[RFC PATCH 1/3] KVM: arm64: Fix possible memory leak in kvm stage2

[Yanan Wang]

When installing a new leaf pte onto an invalid ptep, we need to get_page(ptep).
When just updating a valid leaf ptep, we shouldn't get_page(ptep).
Incorrect page_count of translation tables might lead to memory leak,
when unmapping a stage 2 memory range.

Signed-off-by: Yanan Wang <wangyana...@huawei.com>
---
 arch/arm64/kvm/hyp/pgtable.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 0271b4a3b9fe..696b6aa83faf 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -186,6 +186,7 @@ static bool kvm_set_valid_leaf_pte(kvm_pte_t *ptep, u64 pa, 
kvm_pte_t attr,
                return old == pte;
 
        smp_store_release(ptep, pte);
+       get_page(virt_to_page(ptep));
        return true;
 }
 
@@ -476,6 +477,7 @@ static bool stage2_map_walker_try_leaf(u64 addr, u64 end, 
u32 level,
        /* There's an existing valid leaf entry, so perform break-before-make */
        kvm_set_invalid_pte(ptep);
        kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, data->mmu, addr, level);
+       put_page(virt_to_page(ptep));
        kvm_set_valid_leaf_pte(ptep, phys, data->attr, level);
 out:
        data->phys += granule;
@@ -512,7 +514,7 @@ static int stage2_map_walk_leaf(u64 addr, u64 end, u32 
level, kvm_pte_t *ptep,
        }
 
        if (stage2_map_walker_try_leaf(addr, end, level, ptep, data))
-               goto out_get_page;
+               return 0;
 
        if (WARN_ON(level == KVM_PGTABLE_MAX_LEVELS - 1))
                return -EINVAL;
@@ -536,9 +538,8 @@ static int stage2_map_walk_leaf(u64 addr, u64 end, u32 
level, kvm_pte_t *ptep,
        }
 
        kvm_set_table_pte(ptep, childp);
-
-out_get_page:
        get_page(page);
+
        return 0;
 }
 
-- 
2.19.1