high
8.8
CWE
862
Advisory Published
CVE Published
CVE Published
Updated

CVE-2021-3656

First published: Tue Jul 20 2021(Updated: )

A flaw was found in the KVM's AMD code for supporting SVM nested virtualization. The flaw occurs when processing the VMCB (virtual machine control block) provided by the L1 guest to spawn/handle a nested guest (L2). Due to improper validation of the "virt_ext" field, this issue could allow a malicious L1 to disable both VMLOAD/VMSAVE intercepts and VLS (Virtual VMLOAD/VMSAVE) for the L2 guest. As a result, the L2 guest would be allowed to read/write physical pages of the host, resulting in a crash of the entire system, leak of sensitive data or potential guest-to-host escape.

Credit: secalert@redhat.com secalert@redhat.com

Affected SoftwareAffected VersionHow to fix
redhat/kernel-rt<0:3.10.0-1160.45.1.rt56.1185.el7
0:3.10.0-1160.45.1.rt56.1185.el7
redhat/kernel<0:3.10.0-1160.45.1.el7
0:3.10.0-1160.45.1.el7
redhat/kernel<0:3.10.0-957.84.1.el7
0:3.10.0-957.84.1.el7
redhat/kernel<0:3.10.0-1062.59.1.el7
0:3.10.0-1062.59.1.el7
redhat/kernel-rt<0:4.18.0-305.25.1.rt7.97.el8_4
0:4.18.0-305.25.1.rt7.97.el8_4
redhat/kernel<0:4.18.0-305.25.1.el8_4
0:4.18.0-305.25.1.el8_4
redhat/kernel<0:4.18.0-147.56.1.el8_1
0:4.18.0-147.56.1.el8_1
redhat/kernel-rt<0:4.18.0-193.68.1.rt13.118.el8_2
0:4.18.0-193.68.1.rt13.118.el8_2
redhat/kernel<0:4.18.0-193.68.1.el8_2
0:4.18.0-193.68.1.el8_2
Linux Linux kernel>=4.13<4.14.245
Linux Linux kernel>=4.15<4.19.205
Linux Linux kernel>=4.20<5.4.142
Linux Linux kernel>=5.5<5.10.60
Linux Linux kernel>=5.11<5.13.12
Linux Linux kernel=5.14
Linux Linux kernel=5.14-rc1
Linux Linux kernel=5.14-rc2
Linux Linux kernel=5.14-rc3
Linux Linux kernel=5.14-rc4
Linux Linux kernel=5.14-rc5
Linux Linux kernel=5.14-rc6
Fedoraproject Fedora=33
Fedoraproject Fedora=34
Redhat Software Collections
Redhat Enterprise Linux Server=7.0
Redhat Openstack=13
Redhat Enterprise Linux=8.0
Redhat Enterprise Linux Desktop=7.0
Redhat Enterprise Linux Eus=8.1
Redhat Enterprise Linux Eus=8.2
Redhat Enterprise Linux Eus=8.4
Redhat Enterprise Linux For Ibm Z Systems=7.0
Redhat Enterprise Linux For Ibm Z Systems=8.0
Redhat Enterprise Linux For Ibm Z Systems Eus=8.1
Redhat Enterprise Linux For Ibm Z Systems Eus=8.2
Redhat Enterprise Linux For Ibm Z Systems Eus=8.4
Redhat Enterprise Linux For Power Big Endian=7.0
Redhat Enterprise Linux For Power Little Endian=7.0
Redhat Enterprise Linux For Power Little Endian=8.0
Redhat Enterprise Linux For Power Little Endian Eus=8.1
Redhat Enterprise Linux For Power Little Endian Eus=8.2
Redhat Enterprise Linux For Power Little Endian Eus=8.4
Redhat Enterprise Linux For Real Time=7
Redhat Enterprise Linux For Real Time=8
Redhat Enterprise Linux For Real Time For Nfv=7
Redhat Enterprise Linux For Real Time For Nfv=8
Redhat Enterprise Linux For Real Time For Nfv Tus=8.2
Redhat Enterprise Linux For Real Time For Nfv Tus=8.4
Redhat Enterprise Linux For Real Time Tus=8.2
Redhat Enterprise Linux For Real Time Tus=8.4
