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Prevent unprivileged task from altering MPU configuration (#227)

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This change removes the FreeRTOS System Calls (aka MPU wrappers) for the
following kernel APIs:
- xTaskCreateRestricted
- xTaskCreateRestrictedStatic
- vTaskAllocateMPURegions

A system call allows an unprivileged task to execute a kernel API which
is otherwise accessible to privileged software only. The above 3 APIs
can create a new task with a different MPU configuration or alter the
MPU configuration of an existing task. This an be (mis)used by an
unprivileged task to grant itself access to a region which it does not
have access to.

Removing the system calls for these APIs ensures that an unprivileged
task cannot execute this APIs. If an unprivileged task attempts to
execute any of these API, it will result in a Memory Fault.

Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>
This commit is contained in:
Gaurav-Aggarwal-AWS 2020-12-07 09:53:22 -08:00 committed by GitHub
parent 68ca3a9b2a
commit b5020cb3d8
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 0 additions and 46 deletions
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6
include/mpu_prototypes.h
View File

@ -50,12 +50,6 @@ TaskHandle_t MPU_xTaskCreateStatic( TaskFunction_t pxTaskCode,
UBaseType_t uxPriority, UBaseType_t uxPriority,
StackType_t * const puxStackBuffer, StackType_t * const puxStackBuffer,
StaticTask_t * const pxTaskBuffer ) FREERTOS_SYSTEM_CALL; StaticTask_t * const pxTaskBuffer ) FREERTOS_SYSTEM_CALL;
BaseType_t MPU_xTaskCreateRestricted( const TaskParameters_t * const pxTaskDefinition,
TaskHandle_t * pxCreatedTask ) FREERTOS_SYSTEM_CALL;
BaseType_t MPU_xTaskCreateRestrictedStatic( const TaskParameters_t * const pxTaskDefinition,
TaskHandle_t * pxCreatedTask ) FREERTOS_SYSTEM_CALL;
void MPU_vTaskAllocateMPURegions( TaskHandle_t xTask,
const MemoryRegion_t * const pxRegions ) FREERTOS_SYSTEM_CALL;
void MPU_vTaskDelete( TaskHandle_t xTaskToDelete ) FREERTOS_SYSTEM_CALL; void MPU_vTaskDelete( TaskHandle_t xTaskToDelete ) FREERTOS_SYSTEM_CALL;
void MPU_vTaskDelay( const TickType_t xTicksToDelay ) FREERTOS_SYSTEM_CALL; void MPU_vTaskDelay( const TickType_t xTicksToDelay ) FREERTOS_SYSTEM_CALL;
BaseType_t MPU_xTaskDelayUntil( TickType_t * const pxPreviousWakeTime, BaseType_t MPU_xTaskDelayUntil( TickType_t * const pxPreviousWakeTime,

2
include/mpu_wrappers.h
View File

@ -47,8 +47,6 @@
/* Map standard tasks.h API functions to the MPU equivalents. */ /* Map standard tasks.h API functions to the MPU equivalents. */
#define xTaskCreate MPU_xTaskCreate #define xTaskCreate MPU_xTaskCreate
#define xTaskCreateStatic MPU_xTaskCreateStatic #define xTaskCreateStatic MPU_xTaskCreateStatic
#define xTaskCreateRestricted MPU_xTaskCreateRestricted
#define vTaskAllocateMPURegions MPU_vTaskAllocateMPURegions
#define vTaskDelete MPU_vTaskDelete #define vTaskDelete MPU_vTaskDelete
#define vTaskDelay MPU_vTaskDelay #define vTaskDelay MPU_vTaskDelay
#define xTaskDelayUntil MPU_xTaskDelayUntil #define xTaskDelayUntil MPU_xTaskDelayUntil

38
portable/Common/mpu_wrappers.c
View File

@ -85,34 +85,6 @@ void vPortResetPrivilege( BaseType_t xRunningPrivileged )
} }
/*-----------------------------------------------------------*/ /*-----------------------------------------------------------*/
#if ( configSUPPORT_DYNAMIC_ALLOCATION == 1 )
BaseType_t MPU_xTaskCreateRestricted( const TaskParameters_t * const pxTaskDefinition,
TaskHandle_t * pxCreatedTask ) /* FREERTOS_SYSTEM_CALL */
{
BaseType_t xReturn;
BaseType_t xRunningPrivileged = xPortRaisePrivilege();
xReturn = xTaskCreateRestricted( pxTaskDefinition, pxCreatedTask );
vPortResetPrivilege( xRunningPrivileged );
return xReturn;
}
#endif /* conifgSUPPORT_DYNAMIC_ALLOCATION */
/*-----------------------------------------------------------*/
#if ( configSUPPORT_STATIC_ALLOCATION == 1 )
BaseType_t MPU_xTaskCreateRestrictedStatic( const TaskParameters_t * const pxTaskDefinition,
TaskHandle_t * pxCreatedTask ) /* FREERTOS_SYSTEM_CALL */
{
BaseType_t xReturn;
BaseType_t xRunningPrivileged = xPortRaisePrivilege();
xReturn = xTaskCreateRestrictedStatic( pxTaskDefinition, pxCreatedTask );
vPortResetPrivilege( xRunningPrivileged );
return xReturn;
}
#endif /* conifgSUPPORT_DYNAMIC_ALLOCATION */
/*-----------------------------------------------------------*/
#if ( configSUPPORT_DYNAMIC_ALLOCATION == 1 ) #if ( configSUPPORT_DYNAMIC_ALLOCATION == 1 )
BaseType_t MPU_xTaskCreate( TaskFunction_t pvTaskCode, BaseType_t MPU_xTaskCreate( TaskFunction_t pvTaskCode,
const char * const pcName, const char * const pcName,
@ -150,16 +122,6 @@ void vPortResetPrivilege( BaseType_t xRunningPrivileged )
#endif /* configSUPPORT_STATIC_ALLOCATION */ #endif /* configSUPPORT_STATIC_ALLOCATION */
/*-----------------------------------------------------------*/ /*-----------------------------------------------------------*/
void MPU_vTaskAllocateMPURegions( TaskHandle_t xTask,
const MemoryRegion_t * const xRegions ) /* FREERTOS_SYSTEM_CALL */
{
BaseType_t xRunningPrivileged = xPortRaisePrivilege();
vTaskAllocateMPURegions( xTask, xRegions );
vPortResetPrivilege( xRunningPrivileged );
}
/*-----------------------------------------------------------*/
#if ( INCLUDE_vTaskDelete == 1 ) #if ( INCLUDE_vTaskDelete == 1 )
void MPU_vTaskDelete( TaskHandle_t pxTaskToDelete ) /* FREERTOS_SYSTEM_CALL */ void MPU_vTaskDelete( TaskHandle_t pxTaskToDelete ) /* FREERTOS_SYSTEM_CALL */
{ {