Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
Pre-existing issues: - [High] Use-After-Free (Incomplete Fix) -- commit a4cb3c10462917197ec6f8cdfe7a265ad10ef18a Author: Jonghyuk Kim(MalHyuk) <[email protected]> drm/nouveau: RCU-free the scheduler-containing nouveau_sched This commit attempts to fix a use-after-free issue by deferring the freeing of the scheduler object to an RCU callback. > diff --git a/drivers/gpu/drm/nouveau/nouveau_sched.c > b/drivers/gpu/drm/nouveau/nouveau_sched.c > index 8b9f935afe094..b3f02c490ecb6 100644 > --- a/drivers/gpu/drm/nouveau/nouveau_sched.c > +++ b/drivers/gpu/drm/nouveau/nouveau_sched.c > @@ -517,7 +517,7 @@ nouveau_sched_destroy(struct nouveau_sched **psched) > struct nouveau_sched *sched = *psched; > > nouveau_sched_fini(sched); > - kfree(sched); > + kfree_rcu(sched, rcu); [Severity: High] This isn't a bug introduced by this patch, but does this actually fix the underlying use-after-free issue? Using kfree_rcu() only defers freeing the scheduler by a single RCU grace period. However, dma_fence objects exported to userspace (e.g., via sync_file) can outlive this grace period since userspace controls the file descriptor lifetime. When userspace eventually queries the fence info, sync_fill_fence_info() acquires a new rcu_read_lock() and calls dma_fence_timeline_name(), which invokes drm_sched_fence_get_timeline_name(): drivers/gpu/drm/scheduler/sched_fence.c:drm_sched_fence_get_timeline_name() { ... return (const char *)fence->sched->name; } Because the nouveau_sched memory is physically freed after the initial RCU grace period elapses, this new RCU read-side critical section does not protect it. Won't this unconditionally dereference fence->sched->name on the already-freed memory, resulting in the exact same use-after-free read this patch intends to fix? > > *psched = NULL; > } -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=1
