diff --git a/media/libaudioclient/IAudioPolicyService.cpp b/media/libaudioclient/IAudioPolicyService.cpp
index 970ae90..53bc1b7 100644
--- a/media/libaudioclient/IAudioPolicyService.cpp
+++ b/media/libaudioclient/IAudioPolicyService.cpp
@@ -22,6 +22,7 @@
 #include <math.h>
 #include <sys/types.h>
 
+#include <binder/IPCThreadState.h>
 #include <binder/Parcel.h>
 
 #include <media/AudioEffect.h>
@@ -831,10 +832,33 @@
 
 // ----------------------------------------------------------------------
 
-
 status_t BnAudioPolicyService::onTransact(
     uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
 {
+    // make sure transactions reserved to AudioFlinger do not come from other processes
+    switch (code) {
+        case START_OUTPUT:
+        case STOP_OUTPUT:
+        case RELEASE_OUTPUT:
+        case GET_INPUT_FOR_ATTR:
+        case START_INPUT:
+        case STOP_INPUT:
+        case RELEASE_INPUT:
+        case GET_STRATEGY_FOR_STREAM:
+        case GET_OUTPUT_FOR_EFFECT:
+        case REGISTER_EFFECT:
+        case UNREGISTER_EFFECT:
+        case SET_EFFECT_ENABLED:
+        case GET_OUTPUT_FOR_ATTR:
+        case ACQUIRE_SOUNDTRIGGER_SESSION:
+        case RELEASE_SOUNDTRIGGER_SESSION:
+            ALOGW("%s: transaction %d received from PID %d",
+                  __func__, code, IPCThreadState::self()->getCallingPid());
+            return INVALID_OPERATION;
+        default:
+            break;
+    }
+
     switch (code) {
         case SET_DEVICE_CONNECTION_STATE: {
             CHECK_INTERFACE(IAudioPolicyService, data, reply);