[PATCH v7 7/7] KVM: arm64: Enforce strict SBZ checks in the FF-A proxy

[Sebastian Ene <sebastianene@google.com>]

Introduce a helper method ffa_check_unused_args_sbz to enforce strict
arguments checking when the hypervisor acts as a relayer between the
host and Trustzone.

Signed-off-by: Sebastian Ene <sebastianene@google.com>
Reviewed-by: Vincent Donnefort <vdonnefort@google.com>
Acked-by: Will Deacon <will@kernel.org>
---
 arch/arm64/kvm/hyp/nvhe/ffa.c | 96 ++++++++++++++++++++++++++++++++++-
 1 file changed, 95 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index 712811e89435..334f8a28d942 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -74,6 +74,21 @@ static u32 hyp_ffa_version;
 static bool has_version_negotiated;
 static hyp_spinlock_t version_lock;
 
+static bool ffa_check_unused_args_sbz(struct kvm_cpu_context *ctxt, int first_reg)
+{
+	DECLARE_REG(u32, func_id, ctxt, 0);
+	int reg, end_reg = 7;
+
+	if (hyp_ffa_version >= FFA_VERSION_1_2 && ARM_SMCCC_IS_64(func_id))
+		end_reg = 17;
+	for (reg = first_reg; reg <= end_reg; reg++) {
+		if (cpu_reg(ctxt, reg))
+			return true;
+	}
+
+	return false;
+}
+
 static void ffa_to_smccc_error(struct arm_smccc_1_2_regs *res, u64 ffa_errno)
 {
 	*res = (struct arm_smccc_1_2_regs) {
@@ -242,6 +257,11 @@ static void do_ffa_rxtx_map(struct arm_smccc_1_2_regs *res,
 	int ret = 0;
 	void *rx_virt, *tx_virt;
 
+	if (ffa_check_unused_args_sbz(ctxt, 4)) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto out;
+	}
+
 	if (npages != (KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) / FFA_PAGE_SIZE) {
 		ret = FFA_RET_INVALID_PARAMETERS;
 		goto out;
@@ -318,6 +338,11 @@ static void do_ffa_rxtx_unmap(struct arm_smccc_1_2_regs *res,
 	DECLARE_REG(u32, id, ctxt, 1);
 	int ret = 0;
 
+	if (ffa_check_unused_args_sbz(ctxt, 2)) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto out;
+	}
+
 	if (id != HOST_FFA_ID) {
 		ret = FFA_RET_INVALID_PARAMETERS;
 		goto out;
@@ -424,6 +449,11 @@ static void do_ffa_mem_frag_tx(struct arm_smccc_1_2_regs *res,
 	int ret = FFA_RET_INVALID_PARAMETERS;
 	u32 nr_ranges;
 
+	if (ffa_check_unused_args_sbz(ctxt, 5)) {
+		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
+		return;
+	}
+
 	if (fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE)
 		goto out;
 
@@ -485,6 +515,11 @@ static void __do_ffa_mem_xfer(const u64 func_id,
 	u32 offset, nr_ranges, checked_offset;
 	int ret = 0;
 
+	if (ffa_check_unused_args_sbz(ctxt, 5)) {
+		ret = FFA_RET_INVALID_PARAMETERS;
+		goto out;
+	}
+
 	if (addr_mbz || npages_mbz || fraglen > len ||
 	    fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) {
 		ret = FFA_RET_INVALID_PARAMETERS;
@@ -584,6 +619,11 @@ static void do_ffa_mem_reclaim(struct arm_smccc_1_2_regs *res,
 	int ret = 0;
 	u64 handle;
 
+	if (ffa_check_unused_args_sbz(ctxt, 4)) {
+		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
+		return;
+	}
+
 	handle = PACK_HANDLE(handle_lo, handle_hi);
 
 	hyp_spin_lock(&host_buffers.lock);
@@ -764,6 +804,11 @@ static void do_ffa_version(struct arm_smccc_1_2_regs *res,
 {
 	DECLARE_REG(u32, ffa_req_version, ctxt, 1);
 
+	if (ffa_check_unused_args_sbz(ctxt, 2)) {
+		res->a0 = FFA_RET_NOT_SUPPORTED;
+		return;
+	}
+
 	if (FFA_MAJOR_VERSION(ffa_req_version) != 1) {
 		res->a0 = FFA_RET_NOT_SUPPORTED;
 		return;
@@ -813,6 +858,11 @@ static void do_ffa_part_get(struct arm_smccc_1_2_regs *res,
 	DECLARE_REG(u32, flags, ctxt, 5);
 	u32 count, partition_sz, copy_sz;
 
