Handle GET_POWER failures

Return a failure when GET_POWER returns a non-conforming
format

Bug: 4380317
Change-Id: If1ce73572ae261cd6998e4289e21112c88859437

core/jni/android_net_wifi_Wifi.cpp

@@ -402,7 +402,9 @@ static jint android_net_wifi_getPowerModeCommand(JNIEnv* env, jobject clazz)
     }
     // reply comes back in the form "powermode = XX" where XX is the
     // number we're interested in.
-    sscanf(reply, "%*s = %u", &power);
+    if (sscanf(reply, "%*s = %u", &power) != 1) {
+        return (jint)-1;
+    }
     return (jint)power;
 }