linux-kernel - [PATCH v2 02/16] KVM: arm64: Check for PTE valitity when checking for executable/cacheable

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Date:   Mon,  4 Oct 2021 18:48:35 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     will@...nel.org, qperret@...gle.com, dbrazdil@...gle.com,
        Steven Price <steven.price@....com>,
        Andrew Jones <drjones@...hat.com>,
        Fuad Tabba <tabba@...gle.com>,
        Srivatsa Vaddagiri <vatsa@...eaurora.org>,
        Shanker R Donthineni <sdonthineni@...dia.com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        kernel-team@...roid.com
Subject: [PATCH v2 02/16] KVM: arm64: Check for PTE valitity when checking for executable/cacheable

Don't blindly assume that the PTE is valid when checking whether
it describes an executable or cacheable mapping.

This makes sure that we don't issue CMOs for invalid mappings.

Suggested-by: Will Deacon <will@...nel.org>
Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 arch/arm64/kvm/hyp/pgtable.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index f8ceebe4982e..6bbfd952f0c5 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -638,12 +638,12 @@ static void stage2_put_pte(kvm_pte_t *ptep, struct kvm_s2_mmu *mmu, u64 addr,
 static bool stage2_pte_cacheable(struct kvm_pgtable *pgt, kvm_pte_t pte)
 {
 	u64 memattr = pte & KVM_PTE_LEAF_ATTR_LO_S2_MEMATTR;
-	return memattr == KVM_S2_MEMATTR(pgt, NORMAL);
+	return kvm_pte_valid(pte) && memattr == KVM_S2_MEMATTR(pgt, NORMAL);
 }
 
 static bool stage2_pte_executable(kvm_pte_t pte)
 {
-	return !(pte & KVM_PTE_LEAF_ATTR_HI_S2_XN);
+	return kvm_pte_valid(pte) && !(pte & KVM_PTE_LEAF_ATTR_HI_S2_XN);
 }
 
 static bool stage2_leaf_mapping_allowed(u64 addr, u64 end, u32 level,
@@ -688,8 +688,7 @@ static int stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level,
 	/* Perform CMOs before installation of the guest stage-2 PTE */
 	if (mm_ops->dcache_clean_inval_poc && stage2_pte_cacheable(pgt, new))
 		mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new, mm_ops),
-						granule);
-
+					       granule);
 	if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
 		mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops), granule);
 
@@ -1091,7 +1090,7 @@ static int stage2_flush_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
 	kvm_pte_t pte = *ptep;
 	kvm_pte_t *pte_follow;
 
-	if (!kvm_pte_valid(pte) || !stage2_pte_cacheable(pgt, pte))
+	if (!stage2_pte_cacheable(pgt, pte))
 		return 0;
 
 	pte_follow = kvm_pte_follow(pte, mm_ops);
-- 
2.30.2