ID CVE-2020-8834
Summary 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
Vulnerable Configurations
  • cpe:2.3:o:linux:linux_kernel:-:*:*:*:*:*:*:*
    cpe:2.3:o:linux:linux_kernel:-:*:*:*:*:*:*:*
  • cpe:2.3:h:ibm:power8:-:*:*:*:*:*:*:*
    cpe:2.3:h:ibm:power8:-:*:*:*:*:*:*:*
  • cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
    cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
  • cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
    cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
  • cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:*
    cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:*
CVSS
Base: 4.9 (as of 07-10-2022 - 15:43)
Impact:
Exploitability:
CWE CWE-362
CAPEC
  • Leveraging Race Conditions
    The adversary targets a race condition occurring when multiple processes access and manipulate the same resource concurrently, and the outcome of the execution depends on the particular order in which the access takes place. The adversary can leverage a race condition by "running the race", modifying the resource and modifying the normal execution flow. For instance, a race condition can occur while accessing a file: the adversary can trick the system by replacing the original file with his version and cause the system to read the malicious file.
  • Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions
    This attack targets a race condition occurring between the time of check (state) for a resource and the time of use of a resource. A typical example is file access. The adversary can leverage a file access race condition by "running the race", meaning that they would modify the resource between the first time the target program accesses the file and the time the target program uses the file. During that period of time, the adversary could replace or modify the file, causing the application to behave unexpectedly.
Access
VectorComplexityAuthentication
LOCAL LOW NONE
Impact
ConfidentialityIntegrityAvailability
NONE NONE COMPLETE
cvss-vector via4 AV:L/AC:L/Au:N/C:N/I:N/A:C
redhat via4
rpms
  • kernel-0:4.14.0-115.26.1.el7a
  • kernel-abi-whitelists-0:4.14.0-115.26.1.el7a
  • kernel-bootwrapper-0:4.14.0-115.26.1.el7a
  • kernel-debug-0:4.14.0-115.26.1.el7a
  • kernel-debug-debuginfo-0:4.14.0-115.26.1.el7a
  • kernel-debug-devel-0:4.14.0-115.26.1.el7a
  • kernel-debuginfo-0:4.14.0-115.26.1.el7a
  • kernel-debuginfo-common-aarch64-0:4.14.0-115.26.1.el7a
  • kernel-debuginfo-common-ppc64le-0:4.14.0-115.26.1.el7a
  • kernel-debuginfo-common-s390x-0:4.14.0-115.26.1.el7a
  • kernel-devel-0:4.14.0-115.26.1.el7a
  • kernel-doc-0:4.14.0-115.26.1.el7a
  • kernel-headers-0:4.14.0-115.26.1.el7a
  • kernel-kdump-0:4.14.0-115.26.1.el7a
  • kernel-kdump-debuginfo-0:4.14.0-115.26.1.el7a
  • kernel-kdump-devel-0:4.14.0-115.26.1.el7a
  • kernel-tools-0:4.14.0-115.26.1.el7a
  • kernel-tools-debuginfo-0:4.14.0-115.26.1.el7a
  • kernel-tools-libs-0:4.14.0-115.26.1.el7a
  • kernel-tools-libs-devel-0:4.14.0-115.26.1.el7a
  • perf-0:4.14.0-115.26.1.el7a
  • perf-debuginfo-0:4.14.0-115.26.1.el7a
  • python-perf-0:4.14.0-115.26.1.el7a
  • python-perf-debuginfo-0:4.14.0-115.26.1.el7a
refmap via4
misc
suse openSUSE-SU-2020:0543
ubuntu USN-4318-1
Last major update 07-10-2022 - 15:43
Published 09-04-2020 - 22:15
Last modified 07-10-2022 - 15:43
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