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Remove local stack variable form MPU wrappers

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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>
This commit is contained in:
Gaurav Aggarwal 2022-09-07 19:49:48 +05:30 committed by Gaurav-Aggarwal-AWS
parent c4ad77f694
commit 51ea2bfe62
7 changed files with 1642 additions and 497 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
.github/lexicon.txt vendored
View file

@ -2533,7 +2533,6 @@ vportgetheapstats
vportinitialiseblocks
vportisrstartfirststask
vportraisebasepri
vportresetprivilege
vportsetmpuregistersetone
vportsetuptimerinterrupt
vportstartfirststask
@ -2852,7 +2851,6 @@ xperiod
xportgetcoreid
xportgetfreeheapsize
xportinstallinterrupthandler
xportraiseprivilege
xportregistercinterrupthandler
xportregisterdump
xportstartfirsttask

30
include/mpu_wrappers.h
View file

@ -170,36 +170,6 @@
#define PRIVILEGED_DATA __attribute__( ( section( "privileged_data" ) ) )
#define FREERTOS_SYSTEM_CALL __attribute__( ( section( "freertos_system_calls" ) ) )
/**
* @brief Calls the port specific code to raise the privilege.
*
* Sets xRunningPrivileged to pdFALSE if privilege was raised, else sets
* it to pdTRUE.
*/
#define xPortRaisePrivilege( xRunningPrivileged ) \
{ \
/* Check whether the processor is already privileged. */ \
xRunningPrivileged = portIS_PRIVILEGED(); \
\
/* If the processor is not already privileged, raise privilege. */ \
if( xRunningPrivileged == pdFALSE ) \
{ \
portRAISE_PRIVILEGE(); \
} \
}
/**
* @brief If xRunningPrivileged is not pdTRUE, calls the port specific
* code to reset the privilege, otherwise does nothing.
*/
#define vPortResetPrivilege( xRunningPrivileged ) \
{ \
if( xRunningPrivileged == pdFALSE ) \
{ \
portRESET_PRIVILEGE(); \
} \
}
#endif /* MPU_WRAPPERS_INCLUDED_FROM_API_FILE */
#else /* portUSING_MPU_WRAPPERS */

1858
portable/Common/mpu_wrappers.c
View file

File diff suppressed because it is too large Load diff

55
portable/GCC/ARM_CM3_MPU/port.c
View file

@ -478,30 +478,55 @@ void vPortEndScheduler( void )
void vPortEnterCritical( void )
{
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
if( portIS_PRIVILEGED() == pdFALSE )
{
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
portMEMORY_BARRIER();
vPortResetPrivilege( xRunningPrivileged );
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
}
}
/*-----------------------------------------------------------*/
void vPortExitCritical( void )
{
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
if( portIS_PRIVILEGED() == pdFALSE )
{
portENABLE_INTERRUPTS();
}
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
vPortResetPrivilege( xRunningPrivileged );
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
portMEMORY_BARRIER();
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
}
}
/*-----------------------------------------------------------*/

55
portable/GCC/ARM_CM4_MPU/port.c
View file

@ -514,30 +514,55 @@ void vPortEndScheduler( void )
void vPortEnterCritical( void )
{
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
if( portIS_PRIVILEGED() == pdFALSE )
{
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
portMEMORY_BARRIER();
vPortResetPrivilege( xRunningPrivileged );
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
}
}
/*-----------------------------------------------------------*/
void vPortExitCritical( void )
{
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
if( portIS_PRIVILEGED() == pdFALSE )
{
portENABLE_INTERRUPTS();
}
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
vPortResetPrivilege( xRunningPrivileged );
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
portMEMORY_BARRIER();
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
}
}
/*-----------------------------------------------------------*/

84
portable/IAR/ARM_CM4F_MPU/port.c
View file

@ -442,41 +442,73 @@ void vPortEndScheduler( void )
void vPortEnterCritical( void )
{
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
/* This is not the interrupt safe version of the enter critical function so
* assert() if it is being called from an interrupt context. Only API
* functions that end in "FromISR" can be used in an interrupt. Only assert if
* the critical nesting count is 1 to protect against recursive calls if the
* assert function also uses a critical section. */
if( uxCriticalNesting == 1 )
if( portIS_PRIVILEGED() == pdFALSE )
{
configASSERT( ( portNVIC_INT_CTRL_REG & portVECTACTIVE_MASK ) == 0 );
}
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
vPortResetPrivilege( xRunningPrivileged );
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
/* This is not the interrupt safe version of the enter critical function so
* assert() if it is being called from an interrupt context. Only API
* functions that end in "FromISR" can be used in an interrupt. Only assert if
* the critical nesting count is 1 to protect against recursive calls if the
* assert function also uses a critical section. */
if( uxCriticalNesting == 1 )
{
configASSERT( ( portNVIC_INT_CTRL_REG & portVECTACTIVE_MASK ) == 0 );
}
portMEMORY_BARRIER();
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
/* This is not the interrupt safe version of the enter critical function so
* assert() if it is being called from an interrupt context. Only API
* functions that end in "FromISR" can be used in an interrupt. Only assert if
* the critical nesting count is 1 to protect against recursive calls if the
* assert function also uses a critical section. */
if( uxCriticalNesting == 1 )
{
configASSERT( ( portNVIC_INT_CTRL_REG & portVECTACTIVE_MASK ) == 0 );
}
}
}
/*-----------------------------------------------------------*/
void vPortExitCritical( void )
{
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
if( portIS_PRIVILEGED() == pdFALSE )
{
portENABLE_INTERRUPTS();
}
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
vPortResetPrivilege( xRunningPrivileged );
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
portMEMORY_BARRIER();
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
}
}
/*-----------------------------------------------------------*/

55
portable/RVDS/ARM_CM4_MPU/port.c
View file

@ -517,30 +517,55 @@ void vPortEndScheduler( void )
void vPortEnterCritical( void )
{
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
if( portIS_PRIVILEGED() == pdFALSE )
{
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
portMEMORY_BARRIER();
vPortResetPrivilege( xRunningPrivileged );
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
}
}
/*-----------------------------------------------------------*/
void vPortExitCritical( void )
{
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
if( portIS_PRIVILEGED() == pdFALSE )
{
portENABLE_INTERRUPTS();
}
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
vPortResetPrivilege( xRunningPrivileged );
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
portMEMORY_BARRIER();
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
}
}
/*-----------------------------------------------------------*/