From: Liran Alon <liran.alon@oracle.com>
To: pbonzini@redhat.com, rkrcmar@redhat.com, kvm@vger.kernel.org
Cc: max@m00nbsd.net, Liran Alon <liran.alon@oracle.com>,
Joao Martins <joao.m.martins@oracle.com>
Subject: [PATCH] KVM: nVMX: Ignore segment base for VMX memory operand when segment not FS or GS
Date: Mon, 15 Jul 2019 18:47:44 +0300 [thread overview]
Message-ID: <20190715154744.36134-1-liran.alon@oracle.com> (raw)
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>
---
arch/x86/kvm/vmx/nested.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 18efb338ed8a..e01e1b6b8167 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4068,6 +4068,8 @@ 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.
*/
+ if ((seg_reg != VCPU_SREG_FS) && (seg_reg != VCPU_SREG_GS))
+ s.base = 0;
*ret = s.base + off;
/* Long mode: #GP(0)/#SS(0) if the memory address is in a
--
2.20.1
next reply other threads:[~2019-07-15 15:48 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-15 15:47 Liran Alon [this message]
2019-07-15 16:22 ` [PATCH] KVM: nVMX: Ignore segment base for VMX memory operand when segment not FS or GS Vitaly Kuznetsov
2019-07-15 17:21 ` Sean Christopherson
2019-07-15 18:28 ` Paolo Bonzini
2019-07-15 18:30 ` Liran Alon
2019-07-15 18:44 ` Sean Christopherson
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