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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
3 changed files with 0 additions and 46 deletions
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6
include/mpu_prototypes.h
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@ -50,12 +50,6 @@ TaskHandle_t MPU_xTaskCreateStatic( TaskFunction_t pxTaskCode,
UBaseType_t uxPriority,
StackType_t * const puxStackBuffer,
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_vTaskDelay( const TickType_t xTicksToDelay ) FREERTOS_SYSTEM_CALL;
BaseType_t MPU_xTaskDelayUntil( TickType_t * const pxPreviousWakeTime,