Based on a change recommended by Mark Shulte:

Signal handlers maybe run with interrupts enabled or disabled, depending on how the task the received the signal was blocked. (i.e.: If sem_wait() is called, then we disable interrupts, then block the currently running task). This could be dangerous, because user code would be running with interrupts disabled.

This change forces interrupts to be enabled in up_sigdeliver() before executing the signal handler calling up_irq_enable() explicitly.  This is safe because, when we return to normal execution, interrupts will be restored to their previous state when the signal handler returns.

arch/arm/include/armv7-m/irq.h

@@ -292,7 +292,7 @@ static inline irqstate_t up_irq_save(void)
 static inline void up_irq_enable(void) inline_function;
 static inline void up_irq_enable(void)
 {
-  setbasepri(0);
+  setbasepri(NVIC_SYSH_PRIORITY_MIN);
   __asm__ __volatile__ ("\tcpsie  i\n");
 }
 

arch/arm/src/arm/up_sigdeliver.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/arm/src/arm/up_sigdeliver.c
  *
- *   Copyright (C) 2007-2010, 2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2010, 2015, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <[email protected]>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -113,9 +113,13 @@ void up_sigdeliver(void)
   sigdeliver           = rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
-  /* Then restore the task interrupt state */
+#ifndef CONFIG_SUPPRESS_INTERRUPTS
+  /* Then make sure that interrupts are enabled.  Signal handlers must always
+   * run with interrupts enabled.
+   */
 
-  up_irq_restore(regs[REG_CPSR]);
+  up_irq_enable();
+#endif
 
   /* Deliver the signals */
 

arch/arm/src/armv6-m/up_sigdeliver.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/arm/src/armv6-m/up_sigdeliver.c
  *
- *   Copyright (C) 2013-2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2013-2015, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <[email protected]>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -54,18 +54,6 @@
 
 #ifndef CONFIG_DISABLE_SIGNALS
 
-/****************************************************************************
- * Pre-processor Definitions
- ****************************************************************************/
-
-/****************************************************************************
- * Private Data
- ****************************************************************************/
-
-/****************************************************************************
- * Private Functions
- ****************************************************************************/
-
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -122,9 +110,13 @@ void up_sigdeliver(void)
   sigdeliver           = rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
-  /* Then restore the task interrupt state */
+#ifndef CONFIG_SUPPRESS_INTERRUPTS
+  /* Then make sure that interrupts are enabled.  Signal handlers must always
+   * run with interrupts enabled.
+   */
 
-  up_irq_restore((uint8_t)regs[REG_PRIMASK]);
+  up_irq_enable();
+#endif
 
   /* Deliver the signal */
 

arch/arm/src/armv7-a/arm_sigdeliver.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/arm/src/armv7-a/arm_sigdeliver.c
  *
- *   Copyright (C) 2013, 2015-2016 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2013, 2015-2016, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <[email protected]>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -101,9 +101,13 @@ void up_sigdeliver(void)
   sigdeliver           = rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
-  /* Then restore the task interrupt state */
+#ifndef CONFIG_SUPPRESS_INTERRUPTS
+  /* Then make sure that interrupts are enabled.  Signal handlers must always
+   * run with interrupts enabled.
+   */
 
-  leave_critical_section(regs[REG_CPSR]);
+  up_irq_enable();
+#endif
 
   /* Deliver the signal */
 

arch/arm/src/armv7-m/up_sigdeliver.c

@@ -1,7 +1,8 @@
 /****************************************************************************
  * arch/arm/src/armv7-m/up_sigdeliver.c
  *
- *   Copyright (C) 2009-2010, 2013-2016 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2009-2010, 2013-2016, 2018 Gregory Nutt. All rights
+ *     reserved.
  *   Author: Gregory Nutt <[email protected]>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -109,12 +110,12 @@ void up_sigdeliver(void)
   sigdeliver           = (sig_deliver_t)rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
-  /* Then restore the task interrupt state */
+#ifndef CONFIG_SUPPRESS_INTERRUPTS
+  /* Then make sure that interrupts are enabled.  Signal handlers must always
+   * run with interrupts enabled.
+   */
 
-#ifdef CONFIG_ARMV7M_USEBASEPRI
-  leave_critical_section((uint8_t)regs[REG_BASEPRI]);
-#else
-  leave_critical_section((uint16_t)regs[REG_PRIMASK]);
+  up_irq_enable();
 #endif
 
   /* Deliver the signal */

arch/arm/src/armv7-r/arm_sigdeliver.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/arm/src/armv7-r/arm_sigdeliver.c
  *
- *   Copyright (C) 2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2015, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <[email protected]>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -101,9 +101,13 @@ void up_sigdeliver(void)
   sigdeliver           = rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
-  /* Then restore the task interrupt state */
+#ifndef CONFIG_SUPPRESS_INTERRUPTS
+  /* Then make sure that interrupts are enabled.  Signal handlers must always
+   * run with interrupts enabled.
+   */
 
-  up_irq_restore(regs[REG_CPSR]);
+  up_irq_enable();
+#endif
 
   /* Deliver the signals */
 

arch/avr/src/avr/up_sigdeliver.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/avr/src/avr/up_sigdeliver.c
  *
- *   Copyright (C) 2011, 2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2011, 2015, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <[email protected]>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -104,9 +104,13 @@ void up_sigdeliver(void)
   sigdeliver           = rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
-  /* Then restore the task interrupt state */
+#ifndef CONFIG_SUPPRESS_INTERRUPTS
+  /* Then make sure that interrupts are enabled.  Signal handlers must always
+   * run with interrupts enabled.
+   */
 
