On Tue, Apr 22, 2025 at 11:39:11AM +0100, Tvrtko Ursulin wrote: > Question I raised is if there are other drivers which manage to clean up > everything correctly (like the mock scheduler does), but trigger that > warning. Maybe there are not and maybe mock scheduler is the only false > positive.
So far the scheduler simply does not give any guideline on how to address the problem, hence every driver simply does something (or nothing, effectively ignoring the problem). This is what we want to fix. The mock scheduler keeps it's own list of pending jobs and on tear down stops the scheduler's workqueues, traverses it's own list and eventually frees the pending jobs without updating the scheduler's internal pending list. So yes, it does avoid memory leaks, but it also leaves the schedulers internal structures with an invalid state, i.e. the pending list of the scheduler has pointers to already freed memory. What if the drm_sched_fini() starts touching the pending list? Then you'd end up with UAF bugs with this implementation. We cannot invalidate the schedulers internal structures and yet call scheduler functions - e.g. drm_sched_fini() - subsequently. Hence, the current implementation of the mock scheduler is fundamentally flawed. And so would be *every* driver that still has entries within the scheduler's pending list. This is not a false positive, it already caught a real bug -- in the mock scheduler. - Danilo
