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authorYanan Wang <wangyanan55@huawei.com>2020-12-02 04:10:32 +0800
committerMarc Zyngier <maz@kernel.org>2020-12-02 09:42:24 +0000
commit5c646b7e1d8bcb12317426287c516dfa4c5171c2 (patch)
treee898f5189dcf00d995c7c7b36a9c8a29298167b3 /arch
parent23bde34771f1ea92fb5e6682c0d8c04304d34b3b (diff)
KVM: arm64: Fix memory leak on stage2 update of a valid PTE
When installing a new leaf PTE onto an invalid ptep, we need to get_page(ptep) to account for the new mapping. However, simply updating a valid PTE shouldn't result in any additional refcounting, as there is new mapping. This otherwise results in a page being forever wasted. Address this by fixing-up the refcount in stage2_map_walker_try_leaf() if the PTE was already valid, balancing out the later get_page() in stage2_map_walk_leaf(). Signed-off-by: Yanan Wang <wangyanan55@huawei.com> [maz: update commit message, add comment in the code] Signed-off-by: Marc Zyngier <maz@kernel.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20201201201034.116760-2-wangyanan55@huawei.com
Diffstat (limited to 'arch')
-rw-r--r--arch/arm64/kvm/hyp/pgtable.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 0271b4a3b9fe..2beba1dc40ec 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -470,6 +470,15 @@ static bool stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level,
if (!kvm_block_mapping_supported(addr, end, phys, level))
return false;
+ /*
+ * If the PTE was already valid, drop the refcount on the table
+ * early, as it will be bumped-up again in stage2_map_walk_leaf().
+ * This ensures that the refcount stays constant across a valid to
+ * valid PTE update.
+ */
+ if (kvm_pte_valid(*ptep))
+ put_page(virt_to_page(ptep));
+
if (kvm_set_valid_leaf_pte(ptep, phys, data->attr, level))
goto out;