[PATCH] KVM: Make loading cr3 more robust

Prevent the guest's loading of a corrupt cr3 (pointing at no guest phsyical
page) from crashing the host.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 0675d3e..67c1154 100644 (file)
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -463,7 +463,19 @@ void set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 
        vcpu->cr3 = cr3;
        spin_lock(&vcpu->kvm->lock);
-       vcpu->mmu.new_cr3(vcpu);
+       /*
+        * Does the new cr3 value map to physical memory? (Note, we
+        * catch an invalid cr3 even in real-mode, because it would
+        * cause trouble later on when we turn on paging anyway.)
+        *
+        * A real CPU would silently accept an invalid cr3 and would
+        * attempt to use it - with largely undefined (and often hard
+        * to debug) behavior on the guest side.
+        */
+       if (unlikely(!gfn_to_memslot(vcpu->kvm, cr3 >> PAGE_SHIFT)))
+               inject_gp(vcpu);
+       else
+               vcpu->mmu.new_cr3(vcpu);
        spin_unlock(&vcpu->kvm->lock);
 }
 EXPORT_SYMBOL_GPL(set_cr3);