Vulnerability identifier: #VU92770
Vulnerability risk: Low
CVSSv3.1: 5.7 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:U/RL:O/RC:C]
CVE-ID:
CWE-ID:
CWE-362
Exploitation vector: Local
Exploit availability: No
Vulnerable software:
Linux kernel
Operating systems & Components /
Operating system
Vendor: Linux Foundation
Description
The vulnerability allows a local user to a crash the entire system.
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 2 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 3 commits, though it is 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')
Mitigation
Install update from vendor's repository.
Vulnerable software versions
Linux kernel:
External links
http://www.openwall.com/lists/oss-security/2020/04/06/2
http://usn.ubuntu.com/usn/usn-4318-1
http://bugs.launchpad.net/ubuntu/+source/linux/+bug/1867717
http://usn.ubuntu.com/4318-1/
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00035.html
Can this vulnerability be exploited remotely?
No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.
Is there known malware, which exploits this vulnerability?
No. We are not aware of malware exploiting this vulnerability.