[PATCH] check shadow_pte == NULL in FNAME(page_fault); drivers/kvm/paging_tmpl.h

[Roel Kluin <12o3l-IWqWACnzNjzz+pZb47iToQ@public.gmane.org>]

#------------------------------------------------------------------------------#
in function FNAME(page_fault), drivers/kvm/paging_tmpl.h, line 450, (linus' git)

I think a check is in place. I am not sure whether this is how it should be
done, nor was the patch below tested. So please review.
--
The u64 pointer shadow_pte is initialized by the function FNAME(fetch), but
FNAME(fetch) can return NULL,

Signed-off-by: Roel Kluin <12o3l-IWqWACnzNjzz+pZb47iToQ@public.gmane.org>
---
diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h
index 4b5391c..fce305d 100644
--- a/drivers/kvm/paging_tmpl.h
+++ b/drivers/kvm/paging_tmpl.h
@@ -460,7 +460,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
 	/*
 	 * mmio: emulate if accessible, otherwise its a guest fault.
 	 */
-	if (is_io_pte(*shadow_pte))
+	if (!shadow_pte || is_io_pte(*shadow_pte))
 		return 1;
 
 	++vcpu->stat.pf_fixed;

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