Commit 09cce60b authored by Will Deacon's avatar Will Deacon Committed by Marc Zyngier
Browse files

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: e82edcc7 ("KVM: arm64: Implement do_share() helper for sharing memory")
Signed-off-by: default avatarWill Deacon <will@kernel.org>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230518095844.1178-1-will@kernel.org
parent 62548732

arch/arm64/kvm/hyp/nvhe/mem_protect.c

+7 −7
Original line number Diff line number Diff line
@@ -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;