KVM: cpuid: Fix read/write out-of-bounds vulnerability in cpuid emulation

[pandora-kernel.git] / arch / x86 / kvm / x86.c

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0a0ffda..ca35c52 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5450,18 +5450,20 @@ int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt)
 static int move_to_next_stateful_cpuid_entry(struct kvm_vcpu *vcpu, int i)
 {
        struct kvm_cpuid_entry2 *e = &vcpu->arch.cpuid_entries[i];
-       int j, nent = vcpu->arch.cpuid_nent;
+       struct kvm_cpuid_entry2 *ej;
+       int j = i;
+       int nent = vcpu->arch.cpuid_nent;
 
        e->flags &= ~KVM_CPUID_FLAG_STATE_READ_NEXT;
        /* when no next entry is found, the current entry[i] is reselected */
-       for (j = i + 1; ; j = (j + 1) % nent) {
-               struct kvm_cpuid_entry2 *ej = &vcpu->arch.cpuid_entries[j];
-               if (ej->function == e->function) {
-                       ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
-                       return j;
-               }
-       }
-       return 0; /* silence gcc, even though control never reaches here */
+       do {
+               j = (j + 1) % nent;
+               ej = &vcpu->arch.cpuid_entries[j];
+       } while (ej->function != e->function);
+
+       ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
+
+       return j;
 }
 
 /* find an entry with matching function, matching index (if needed), and that