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KVM: VMX: make rmode_segment_valid() more strict. 

Currently it allows entering vm86 mode if segment limit is greater than
0xffff and db bit is set. Both of those can cause incorrect execution of
instruction by cpu since in vm86 mode limit will be set to 0xffff and db
will be forced to 0.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Gleb Natapov 2012-12-20 16:57:44 +02:00 committed by Marcelo Tosatti
parent 045a282ca4
commit 89efbed02c
1 changed files with 1 additions and 3 deletions
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4
arch/x86/kvm/vmx.c
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@ -3341,15 +3341,13 @@ static bool rmode_segment_valid(struct kvm_vcpu *vcpu, int seg)
vmx_get_segment(vcpu, &var, seg);
var.dpl = 0x3;
var.g = 0;
var.db = 0;
if (seg == VCPU_SREG_CS)
var.type = 0x3;
ar = vmx_segment_access_rights(&var);
if (var.base != (var.selector << 4))
return false;
if (var.limit < 0xffff)
if (var.limit != 0xffff)
return false;
if (ar != 0xf3)
return false;