[PATCH v3 03/13] rv: Prevent in-flight per-task handlers from using invalid slots

[Gabriele Monaco]

Per-task monitors use a slot in the task_struct->rv[] array and store
that locally (e.g. task_mon_slot), this slot is returned during the
destruction process but currently hanlers can be running while that slot
is returning and this race may lead to accessing an invalid slot.

Synchronise with all in-flight tracepoint handlers using
tracepoint_synchronize_unregister() before returning the slot.

Fixes: f5587d1b6ec9 ("rv: Add Hybrid Automata monitor type")
Fixes: a9769a5b9878 ("rv: Add support for LTL monitors")
Suggested-by: Wen Yang <wen.yang@xxxxxxxxx>
Reviewed-by: Nam Cao <namcao@xxxxxxxxxxxxx>
Signed-off-by: Gabriele Monaco <gmonaco@xxxxxxxxxx>
---
 include/rv/da_monitor.h  | 4 ++++
 include/rv/ltl_monitor.h | 1 +
 2 files changed, 5 insertions(+)

diff --git a/include/rv/da_monitor.h b/include/rv/da_monitor.h
index 1459fb3df..cc97cc5df 100644
--- a/include/rv/da_monitor.h
+++ b/include/rv/da_monitor.h
@@ -302,6 +302,9 @@ static int da_monitor_init(void)
 
 /*
  * da_monitor_destroy - return the allocated slot
+ *
+ * Wait for all in-flight handlers before returning the slot to avoid
+ * out-of-bound accesses.
  */
 static inline void da_monitor_destroy(void)
 {
@@ -310,6 +313,7 @@ static inline void da_monitor_destroy(void)
 		return;
 	}
 
+	tracepoint_synchronize_unregister();
 	da_monitor_reset_all();
 
 	rv_put_task_monitor_slot(task_mon_slot);
diff --git a/include/rv/ltl_monitor.h b/include/rv/ltl_monitor.h
index eff60cd61..38e792401 100644
--- a/include/rv/ltl_monitor.h
+++ b/include/rv/ltl_monitor.h
@@ -77,6 +77,7 @@ static void ltl_monitor_destroy(void)
 {
 	rv_detach_trace_probe(name, task_newtask, handle_task_newtask);
 
+	tracepoint_synchronize_unregister();
 	rv_put_task_monitor_slot(ltl_monitor_slot);
 	ltl_monitor_slot = RV_PER_TASK_MONITOR_INIT;
 }
-- 
2.54.0