On 05/11/2010 07:52 PM, Mohammed Gamal wrote:
- Add 's' and 'g' field checks on segment registers
- Correct SS checks for request and descriptor privilege levels
Signed-off-by: Mohammed Gamal<m.gamal005@xxxxxxxxx>
---
arch/x86/kvm/vmx.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++----
1 files changed, 67 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 777e00d..9805c2a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2121,16 +2121,30 @@ static bool stack_segment_valid(struct kvm_vcpu *vcpu)
vmx_get_segment(vcpu,&ss, VCPU_SREG_SS);
ss_rpl = ss.selector& SELECTOR_RPL_MASK;
- if (ss.unusable)
+ if (ss.dpl != ss_rpl) /* DPL != RPL */
+ return false;
+
+ if (ss.unusable) /* Short-circuit */
return true;
If ss.unusable, do the dpl and rpl have any meaning?
if (!ss.present)
return false;
+ if (ss.limit& 0xfff00000) {
+ if ((ss.limit& 0xfff)< 0xfff)
+ return false;
+ if (!ss.g)
+ return false;
+ } else {
+ if ((ss.limit& 0xfff) == 0xfff)
+ return false;
+ if (ss.g)
+ return false;
+ }
There is no architectural way to break this. That is, without
virtualization, there is no way a real cpu will ever have a limit of
0x12345678.
We need to distinguish between big real mode and real mode that can be
virtualized using vm86, but we don't need to consider impossible setups.
@@ -2143,8 +2157,15 @@ static bool data_segment_valid(struct kvm_vcpu *vcpu, int seg)
vmx_get_segment(vcpu,&var, seg);
rpl = var.selector& SELECTOR_RPL_MASK;
- if (var.unusable)
+ if (var.unusable) /* Short-circuit */
return true;
+ if (!(var.type& AR_TYPE_ACCESSES_MASK))
+ return false;
Again, there is no architectural way for a segment not to have the
accessed bit set.
+ if (var.type& AR_TYPE_CODE_MASK) {
+ if (!(var.type& AR_TYPE_READABLE_MASK))
+ return false;
+ }
About this, I'm not sure.
+
if (!var.s)
return false;
if (!var.present)
@@ -2154,6 +2175,18 @@ static bool data_segment_valid(struct kvm_vcpu *vcpu, int seg)
return false;
}
+ if (var.limit& 0xfff00000) {
+ if ((var.limit& 0xfff)< 0xfff)
+ return false;
+ if (!var.g)
+ return false;
+ } else {
+ if ((var.limit& 0xfff) == 0xfff)
+ return false;
+ if (var.g)
+ return false;
+ }
Even disregarding the incorrectness, you shouldn't duplicate code like this.
@@ -2192,6 +2240,20 @@ static bool ldtr_valid(struct kvm_vcpu *vcpu)
return false;
if (!ldtr.present)
return false;
+ if (ldtr.s)
+ return false;
Architecturally impossible.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
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