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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 14:57:37 +05:30 committed by Gaurav-Aggarwal-AWS
parent c2d616eaee
commit 79704b8213
7 changed files with 1693 additions and 490 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
.github/lexicon.txt vendored
View file

@ -2547,7 +2547,6 @@ vportgetheapstats
vportinitialiseblocks
vportisrstartfirststask
vportraisebasepri
vportresetprivilege
vportsetmpuregistersetone
vportsetuptimerinterrupt
vportstartfirststask
@ -2872,7 +2871,6 @@ xperiod
xportgetcoreid
xportgetfreeheapsize
xportinstallinterrupthandler
xportraiseprivilege
xportregistercinterrupthandler
xportregisterdump
xportstartfirsttask

30
include/mpu_wrappers.h
View file

@ -173,36 +173,6 @@
#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 */

1907
portable/Common/mpu_wrappers.c
View file

File diff suppressed because it is too large Load diff

56
portable/GCC/ARM_CM3_MPU/port.c
View file

@ -495,15 +495,26 @@ void vPortEndScheduler( void )
void vPortEnterCritical( void )
{
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
#endif
if( portIS_PRIVILEGED() == pdFALSE )
{
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
portMEMORY_BARRIER();
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
}
#else
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
vPortResetPrivilege( xRunningPrivileged );
#endif
}
/*-----------------------------------------------------------*/
@ -511,10 +522,34 @@ void vPortEnterCritical( void )
void vPortExitCritical( void )
{
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
#endif
if( portIS_PRIVILEGED() == pdFALSE )
{
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
portMEMORY_BARRIER();
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
}
#else
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
@ -522,9 +557,6 @@ void vPortExitCritical( void )
{
portENABLE_INTERRUPTS();
}
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
vPortResetPrivilege( xRunningPrivileged );
#endif
}
/*-----------------------------------------------------------*/

56
portable/GCC/ARM_CM4_MPU/port.c
View file

@ -549,15 +549,26 @@ void vPortEndScheduler( void )
void vPortEnterCritical( void )
{
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
#endif
if( portIS_PRIVILEGED() == pdFALSE )
{
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
portMEMORY_BARRIER();
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
}
#else
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
vPortResetPrivilege( xRunningPrivileged );
#endif
}
/*-----------------------------------------------------------*/
@ -565,10 +576,34 @@ void vPortEnterCritical( void )
void vPortExitCritical( void )
{
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
#endif
if( portIS_PRIVILEGED() == pdFALSE )
{
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
portMEMORY_BARRIER();
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
}
#else
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
@ -576,9 +611,6 @@ void vPortExitCritical( void )
{
portENABLE_INTERRUPTS();
}
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
vPortResetPrivilege( xRunningPrivileged );
#endif
}
/*-----------------------------------------------------------*/

76
portable/IAR/ARM_CM4F_MPU/port.c
View file

@ -464,13 +464,44 @@ void vPortEndScheduler( void )
void vPortEnterCritical( void )
{
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
#endif
if( portIS_PRIVILEGED() == pdFALSE )
{
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
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 );
}
}
#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
@ -480,9 +511,6 @@ void vPortEnterCritical( void )
{
configASSERT( ( portNVIC_INT_CTRL_REG & portVECTACTIVE_MASK ) == 0 );
}
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
vPortResetPrivilege( xRunningPrivileged );
#endif
}
/*-----------------------------------------------------------*/
@ -490,21 +518,41 @@ void vPortEnterCritical( void )
void vPortExitCritical( void )
{
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
#endif
if( portIS_PRIVILEGED() == pdFALSE )
{
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
portMEMORY_BARRIER();
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
}
#else
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
vPortResetPrivilege( xRunningPrivileged );
#endif
}
/*-----------------------------------------------------------*/

56
portable/RVDS/ARM_CM4_MPU/port.c
View file

@ -551,15 +551,26 @@ void vPortEndScheduler( void )
void vPortEnterCritical( void )
{
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
#endif
if( portIS_PRIVILEGED() == pdFALSE )
{
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
portMEMORY_BARRIER();
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
}
#else
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
vPortResetPrivilege( xRunningPrivileged );
#endif
}
/*-----------------------------------------------------------*/
@ -567,10 +578,34 @@ void vPortEnterCritical( void )
void vPortExitCritical( void )
{
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
BaseType_t xRunningPrivileged;
xPortRaisePrivilege( xRunningPrivileged );
#endif
if( portIS_PRIVILEGED() == pdFALSE )
{
portRAISE_PRIVILEGE();
portMEMORY_BARRIER();
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
portMEMORY_BARRIER();
portRESET_PRIVILEGE();
portMEMORY_BARRIER();
}
else
{
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
}
#else
configASSERT( uxCriticalNesting );
uxCriticalNesting--;
@ -578,9 +613,6 @@ void vPortExitCritical( void )
{
portENABLE_INTERRUPTS();
}
#if( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 )
vPortResetPrivilege( xRunningPrivileged );
#endif
}
/*-----------------------------------------------------------*/