Confidentiality,Availability,Access Control,Other
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Other
When the consequence is arbitrary code execution, this can often be used to subvert any other security service.
Acknowledgements
Red Hat would like to thank Gustavo Romero and Paul Mackerras for reporting this issue.
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