CVE-2020-8834

MEDIUM

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")

References

http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00035.html

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1867717

https://usn.ubuntu.com/4318-1/

https://usn.ubuntu.com/usn/usn-4318-1

https://www.openwall.com/lists/oss-security/2020/04/06/2

Details

Source: MITRE

Published: 2020-04-09

Updated: 2020-04-23

Type: CWE-362

Risk Information

CVSS v2.0

Base Score: 4.9

Vector: AV:L/AC:L/Au:N/C:N/I:N/A:C

Impact Score: 6.9

Exploitability Score: 3.9

Severity: MEDIUM

CVSS v3.0

Base Score: 6.5

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

Impact Score: 4

Exploitability Score: 2

Severity: MEDIUM

Tenable Plugins

View all (10 total)

IDNameProductFamilySeverity
143086RHEL 7 : kernel-alt (RHSA-2020:2854)NessusRed Hat Local Security Checks
high
138272SUSE SLES15 Security Update : kernel (SUSE-SU-2020:1663-1)NessusSuSE Local Security Checks
critical
136168SUSE SLED15 / SLES15 Security Update : kernel (SUSE-SU-2020:1146-1)NessusSuSE Local Security Checks
medium
136166SUSE SLES12 Security Update : kernel (SUSE-SU-2020:1142-1)NessusSuSE Local Security Checks
high
136165SUSE SLES12 Security Update : kernel (SUSE-SU-2020:1141-1)NessusSuSE Local Security Checks
medium
136075SUSE SLED15 / SLES15 Security Update : kernel (SUSE-SU-2020:1123-1)NessusSuSE Local Security Checks
medium
136026SUSE SLES12 Security Update : kernel (SUSE-SU-2020:1119-1)NessusSuSE Local Security Checks
medium
136025SUSE SLES12 Security Update : kernel (SUSE-SU-2020:1118-1)NessusSuSE Local Security Checks
high
136006openSUSE Security Update : the Linux Kernel (openSUSE-2020-543)NessusSuSE Local Security Checks
medium
135269Ubuntu 16.04 LTS / 18.04 LTS : linux, linux-hwe vulnerabilities (USN-4318-1)NessusUbuntu Local Security Checks
low