[PATCH 4.19 38/38] KVM: x86/mmu: Fix struct guest_walker arrays for 5-level paging

[Greg Kroah-Hartman]

From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>

[ Upstream commit f6ab0107a4942dbf9a5cf0cca3f37e184870a360 ]

Define PT_MAX_FULL_LEVELS as PT64_ROOT_MAX_LEVEL, i.e. 5, to fix shadow
paging for 5-level guest page tables.  PT_MAX_FULL_LEVELS is used to
size the arrays that track guest pages table information, i.e. using a
"max levels" of 4 causes KVM to access garbage beyond the end of an
array when querying state for level 5 entries.  E.g. FNAME(gpte_changed)
will read garbage and most likely return %true for a level 5 entry,
soft-hanging the guest because FNAME(fetch) will restart the guest
instead of creating SPTEs because it thinks the guest PTE has changed.

Note, KVM doesn't yet support 5-level nested EPT, so PT_MAX_FULL_LEVELS
gets to stay "4" for the PTTYPE_EPT case.

Fixes: 855feb673640 ("KVM: MMU: Add 5 level EPT & Shadow page table support.")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 arch/x86/kvm/paging_tmpl.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 100ae4fabf170..61f10a4fd8074 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -36,7 +36,7 @@
 	#define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT
 	#define PT_HAVE_ACCESSED_DIRTY(mmu) true
 	#ifdef CONFIG_X86_64
-	#define PT_MAX_FULL_LEVELS 4
+	#define PT_MAX_FULL_LEVELS PT64_ROOT_MAX_LEVEL
 	#define CMPXCHG cmpxchg
 	#else
 	#define CMPXCHG cmpxchg64
-- 
2.20.1