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ll-scheduler: only modify the task if it is valid 

schedule_ll_task_cancel() looks for a task on the list to cancel it.
However, if it doesn't find the task on the list it still sets its
status and deletes it from the list. Currently this doesn't cause
any problems, but it's potentially dangerous. This function can be
called for completed tasks, which are no longer on the list. So
list_item_del() will be called for the second time for it. Currently
this isn't a problem because SOF implementation of that function
also initialises the list head, but not all doubly-linked list
implementations do that. E.g. Zephyr's sys_dlist_remove() nullifies
both .next and .prev, so, a repeated call to it would cause a
NULL dereference. In general it's safer to only modify an element
when it has been verified to be valid.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
This commit is contained in:
Guennadi Liakhovetski 2021-05-19 10:46:12 +02:00 committed by Liam Girdwood
parent 2617ccb68a
commit 90045619d3
1 changed files with 5 additions and 4 deletions
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9
src/schedule/ll_schedule.c
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@ -537,14 +537,15 @@ static int schedule_ll_task_cancel(void *data, struct task *task)
/* found it */
if (curr_task == task) {
schedule_ll_domain_clear(sch, task);
/* remove work from list */
task->state = SOF_TASK_STATE_CANCEL;
list_item_del(&task->list);
break;
}
}
/* remove work from list */
task->state = SOF_TASK_STATE_CANCEL;
list_item_del(&task->list);
irq_local_enable(flags);
return 0;