[PATCH 12/24] kvm: x86/kvm: RCU dereference tdp mmu page table links

[Ben Gardon]

In order to protect TDP MMU PT memory with RCU, ensure that page table
links are properly rcu_derefenced.

Reviewed-by: Peter Feiner <pfeiner@xxxxxxxxxx>

Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx>
---
 arch/x86/kvm/mmu/tdp_iter.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/tdp_iter.c b/arch/x86/kvm/mmu/tdp_iter.c
index 87b7e16911db..82855613ffa0 100644
--- a/arch/x86/kvm/mmu/tdp_iter.c
+++ b/arch/x86/kvm/mmu/tdp_iter.c
@@ -49,6 +49,8 @@ void tdp_iter_start(struct tdp_iter *iter, u64 *root_pt, int root_level,
  */
 u64 *spte_to_child_pt(u64 spte, int level)
 {
+	u64 *child_pt;
+
 	/*
 	 * There's no child entry if this entry isn't present or is a
 	 * last-level entry.
@@ -56,7 +58,9 @@ u64 *spte_to_child_pt(u64 spte, int level)
 	if (!is_shadow_present_pte(spte) || is_last_spte(spte, level))
 		return NULL;
 
-	return __va(spte_to_pfn(spte) << PAGE_SHIFT);
+	child_pt = __va(spte_to_pfn(spte) << PAGE_SHIFT);
+
+	return rcu_dereference(child_pt);
 }
 
 /*
-- 
2.30.0.284.gd98b1dd5eaa7-goog