| Message ID | 20190715154744.36134-1-liran.alon@oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: nVMX: Ignore segment base for VMX memory operand when segment not FS or GS | expand |
Liran Alon <liran.alon@oracle.com> writes: > 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; (personal preference) I'd rather write this as /* In long mode only FS and GS bases are considered */ if (seg_reg == VCPU_SREG_FS || seg_reg == VCPU_SREG_GS) *ret = s.base + off; else *ret = off; > *ret = s.base + off; > > /* Long mode: #GP(0)/#SS(0) if the memory address is in a As-is or rewritten with my suggestion, Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
On Mon, Jul 15, 2019 at 06:22:52PM +0200, Vitaly Kuznetsov wrote: > Liran Alon <liran.alon@oracle.com> writes: > > > 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)) I'm pretty sure the internal parantheses are unnecessary. > > + s.base = 0; > > (personal preference) > > I'd rather write this as > > /* In long mode only FS and GS bases are considered */ > if (seg_reg == VCPU_SREG_FS || seg_reg == VCPU_SREG_GS) > *ret = s.base + off; > else > *ret = off; > > > *ret = s.base + off; > > > > /* Long mode: #GP(0)/#SS(0) if the memory address is in a > > As-is or rewritten with my suggestion, Likewise, Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com> > > Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> > > -- > Vitaly
On 15/07/19 19:21, Sean Christopherson wrote: >>> + if ((seg_reg != VCPU_SREG_FS) && (seg_reg != VCPU_SREG_GS)) > I'm pretty sure the internal parantheses are unnecessary. > Indeed, that's so Pascal! :) I'll apply Vitaly's suggestion and queue it. Paolo
> On 15 Jul 2019, at 21:28, Paolo Bonzini <pbonzini@redhat.com> wrote: > > On 15/07/19 19:21, Sean Christopherson wrote: >>>> + if ((seg_reg != VCPU_SREG_FS) && (seg_reg != VCPU_SREG_GS)) >> I'm pretty sure the internal parantheses are unnecessary. >> > > Indeed, that's so Pascal! :) I'll apply Vitaly's suggestion and queue it. > > Paolo I like parentheses as it makes ordering of expression a no-brainer. But that’s just a matter of taste I guess. I don’t mind you will change it according to given suggestions. :) -Liran
On Mon, Jul 15, 2019 at 09:30:48PM +0300, Liran Alon wrote:
> I like parentheses as it makes ordering of expression a no-brainer.
Matching parantheses is not my forte :-)
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
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(+)