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Disallow unprivileged critical sections with MPU wrappers v2 (#1427)
When using MPU wrappers version 2 (configUSE_MPU_WRAPPERS_V1 == 0), portRAISE_PRIVILEGE() is a no-op because the portSVC_RAISE_PRIVILEGE handler is compiled only for MPU wrappers version 1. As a result, an unprivileged task that calls taskENTER_CRITICAL() does not actually raise its privilege, so the subsequent BASEPRI write is ignored by the hardware and the critical section silently fails to mask interrupts. This produces latent, hard-to-debug faults. configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is therefore not supported with MPU wrappers version 2. In the ARMv7-M MPU ports: - When the option is left undefined under v2, default it to 0 instead of 1 so the dangerous default configuration is safe. - When the option is explicitly set to 1 under v2, raise a compile-time #error so the unsupported configuration is rejected loudly rather than failing silently at run time. Behaviour for MPU wrappers version 1 is unchanged.
1 parent fc25364 commit 83e56c3

4 files changed

Lines changed: 48 additions & 8 deletions

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‎portable/GCC/ARM_CM3_MPU/port.c‎

Lines changed: 12 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -55,9 +55,19 @@
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#define portNVIC_SYSTICK_CLK ( 0 )
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#endif
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58+
/* Unprivileged critical sections are not supported when using MPU wrappers
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* version 2. Default the option to 0 and reject an explicit value of 1. */
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#ifndef configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS
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#warning "configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not defined. We recommend defining it to 0 in FreeRTOSConfig.h for better security."
60-
#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 1
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#if ( configUSE_MPU_WRAPPERS_V1 == 0 )
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#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 0
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#else
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#warning "configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not defined. We recommend defining it to 0 in FreeRTOSConfig.h for better security."
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#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 1
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#endif
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#else
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#if ( ( configUSE_MPU_WRAPPERS_V1 == 0 ) && ( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 ) )
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#error configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not supported with MPU wrappers version 2 ( configUSE_MPU_WRAPPERS_V1 == 0 ).
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#endif
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#endif
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/* Prototype of all Interrupt Service Routines (ISRs). */

‎portable/GCC/ARM_CM4_MPU/port.c‎

Lines changed: 12 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -59,9 +59,19 @@
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#define portNVIC_SYSTICK_CLK ( 0 )
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#endif
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/* Unprivileged critical sections are not supported when using MPU wrappers
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* version 2. Default the option to 0 and reject an explicit value of 1. */
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#ifndef configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS
63-
#warning "configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not defined. We recommend defining it to 0 in FreeRTOSConfig.h for better security."
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#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 1
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#if ( configUSE_MPU_WRAPPERS_V1 == 0 )
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#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 0
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#else
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#warning "configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not defined. We recommend defining it to 0 in FreeRTOSConfig.h for better security."
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#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 1
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#endif
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#else
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#if ( ( configUSE_MPU_WRAPPERS_V1 == 0 ) && ( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 ) )
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#error configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not supported with MPU wrappers version 2 ( configUSE_MPU_WRAPPERS_V1 == 0 ).
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#endif
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#endif
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/* Prototype of all Interrupt Service Routines (ISRs). */

‎portable/IAR/ARM_CM4F_MPU/port.c‎

Lines changed: 12 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -66,9 +66,19 @@
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#define portNVIC_SYSTICK_CLK_BIT ( 0 )
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#endif
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/* Unprivileged critical sections are not supported when using MPU wrappers
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* version 2. Default the option to 0 and reject an explicit value of 1. */
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#ifndef configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS
70-
#warning "configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not defined. We recommend defining it to 0 in FreeRTOSConfig.h for better security."
71-
#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 1
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#if ( configUSE_MPU_WRAPPERS_V1 == 0 )
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#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 0
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#else
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#warning "configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not defined. We recommend defining it to 0 in FreeRTOSConfig.h for better security."
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#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 1
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#endif
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#else
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#if ( ( configUSE_MPU_WRAPPERS_V1 == 0 ) && ( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 ) )
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#error configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not supported with MPU wrappers version 2 ( configUSE_MPU_WRAPPERS_V1 == 0 ).
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#endif
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#endif
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/* Prototype of all Interrupt Service Routines (ISRs). */

‎portable/RVDS/ARM_CM4_MPU/port.c‎

Lines changed: 12 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -48,9 +48,19 @@
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#undef MPU_WRAPPERS_INCLUDED_FROM_API_FILE
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51+
/* Unprivileged critical sections are not supported when using MPU wrappers
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* version 2. Default the option to 0 and reject an explicit value of 1. */
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#ifndef configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS
52-
#warning "configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not defined. We recommend defining it to 0 in FreeRTOSConfig.h for better security."
53-
#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 1
54+
#if ( configUSE_MPU_WRAPPERS_V1 == 0 )
55+
#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 0
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#else
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#warning "configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not defined. We recommend defining it to 0 in FreeRTOSConfig.h for better security."
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#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS 1
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#endif
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#else
61+
#if ( ( configUSE_MPU_WRAPPERS_V1 == 0 ) && ( configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS == 1 ) )
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#error configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS is not supported with MPU wrappers version 2 ( configUSE_MPU_WRAPPERS_V1 == 0 ).
63+
#endif
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#endif
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/* Prototype of all Interrupt Service Routines (ISRs). */

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