[Bug 204175] New: Segmentation: incorrect base calculation in VMX

[Bug 204175] New: Segmentation: incorrect base calculation in VMX

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=204175

            Bug ID: 204175
           Summary: Segmentation: incorrect base calculation in VMX
           Product: Virtualization
           Version: unspecified
    Kernel Version: 5.*
          Hardware: Intel
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: kvm
          Assignee: virtualization_kvm@kernel-bugs.osdl.org
          Reporter: max@m00nbsd.net
        Regression: No

In vmx/nested.c::get_vmx_mem_address(), when the guest runs in long mode, the
base address of the memory operand is computed with a simple:

    *ret = s.base + off;

This is incorrect, the base applies only to FS and GS, not to the others.

Because of that, if the guest uses a VMX instruction based on DS and has a
DS.base that is non-zero, KVM wrongfully adds the base to the resulting
address.

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