KVM: arm64: Prevent unconditional donation of unmapped regions from the host

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@google.com>
Fixes: e82edcc75c4e ("KVM: arm64: Implement do_share() helper for sharing memory")
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230518095844.1178-1-will@kernel.org

diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 2e9ec4a..a8813b2 100644 (file)
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -575,7 +575,7 @@ struct pkvm_mem_donation {
 
 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(const struct kvm_pgtable_visit_ctx *ctx,
@@ -583,10 +583,7 @@ static int __check_page_state_visitor(const struct kvm_pgtable_visit_ctx *ctx,
 {
        struct check_walk_data *d = ctx->arg;
 
-       if (kvm_pte_valid(ctx->old) && !addr_is_allowed_memory(kvm_pte_to_phys(ctx->old)))
-               return -EINVAL;
-
-       return d->get_page_state(ctx->old) == d->desired ? 0 : -EPERM;
+       return d->get_page_state(ctx->old, ctx->addr) == d->desired ? 0 : -EPERM;
 }
 
 static int check_page_state_range(struct kvm_pgtable *pgt, u64 addr, u64 size,
@@ -601,8 +598,11 @@ 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;
 
@@ -709,7 +709,7 @@ static int host_complete_donation(u64 addr, const struct pkvm_mem_transition *tx
        return host_stage2_set_owner_locked(addr, size, host_id);
 }
 
-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;