CVE-2020-8834: Linux kernel KVM Power8 conflicting use of HSTATE_HOST_R1
First published: Wed Apr 01 2020(Updated: )
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.
Credit: security@ubuntu.com security@ubuntu.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| redhat/kernel-alt | <0:4.14.0-115.26.1.el7a | 0:4.14.0-115.26.1.el7a |
| Linux Linux kernel | ||
| Ibm Power8 | ||
| Canonical Ubuntu Linux | =16.04 | |
| Canonical Ubuntu Linux | =18.04 | |
| openSUSE Leap | =15.1 | |
| redhat/Linux | <4.18 | 4.18 |
| All of | ||
| Linux Linux kernel | ||
| Ibm Power8 | ||
| debian/linux | 5.10.223-1 5.10.226-1 6.1.115-1 6.1.119-1 6.11.10-1 6.12.5-1 |
Remedy
Apply the following three Linux kernel commits, though possibly only the first commit is strictly necessary: 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")
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Reference Links
- https://www.cve.org/CVERecord?id=CVE-2020-8834 https://nvd.nist.gov/vuln/detail/CVE-2020-8834 https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1867717 https://www.openwall.com/lists/oss-security/2020/04/06/2
- https://bugzilla.redhat.com/show_bug.cgi?id=1819615
- https://access.redhat.com/errata/RHSA-2020:2854
- https://access.redhat.com/security/cve/cve-2020-8834
- 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
- https://launchpad.net/bugs/cve/CVE-2020-8834
- https://git.kernel.org/linus/6f597c6b63b6f3675914b5ec8fcd008a58678650
- https://git.kernel.org/linus/009c872a8bc4d38f487a9bd62423d019e4322517
- https://git.kernel.org/linus/7b0e827c6970e8ca77c60ae87592204c39e41245
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=1821909
- https://security-tracker.debian.org/tracker/CVE-2020-8834
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-8834
- https://nvd.nist.gov/vuln/detail/CVE-2020-8834
- https://ubuntu.com/security/CVE-2020-8834
Frequently Asked Questions
What is CVE-2020-8834?
CVE-2020-8834 is a vulnerability in the Linux kernel on Power8 processors that allows an attacker with code execution in a guest VM to cause stack corruption in the host kernel.
What is the severity of CVE-2020-8834?
CVE-2020-8834 has a severity rating of high.
Which software is affected by CVE-2020-8834?
CVE-2020-8834 affects Linux kernel versions 4.15.0-96.97 and 4.18~.
How can I fix CVE-2020-8834?
To fix CVE-2020-8834, update your Linux kernel to version 4.15.0-96.97 or 4.18~.
Where can I find more information about CVE-2020-8834?
You can find more information about CVE-2020-8834 on the Ubuntu Security Notice (USN) page and the Openwall mailing list.
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