Re: [RFC PATCH 1/3] KVM: arm64: Fix possible memory leak in kvm stage2
From: Will Deacon <will@kernel.org>
Date: 2020-11-30 13:22:37
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On Mon, Nov 30, 2020 at 08:18:45PM +0800, Yanan Wang wrote:
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.
Did you find this by inspection, or did you hit this in practice? I'd be interested to see the backtrace for mapping over an existing mapping.
quoted hunk ↗ jump to hunk
Signed-off-by: Yanan Wang <redacted> --- 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));
This is also used for the hypervisor stage-1 page-table, so I'd prefer to leave this function as-is.
quoted hunk ↗ jump to hunk
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;
Isn't this hunk alone sufficient to solve the problem? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel