linux-kernel - [PATCH stable 6.1.y 2/2] KVM: arm64: Prevent unconditional donation of unmapped regions from the host

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Message-ID: <20230920192729.694309-2-surajjs@amazon.com>
Date:   Wed, 20 Sep 2023 12:27:29 -0700
From:   Suraj Jitindar Singh <surajjs@...zon.com>
To:     <stable@...r.kernel.org>
CC:     <james.morse@....com>, <alexandru.elisei@....com>,
        <suzuki.poulose@....com>, <oliver.upton@...ux.dev>,
        <catalin.marinas@....com>, <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.linux.dev>, <kvmarm@...ts.cs.columbia.edu>,
        <linux-kernel@...r.kernel.org>, <sjitindarsingh@...il.com>,
        Will Deacon <will@...nel.org>,
        Quentin Perret <qperret@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Suraj Jitindar Singh <surajjs@...zon.com>
Subject: [PATCH stable 6.1.y 2/2] KVM: arm64: Prevent unconditional donation of unmapped regions from the host

From: Will Deacon <will@...nel.org>

commit 09cce60bddd6461a93a5bf434265a47827d1bc6f upstream.

Since host stage-2 mappings are created lazily, we cannot rely solely on
the pte in order to recover the target physical address when checking a
host-initiated memory transition as this permits donation of unmapped
regions corresponding to MMIO or "no-map" memory.

Instead of inspecting the pte, move the addr_is_allowed_memory() check
into the host callback function where it is passed the physical address
directly from the walker.

Cc: Quentin Perret <qperret@...gle.com>
Fixes: e82edcc75c4e ("KVM: arm64: Implement do_share() helper for sharing memory")
Signed-off-by: Will Deacon <will@...nel.org>
Signed-off-by: Marc Zyngier <maz@...nel.org>
Link: https://lore.kernel.org/r/20230518095844.1178-1-will@kernel.org
[ bp: s/ctx->addr/addr in __check_page_state_visitor due to missing commit
      "KVM: arm64: Combine visitor arguments into a context structure"
      in stable.
]
Signed-off-by: Suraj Jitindar Singh <surajjs@...zon.com>
---
 arch/arm64/kvm/hyp/nvhe/mem_protect.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 0f6c053686c7..0faa330a41ed 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -424,7 +424,7 @@ struct pkvm_mem_share {
 
 struct check_walk_data {
 	enum pkvm_page_state	desired;
-	enum pkvm_page_state	(*get_page_state)(kvm_pte_t pte);
+	enum pkvm_page_state	(*get_page_state)(kvm_pte_t pte, u64 addr);
 };
 
 static int __check_page_state_visitor(u64 addr, u64 end, u32 level,
@@ -435,10 +435,7 @@ static int __check_page_state_visitor(u64 addr, u64 end, u32 level,
 	struct check_walk_data *d = arg;
 	kvm_pte_t pte = *ptep;
 
-	if (kvm_pte_valid(pte) && !addr_is_allowed_memory(kvm_pte_to_phys(pte)))
-		return -EINVAL;
-
-	return d->get_page_state(pte) == d->desired ? 0 : -EPERM;
+	return d->get_page_state(pte, addr) == d->desired ? 0 : -EPERM;
 }
 
 static int check_page_state_range(struct kvm_pgtable *pgt, u64 addr, u64 size,
@@ -453,8 +450,11 @@ static int check_page_state_range(struct kvm_pgtable *pgt, u64 addr, u64 size,
 	return kvm_pgtable_walk(pgt, addr, size, &walker);
 }
 
-static enum pkvm_page_state host_get_page_state(kvm_pte_t pte)
+static enum pkvm_page_state host_get_page_state(kvm_pte_t pte, u64 addr)
 {
+	if (!addr_is_allowed_memory(addr))
+		return PKVM_NOPAGE;
+
 	if (!kvm_pte_valid(pte) && pte)
 		return PKVM_NOPAGE;
 
@@ -521,7 +521,7 @@ static int host_initiate_unshare(u64 *completer_addr,
 	return __host_set_page_state_range(addr, size, PKVM_PAGE_OWNED);
 }
 
-static enum pkvm_page_state hyp_get_page_state(kvm_pte_t pte)
+static enum pkvm_page_state hyp_get_page_state(kvm_pte_t pte, u64 addr)
 {
 	if (!kvm_pte_valid(pte))
 		return PKVM_NOPAGE;
-- 
2.34.1