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>
It was possible for a third party that had already independently gained
the ability to execute injected code to achieve further privilege
escalation by branching directly inside a FreeRTOS MPU API wrapper
function with a manually crafted stack frame. This commit removes the
local stack variable `xRunningPrivileged` so that a manually crafted
stack frame cannot be used for privilege escalation by branching
directly inside a FreeRTOS MPU API wrapper.
We thank Certibit Consulting, LLC, Huazhong University of Science and
Technology and the SecLab team at Northeastern University for reporting
this issue.
Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>
The secure side context management code now checks that the secure
context being saved or restored belongs to the task being switched-out
or switched-in respectively.
Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>
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 PR:
Changes the INCLUDE_vTaskDelayUntil compile time constant to INCLUDE_xTaskDelayUntil.
Updates FreeRTOS.h to ensure backward compatibility for projects that already have INCLUDE_vTaskDelayUntil defined.
Updates the MPU prototypes, wrapper and implementation to use the updated xTaskDelayUntil() function.
Tests to be checked into the FreeRTOS/FreeRTOS repository after this PR.
* Style: Change FreeRTOS websites in comments
* Style: Change freertos to FreeRTOS in comments
* Style: Remove broken link
Co-authored-by: Alfred Gedeon <gedeonag@amazon.com>
The expected behaviour of portIS_PRIVILEGED is:
- return 0 if the processor is not running privileged.
- return 1 if the processor is running privileged.
Some TI ports do not return 1 when the processor is running privileged
causing the following check to fail: if( xRunningPrivileged != pdTRUE )
This commit change the check to: if( xRunningPrivileged == pdFALSE ). It
ensures that the check is successful even on the ports which return incorrect
value from portIS_PRIVILEGED when the processor is running privileged.
See https://forums.freertos.org/t/kernel-bug-nested-mpu-wrapper-calls-generate-an-exception/10391
Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>
These definitions were not useful because the corresponding mapping was
removed from mpu_wrappers.h earlier.
Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>