Redhat Enterprise Linux For Scientific Computing=7.0
Redhat Enterprise Linux Server=7.0
Redhat Enterprise Linux Server Aus=7.6
Redhat Enterprise Linux Server Aus=7.7
Redhat Enterprise Linux Server Aus=8.2
Redhat Enterprise Linux Server Aus=8.4
Redhat Enterprise Linux Server For Power Little Endian Update Services For Sap Solutions=7.6
Redhat Enterprise Linux Server For Power Little Endian Update Services For Sap Solutions=8.1
Redhat Enterprise Linux Server For Power Little Endian Update Services For Sap Solutions=8.2
Redhat Enterprise Linux Server For Power Little Endian Update Services For Sap Solutions=8.4
Redhat Enterprise Linux Server Tus=7.6
Redhat Enterprise Linux Server Tus=7.7
Redhat Enterprise Linux Server Tus=8.2
Redhat Enterprise Linux Server Tus=8.4
Redhat Enterprise Linux Server Update Services For Sap Solutions=7.6
Redhat Enterprise Linux Server Update Services For Sap Solutions=7.7
Redhat Enterprise Linux Server Update Services For Sap Solutions=8.1
Redhat Enterprise Linux Server Update Services For Sap Solutions=8.2
Redhat Enterprise Linux Server Update Services For Sap Solutions=8.4
Redhat Enterprise Linux Workstation=7.0
Redhat 3scale Api Management=2.0
Redhat Enterprise Linux=7.0
Redhat Enterprise Linux=8.0
Redhat Codeready Linux Builder
Redhat Enterprise Linux Eus=8.1
Redhat Enterprise Linux Eus=8.2
Redhat Enterprise Linux Eus=8.4
Redhat Enterprise Linux For Power Little Endian=8.0
Redhat Enterprise Linux For Power Little Endian Eus=8.1
Redhat Enterprise Linux For Power Little Endian Eus=8.2
Redhat Enterprise Linux For Power Little Endian Eus=8.4
Redhat Virtualization Host=4.0
All of
Redhat Software Collections
Redhat Enterprise Linux Server=7.0
All of
Redhat 3scale Api Management=2.0
Any of
Redhat Enterprise Linux=7.0
Redhat Enterprise Linux=8.0
All of
Redhat Codeready Linux Builder
Any of
Redhat Enterprise Linux=8.0
Redhat Enterprise Linux Eus=8.1
Redhat Enterprise Linux Eus=8.2
Redhat Enterprise Linux Eus=8.4
Redhat Enterprise Linux For Power Little Endian=8.0
Redhat Enterprise Linux For Power Little Endian Eus=8.1
Redhat Enterprise Linux For Power Little Endian Eus=8.2
Redhat Enterprise Linux For Power Little Endian Eus=8.4
All of
Redhat Virtualization Host=4.0
Any of
Redhat Enterprise Linux=7.0
Redhat Enterprise Linux=8.0
redhat/kernel<5.14
5.14
debian/linux
5.10.223-1
5.10.226-1
6.1.106-3
6.1.112-1
6.11.4-1
6.11.5-1

Remedy

This vulnerability can be mitigated by disabling the nested virtualization feature: ``` # modprobe -r kvm_amd # modprobe kvm_amd nested=0 ``` Disabling VLS (Virtual VMLOAD/VMSAVE) is an alternative mitigation: ``` # modprobe kvm_amd vls=0 ```

Remedy

https://git.kernel.org/pub/scm/virt/kvm/kvm.git/commit/?id=c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc

Remedy

https://github.com/torvalds/linux/commit/c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc

Remedy

Disable nested virtualisation when loading the KVM AMD module: modprobe kvm_amd nested=0

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