From 6694e48012826351036fd10fc506ca880023e25f Mon Sep 17 00:00:00 2001
From: Liran Alon <liran.alon@oracle.com>
Date: Mon, 15 Jul 2019 18:47:44 +0300
Subject: [PATCH] KVM: nVMX: Ignore segment base for VMX memory operand when
segment not FS or GS
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>
---
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 bb509c2549397..4f23e34f628b6 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4194,7 +4194,10 @@ 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
--
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