-  up_irq_restore(regs[REG_SREG]);
+  up_irq_enable();
+#endif
 
   /* Deliver the signals */
 

arch/avr/src/avr32/up_sigdeliver.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/avr/src/avr32/up_sigdeliver.c
  *
- *   Copyright (C) 2010, 2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2010, 2015, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <[email protected]>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -104,9 +104,13 @@ void up_sigdeliver(void)
   sigdeliver           = rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
-  /* Then restore the task interrupt state */
+#ifndef CONFIG_SUPPRESS_INTERRUPTS
+  /* Then make sure that interrupts are enabled.  Signal handlers must always
+   * run with interrupts enabled.
+   */
 
-  up_irq_restore(regs[REG_SR]);
+  up_irq_enable();
+#endif
 
   /* Deliver the signals */
 

arch/mips/src/mips32/up_sigdeliver.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/mips/src/mips32/up_sigdeliver.c
  *
- *   Copyright (C) 2011, 2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2011, 2015, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <[email protected]>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -114,9 +114,13 @@ void up_sigdeliver(void)
   sigdeliver           = rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
-  /* Then restore the task interrupt state */
+#ifndef CONFIG_SUPPRESS_INTERRUPTS
+  /* Then make sure that interrupts are enabled.  Signal handlers must always
+   * run with interrupts enabled.
+   */
 
-  up_irq_restore((irqstate_t)regs[REG_STATUS]);
+  up_irq_enable();
+#endif
 
   /* Deliver the signals */
 

arch/misoc/src/lm32/lm32_sigdeliver.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/misoc/src/lm32/lm32_sigdeliver.c
  *
- *   Copyright (C) 2016 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2016, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <[email protected]>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -101,9 +101,13 @@ void lm32_sigdeliver(void)
   sigdeliver           = rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
-  /* Then restore the task interrupt state */
+#ifndef CONFIG_SUPPRESS_INTERRUPTS
+  /* Then make sure that interrupts are enabled.  Signal handlers must always
+   * run with interrupts enabled.
+   */
 
-  up_irq_restore((irqstate_t)regs[REG_INT_CTX]);
+  up_irq_enable();
+#endif
 
   /* Deliver the signals */
 

arch/renesas/src/m16c/m16c_sigdeliver.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/renesas/src/m16c/m16c_sigdeliver.c
  *
- *   Copyright (C) 2009-2010, 2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2009-2010, 2015, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <[email protected]>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -115,9 +115,13 @@ void up_sigdeliver(void)
   sigdeliver           = rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
-  /* Then restore the task interrupt state. */
+#ifndef CONFIG_SUPPRESS_INTERRUPTS
+  /* Then make sure that interrupts are enabled.  Signal handlers must always
+   * run with interrupts enabled.
+   */
 
-  up_irq_restore(rtcb->xcp.saved_flg);
+  up_irq_enable();
+#endif
 
   /* Deliver the signals */
 

arch/renesas/src/sh1/sh1_sigdeliver.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/renesas/src/common/up_sigdeliver.c
  *
- *   Copyright (C) 2008-2010, 2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2010, 2015, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <[email protected]>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -114,9 +114,13 @@ void up_sigdeliver(void)
   sigdeliver           = rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
-  /* Then restore the task interrupt state. */
+#ifndef CONFIG_SUPPRESS_INTERRUPTS
+  /* Then make sure that interrupts are enabled.  Signal handlers must always
+   * run with interrupts enabled.
+   */
 
-  up_irq_restore(regs[REG_SR] & 0x000000f0);
+  up_irq_enable();
+#endif
 
   /* Deliver the signals */
 

arch/risc-v/src/rv32im/up_sigdeliver.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/risc-v/src/rv32im/up_sigdeliver.c
  *
- *   Copyright (C) 2011, 2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2011, 2015, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <[email protected]>
  *
  *   Modified for RISC-V:
@@ -60,18 +60,6 @@
 
 #ifndef CONFIG_DISABLE_SIGNALS
 
-/****************************************************************************
- * Pre-processor Definitions
- ****************************************************************************/
-
-/****************************************************************************
- * Private Data
- ****************************************************************************/
-
-/****************************************************************************
- * Private Functions
- ****************************************************************************/
-
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -119,9 +107,13 @@ void up_sigdeliver(void)
   sigdeliver           = rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
-  /* Then restore the task interrupt state */
+#ifndef CONFIG_SUPPRESS_INTERRUPTS
+  /* Then make sure that interrupts are enabled.  Signal handlers must always
+   * run with interrupts enabled.
+   */
 
-  up_irq_restore((irqstate_t)regs[REG_INT_CTX]);
+  up_irq_enable();
+#endif
 
   /* Deliver the signals */
 

arch/x86/src/i486/up_sigdeliver.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/x86/src/i486/up_sigdeliver.c
  *
- *   Copyright (C) 2011, 2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2011, 2015, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <[email protected]>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -54,18 +54,6 @@
 
 #ifndef CONFIG_DISABLE_SIGNALS
 
-/****************************************************************************
- * Pre-processor Definitions
- ****************************************************************************/
-
-/****************************************************************************
- * Private Data
- ****************************************************************************/
-
-/****************************************************************************
- * Private Functions
- ****************************************************************************/
-
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -113,9 +101,13 @@ void up_sigdeliver(void)
   sigdeliver           = rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
-  /* Then restore the task interrupt state */
+#ifndef CONFIG_SUPPRESS_INTERRUPTS
+  /* Then make sure that interrupts are enabled.  Signal handlers must always
+   * run with interrupts enabled.
+   */
 
-  up_irq_restore(regs[REG_EFLAGS]);
+  up_irq_enable();
+#endif
 
   /* Deliver the signals */