linux-kernel - [PATCH v2 1/3] KVM: arm64: Fix possible memory leak in kvm stage2

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Message-ID: <20201201201034.116760-2-wangyanan55@huawei.com>
Date:   Wed, 2 Dec 2020 04:10:32 +0800
From:   Yanan Wang <wangyanan55@...wei.com>
To:     <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        Marc Zyngier <maz@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        James Morse <james.morse@....com>,
        "Julien Thierry" <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Gavin Shan <gshan@...hat.com>,
        Quentin Perret <qperret@...gle.com>
CC:     <wanghaibin.wang@...wei.com>, <yezengruan@...wei.com>,
        <zhukeqian1@...wei.com>, <yuzenghui@...wei.com>,
        <jiangkunkun@...wei.com>, <wangjingyi11@...wei.com>,
        <lushenming@...wei.com>, Yanan Wang <wangyanan55@...wei.com>
Subject: [PATCH v2 1/3] KVM: arm64: Fix possible memory leak in kvm stage2

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@...wei.com>
---
 arch/arm64/kvm/hyp/pgtable.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 0271b4a3b9fe..b232bdd142a6 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -470,6 +470,9 @@ 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 (kvm_pte_valid(*ptep))
+		put_page(virt_to_page(ptep));
+
 	if (kvm_set_valid_leaf_pte(ptep, phys, data->attr, level))
 		goto out;
 
-- 
2.19.1