Vulnerability · Published Apr 9, 2020 · Assigned by canonical
CVE-2020-8834Linux kernel KVM Power8 conflicting use of HSTATE_HOST_R1
Medium 6.5
In plain English
A medium-severity security flaw in Linux kernel from Linux kernel. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | linux | 4.18.6-1 | DEBIAN-CVE-2020-8834 |
| Debian:13 | linux | 4.18.6-1 | DEBIAN-CVE-2020-8834 |
| Debian:14 | linux | 4.18.6-1 | DEBIAN-CVE-2020-8834 |
| Ubuntu:22.04:LTS | linux-intel-iot-realtime | no fix listed | UBUNTU-CVE-2020-8834 |
| Ubuntu:24.04:LTS | linux-raspi-realtime | no fix listed | UBUNTU-CVE-2020-8834 |
| Ubuntu:22.04:LTS | linux-realtime | no fix listed | UBUNTU-CVE-2020-8834 |
| Ubuntu:22.04:LTS | linux-riscv | no fix listed | UBUNTU-CVE-2020-8834 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Linux kernel | Linux kernel | 4.8 – before unspecifiedunspecified – before 4.18 |
Weakness: CWE-368 · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
References
- https://www.openwall.com/lists/oss-security/2020/04/06/2 x_refsource_MISC
- https://usn.ubuntu.com/usn/usn-4318-1 x_refsource_MISC
- https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1867717 x_refsource_MISC
- USN-4318-1 vendor-advisory, x_refsource_UBUNTU
- openSUSE-SU-2020:0543 vendor-advisory, x_refsource_SUSE