+	if (ffa_check_unused_args_sbz(ctxt, 6)) {
+		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
+		return;
+	}
+
 	hyp_spin_lock(&host_buffers.lock);
 	if (!host_buffers.rx) {
 		ffa_to_smccc_res(res, FFA_RET_BUSY);
@@ -860,9 +910,15 @@ static void do_ffa_part_get(struct arm_smccc_1_2_regs *res,
 static void do_ffa_notif_bitmap(struct arm_smccc_1_2_regs *res,
 				struct kvm_cpu_context *ctxt)
 {
+	DECLARE_REG(u32, func_id, ctxt, 0);
 	DECLARE_REG(u32, vmid, ctxt, 1);
 	struct arm_smccc_1_2_regs *args;
 
+	if (ffa_check_unused_args_sbz(ctxt, func_id == FFA_NOTIFICATION_BITMAP_CREATE ? 3 : 2)) {
+		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
+		return;
+	}
+
 	if (vmid != HOST_FFA_ID) {
 		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
 		return;
@@ -879,6 +935,11 @@ static void do_ffa_notif_bind(struct arm_smccc_1_2_regs *res,
 	DECLARE_REG(u32, flags, ctxt, 2);
 	struct arm_smccc_1_2_regs *args;
 
+	if (ffa_check_unused_args_sbz(ctxt, 5)) {
+		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
+		return;
+	}
+
 	if (FIELD_GET(FFA_NOTIF_RECEIVER_ENDP_MASK, endp_id) != HOST_FFA_ID) {
 		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
 		return;
@@ -900,7 +961,7 @@ static void do_ffa_notif_unbind(struct arm_smccc_1_2_regs *res,
 	DECLARE_REG(u32, reserved, ctxt, 2);
 	struct arm_smccc_1_2_regs *args;
 
-	if (reserved) {
+	if (ffa_check_unused_args_sbz(ctxt, 5) || reserved) {
 		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
 		return;
 	}
@@ -926,6 +987,11 @@ static void do_ffa_notif_set(struct arm_smccc_1_2_regs *res,
 		return;
 	}
 
+	if (ffa_check_unused_args_sbz(ctxt, 5)) {
+		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
+		return;
+	}
+
 	if (flags & GENMASK(15, 2)) {
 		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
 		return;
@@ -947,6 +1013,11 @@ static void do_ffa_notif_get(struct arm_smccc_1_2_regs *res,
 		return;
 	}
 
+	if (ffa_check_unused_args_sbz(ctxt, 3)) {
+		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
+		return;
+	}
+
 	if (flags & GENMASK(31, 4)) {
 		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
 		return;
@@ -956,6 +1027,20 @@ static void do_ffa_notif_get(struct arm_smccc_1_2_regs *res,
 	hyp_smccc_1_2_smc(args, res);
 }
 
+static void do_ffa_notif_info_get(struct arm_smccc_1_2_regs *res,
+				  struct kvm_cpu_context *ctxt)
+{
+	struct arm_smccc_1_2_regs *args;
+
+	if (ffa_check_unused_args_sbz(ctxt, 1)) {
+		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
+		return;
+	}
+
+	args = (void *)&ctxt->regs.regs[0];
+	hyp_smccc_1_2_smc(args, res);
+}
+
 bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
 {
 	struct arm_smccc_1_2_regs res;
@@ -984,6 +1069,11 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
 
 	switch (func_id) {
 	case FFA_FEATURES:
+		if (ffa_check_unused_args_sbz(host_ctxt, 3)) {
+			ffa_to_smccc_res(&res, FFA_RET_INVALID_PARAMETERS);
+			goto out_handled;
+		}
+
 		if (!do_ffa_features(&res, host_ctxt))
 			return false;
 		goto out_handled;
@@ -1030,6 +1120,10 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
 	case FFA_NOTIFICATION_GET:
 		do_ffa_notif_get(&res, host_ctxt);
 		goto out_handled;
+	case FFA_NOTIFICATION_INFO_GET:
+	case FFA_FN64_NOTIFICATION_INFO_GET:
+		do_ffa_notif_info_get(&res, host_ctxt);
+		goto out_handled;
 	}
 
 	if (ffa_call_supported(func_id))
-- 
2.55.0.rc0.799.gd6f94ed593-goog