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

Yanan Wang
2020-11-30T12:20:34Z

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 <wangyanan55@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