diff --git a/libraries/libmesosphere/source/kern_k_thread.cpp b/libraries/libmesosphere/source/kern_k_thread.cpp
index d2d5581dd..fd6ed1637 100644
--- a/libraries/libmesosphere/source/kern_k_thread.cpp
+++ b/libraries/libmesosphere/source/kern_k_thread.cpp
@@ -599,14 +599,16 @@ namespace ams::kern {
             KScopedSchedulerLock sl;
             MESOSPHERE_ASSERT(m_num_core_migration_disables >= 0);
 
-            /* If the core id is no-update magic, preserve the ideal core id. */
-            if (core_id == ams::svc::IdealCoreNoUpdate) {
+            /* If we're updating, set our ideal virtual core. */
+            if (core_id != ams::svc::IdealCoreNoUpdate) {
+                m_virtual_ideal_core_id = core_id;
+            } else {
+                /* Preserve our ideal core id. */
                 core_id = m_virtual_ideal_core_id;
                 R_UNLESS(((1ul << core_id) & v_affinity_mask) != 0, svc::ResultInvalidCombination());
             }
 
-            /* Set the virtual core/affinity mask. */
-            m_virtual_ideal_core_id = core_id;
+            /* Set our affinity mask. */
             m_virtual_affinity_mask = v_affinity_mask;
 
             /* Translate the virtual core to a physical core. */
diff --git a/libraries/libmesosphere/source/svc/kern_svc_thread.cpp b/libraries/libmesosphere/source/svc/kern_svc_thread.cpp
index c887c5f56..3c511008b 100644
--- a/libraries/libmesosphere/source/svc/kern_svc_thread.cpp
+++ b/libraries/libmesosphere/source/svc/kern_svc_thread.cpp
@@ -132,14 +132,17 @@ namespace ams::kern::svc {
             /* Get the current process. */
             KProcess &process = GetCurrentProcess();
 
-            /* Validate the priority. */
-            R_UNLESS(ams::svc::HighestThreadPriority <= priority && priority <= ams::svc::LowestThreadPriority, svc::ResultInvalidPriority());
-            R_UNLESS(process.CheckThreadPriority(priority),                                                     svc::ResultInvalidPriority());
-
             /* Get the thread from its handle. */
             KScopedAutoObject thread = process.GetHandleTable().GetObject<KThread>(thread_handle);
             R_UNLESS(thread.IsNotNull(), svc::ResultInvalidHandle());
 
+            /* Validate the thread is owned by the current process. */
+            R_UNLESS(thread->GetOwnerProcess() == GetCurrentProcessPointer(), svc::ResultInvalidHandle());
+
+            /* Validate the priority. */
+            R_UNLESS(ams::svc::HighestThreadPriority <= priority && priority <= ams::svc::LowestThreadPriority, svc::ResultInvalidPriority());
+            R_UNLESS(process.CheckThreadPriority(priority),                                                     svc::ResultInvalidPriority());
+
             /* Set the thread priority. */
             thread->SetBasePriority(priority);
             return ResultSuccess();
@@ -157,6 +160,13 @@ namespace ams::kern::svc {
         }
 
         Result SetThreadCoreMask(ams::svc::Handle thread_handle, int32_t core_id, uint64_t affinity_mask) {
+            /* Get the thread from its handle. */
+            KScopedAutoObject thread = GetCurrentProcess().GetHandleTable().GetObject<KThread>(thread_handle);
+            R_UNLESS(thread.IsNotNull(), svc::ResultInvalidHandle());
+
+            /* Validate the thread is owned by the current process. */
+            R_UNLESS(thread->GetOwnerProcess() == GetCurrentProcessPointer(), svc::ResultInvalidHandle());
+
             /* Determine the core id/affinity mask. */
             if (core_id == ams::svc::IdealCoreUseProcessValue) {
                 core_id       = GetCurrentProcess().GetIdealCoreId();
@@ -175,10 +185,6 @@ namespace ams::kern::svc {
                 }
             }
 
-            /* Get the thread from its handle. */
-            KScopedAutoObject thread = GetCurrentProcess().GetHandleTable().GetObject<KThread>(thread_handle);
-            R_UNLESS(thread.IsNotNull(), svc::ResultInvalidHandle());
-
             /* Set the core mask. */
             R_TRY(thread->SetCoreMask(core_id, affinity_mask));