Restrict unpriv task to invoke code with privilege

It was possible for an unprivileged task to invoke any function with
privilege by passing it as a parameter to MPU_xTaskCreate,
MPU_xTaskCreateStatic, MPU_xTimerCreate, MPU_xTimerCreateStatic, or
MPU_xTimerPendFunctionCall.

This commit ensures that MPU_xTaskCreate and MPU_xTaskCreateStatic can
only create unprivileged tasks. It also removes the following APIs:
1. MPU_xTimerCreate
2. MPU_xTimerCreateStatic
3. MPU_xTimerPendFunctionCall

We thank Huazhong University of Science and Technology for reporting
this issue.

Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>

Author: aggarg

include/mpu_wrappers.h

@@ -120,13 +120,10 @@
         #endif
 
 /* Map standard timer.h API functions to the MPU equivalents. */
-        #define xTimerCreate                           MPU_xTimerCreate
-        #define xTimerCreateStatic                     MPU_xTimerCreateStatic
         #define pvTimerGetTimerID                      MPU_pvTimerGetTimerID
         #define vTimerSetTimerID                       MPU_vTimerSetTimerID
         #define xTimerIsTimerActive                    MPU_xTimerIsTimerActive
         #define xTimerGetTimerDaemonTaskHandle         MPU_xTimerGetTimerDaemonTaskHandle
-        #define xTimerPendFunctionCall                 MPU_xTimerPendFunctionCall
         #define pcTimerGetName                         MPU_pcTimerGetName
         #define vTimerSetReloadMode                    MPU_vTimerSetReloadMode
         #define uxTimerGetReloadMode                   MPU_uxTimerGetReloadMode

portable/Common/mpu_wrappers.c

@@ -65,6 +65,9 @@
                 portRAISE_PRIVILEGE();
                 portMEMORY_BARRIER();
 
+                uxPriority = uxPriority & ~( portPRIVILEGE_BIT );
+                portMEMORY_BARRIER();
+
                 xReturn = xTaskCreate( pvTaskCode, pcName, usStackDepth, pvParameters, uxPriority, pxCreatedTask );
                 portMEMORY_BARRIER();
 
@@ -97,6 +100,9 @@
                 portRAISE_PRIVILEGE();
                 portMEMORY_BARRIER();
 
+                uxPriority = uxPriority & ~( portPRIVILEGE_BIT );
+                portMEMORY_BARRIER();
+
                 xReturn = xTaskCreateStatic( pxTaskCode, pcName, ulStackDepth, pvParameters, uxPriority, puxStackBuffer, pxTaskBuffer );
                 portMEMORY_BARRIER();
 
@@ -1708,67 +1714,6 @@
     }
 /*-----------------------------------------------------------*/
 
-    #if ( ( configSUPPORT_DYNAMIC_ALLOCATION == 1 ) && ( configUSE_TIMERS == 1 ) )
-        TimerHandle_t MPU_xTimerCreate( const char * const pcTimerName,
-                                        const TickType_t xTimerPeriodInTicks,
-                                        const UBaseType_t uxAutoReload,
-                                        void * const pvTimerID,
-                                        TimerCallbackFunction_t pxCallbackFunction ) /* FREERTOS_SYSTEM_CALL */
-        {
-            TimerHandle_t xReturn;
-
-            if( portIS_PRIVILEGED() == pdFALSE )
-            {
-                portRAISE_PRIVILEGE();
-                portMEMORY_BARRIER();
-
-                xReturn = xTimerCreate( pcTimerName, xTimerPeriodInTicks, uxAutoReload, pvTimerID, pxCallbackFunction );
-                portMEMORY_BARRIER();
-
-                portRESET_PRIVILEGE();
-                portMEMORY_BARRIER();
-            }
-            else
-            {
-                xReturn = xTimerCreate( pcTimerName, xTimerPeriodInTicks, uxAutoReload, pvTimerID, pxCallbackFunction );
-            }
-
-            return xReturn;
-        }
-    #endif /* if ( ( configSUPPORT_DYNAMIC_ALLOCATION == 1 ) && ( configUSE_TIMERS == 1 ) ) */
-/*-----------------------------------------------------------*/
-
-    #if ( ( configSUPPORT_STATIC_ALLOCATION == 1 ) && ( configUSE_TIMERS == 1 ) )
-        TimerHandle_t MPU_xTimerCreateStatic( const char * const pcTimerName,
-                                              const TickType_t xTimerPeriodInTicks,
-                                              const UBaseType_t uxAutoReload,
-                                              void * const pvTimerID,
-                                              TimerCallbackFunction_t pxCallbackFunction,
-                                              StaticTimer_t * pxTimerBuffer ) /* FREERTOS_SYSTEM_CALL */
-        {
-            TimerHandle_t xReturn;
-
-            if( portIS_PRIVILEGED() == pdFALSE )
-            {
-                portRAISE_PRIVILEGE();
-                portMEMORY_BARRIER();
-
-                xReturn = xTimerCreateStatic( pcTimerName, xTimerPeriodInTicks, uxAutoReload, pvTimerID, pxCallbackFunction, pxTimerBuffer );
-                portMEMORY_BARRIER();
-
-                portRESET_PRIVILEGE();
-                portMEMORY_BARRIER();
-            }
-            else
-            {
-                xReturn = xTimerCreateStatic( pcTimerName, xTimerPeriodInTicks, uxAutoReload, pvTimerID, pxCallbackFunction, pxTimerBuffer );
-            }
-
-            return xReturn;
-        }
-    #endif /* if ( ( configSUPPORT_STATIC_ALLOCATION == 1 ) && ( configUSE_TIMERS == 1 ) ) */
-/*-----------------------------------------------------------*/
-
     #if ( configUSE_TIMERS == 1 )
         void * MPU_pvTimerGetTimerID( const TimerHandle_t xTimer ) /* FREERTOS_SYSTEM_CALL */
         {
@@ -1870,35 +1815,6 @@
     #endif /* if ( configUSE_TIMERS == 1 ) */
 /*-----------------------------------------------------------*/
 
-    #if ( ( INCLUDE_xTimerPendFunctionCall == 1 ) && ( configUSE_TIMERS == 1 ) )
-        BaseType_t MPU_xTimerPendFunctionCall( PendedFunction_t xFunctionToPend,
-                                               void * pvParameter1,
-                                               uint32_t ulParameter2,
-                                               TickType_t xTicksToWait ) /* FREERTOS_SYSTEM_CALL */
-        {
-            BaseType_t xReturn;
-
-            if( portIS_PRIVILEGED() == pdFALSE )
-            {
-                portRAISE_PRIVILEGE();
-                portMEMORY_BARRIER();
-
-                xReturn = xTimerPendFunctionCall( xFunctionToPend, pvParameter1, ulParameter2, xTicksToWait );
-                portMEMORY_BARRIER();
-
-                portRESET_PRIVILEGE();
-                portMEMORY_BARRIER();
-            }
-            else
-            {
-                xReturn = xTimerPendFunctionCall( xFunctionToPend, pvParameter1, ulParameter2, xTicksToWait );
-            }
-
-            return xReturn;
-        }
-    #endif /* if ( ( INCLUDE_xTimerPendFunctionCall == 1 ) && ( configUSE_TIMERS == 1 ) ) */
-/*-----------------------------------------------------------*/
-
     #if ( configUSE_TIMERS == 1 )
         void MPU_vTimerSetReloadMode( TimerHandle_t xTimer,
                                       const UBaseType_t uxAutoReload ) /* FREERTOS_SYSTEM_CALL */