From: Liran Alon liran.alon@oracle.com
[ Upstream commit 6694e48012826351036fd10fc506ca880023e25f ]
As reported by Maxime at https://bugzilla.kernel.org/show_bug.cgi?id=204175:
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.
Reported-by: Maxime Villard max@m00nbsd.net Reviewed-by: Joao Martins joao.m.martins@oracle.com Signed-off-by: Liran Alon liran.alon@oracle.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kvm/vmx/nested.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 46af3a5e9209..aa949ab7850c 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -4068,7 +4068,10 @@ int get_vmx_mem_address(struct kvm_vcpu *vcpu, unsigned long exit_qualification, * mode, e.g. a 32-bit address size can yield a 64-bit virtual * address when using FS/GS with a non-zero base. */ - *ret = s.base + off; + if (seg_reg == VCPU_SREG_FS || seg_reg == VCPU_SREG_GS) + *ret = s.base + off; + else + *ret = off;
/* Long mode: #GP(0)/#SS(0) if the memory address is in a * non-canonical form. This is the only check on the memory