KVM: VMX: Intercept FS/GS_BASE MSR accesses for 32-bit KVM
stable inclusion from stable-5.10.37 commit 8fcdfa71ba6a1baa7bff73353b914df2a15b1bb8 bugzilla: 51868 CVE: NA -------------------------------- [ Upstream commit dbdd096a ] Disable pass-through of the FS and GS base MSRs for 32-bit KVM. Intel's SDM unequivocally states that the MSRs exist if and only if the CPU supports x86-64. FS_BASE and GS_BASE are mostly a non-issue; a clever guest could opportunistically use the MSRs without issue. KERNEL_GS_BASE is a bigger problem, as a clever guest would subtly be broken if it were migrated, as KVM disallows software access to the MSRs, and unlike the direct variants, KERNEL_GS_BASE needs to be explicitly migrated as it's not captured in the VMCS. Fixes: 25c5f225 ("KVM: VMX: Enable MSR Bitmap feature") Signed-off-by: NSean Christopherson <seanjc@google.com> Message-Id: <20210422023831.3473491-1-seanjc@google.com> [*NOT* for stable kernels. - Paolo] Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com> Signed-off-by: NSasha Levin <sashal@kernel.org> Signed-off-by: NChen Jun <chenjun102@huawei.com> Acked-by: NWeilong Chen <chenweilong@huawei.com> Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
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