6.12-stable review patch. If anyone has any objections, please let me know.
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From: Tvrtko Ursulin tvrtko.ursulin@igalia.com
[ Upstream commit 6bd90e700b4285e6a7541e00f969cab0d696adde ]
Xe can free some of the data pointed to by the dma-fences it exports. Most notably the timeline name can get freed if userspace closes the associated submit queue. At the same time the fence could have been exported to a third party (for example a sync_fence fd) which will then cause an use- after-free on subsequent access.
To make this safe we need to make the driver compliant with the newly documented dma-fence rules. Driver has to ensure a RCU grace period between signalling a fence and freeing any data pointed to by said fence.
For the timeline name we simply make the queue be freed via kfree_rcu and for the shared lock associated with multiple queues we add a RCU grace period before freeing the per GT structure holding the lock.
Signed-off-by: Tvrtko Ursulin tvrtko.ursulin@igalia.com Reviewed-by: Matthew Brost matthew.brost@intel.com Acked-by: Lucas De Marchi lucas.demarchi@intel.com Signed-off-by: Tvrtko Ursulin tursulin@ursulin.net Link: https://lore.kernel.org/r/20250610164226.10817-5-tvrtko.ursulin@igalia.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/xe/xe_guc_exec_queue_types.h | 2 ++ drivers/gpu/drm/xe/xe_guc_submit.c | 7 ++++++- drivers/gpu/drm/xe/xe_hw_fence.c | 3 +++ 3 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/xe/xe_guc_exec_queue_types.h b/drivers/gpu/drm/xe/xe_guc_exec_queue_types.h index 4c39f01e4f52..a3f421e2adc0 100644 --- a/drivers/gpu/drm/xe/xe_guc_exec_queue_types.h +++ b/drivers/gpu/drm/xe/xe_guc_exec_queue_types.h @@ -20,6 +20,8 @@ struct xe_exec_queue; struct xe_guc_exec_queue { /** @q: Backpointer to parent xe_exec_queue */ struct xe_exec_queue *q; + /** @rcu: For safe freeing of exported dma fences */ + struct rcu_head rcu; /** @sched: GPU scheduler for this xe_exec_queue */ struct xe_gpu_scheduler sched; /** @entity: Scheduler entity for this xe_exec_queue */ diff --git a/drivers/gpu/drm/xe/xe_guc_submit.c b/drivers/gpu/drm/xe/xe_guc_submit.c index 0e17820a35e2..cf6946424fc3 100644 --- a/drivers/gpu/drm/xe/xe_guc_submit.c +++ b/drivers/gpu/drm/xe/xe_guc_submit.c @@ -1241,7 +1241,11 @@ static void __guc_exec_queue_fini_async(struct work_struct *w) xe_sched_entity_fini(&ge->entity); xe_sched_fini(&ge->sched);
- kfree(ge); + /* + * RCU free due sched being exported via DRM scheduler fences + * (timeline name). + */ + kfree_rcu(ge, rcu); xe_exec_queue_fini(q); xe_pm_runtime_put(guc_to_xe(guc)); } @@ -1427,6 +1431,7 @@ static int guc_exec_queue_init(struct xe_exec_queue *q)
q->guc = ge; ge->q = q; + init_rcu_head(&ge->rcu); init_waitqueue_head(&ge->suspend_wait);
for (i = 0; i < MAX_STATIC_MSG_TYPE; ++i) diff --git a/drivers/gpu/drm/xe/xe_hw_fence.c b/drivers/gpu/drm/xe/xe_hw_fence.c index 0b4f12be3692..6e2221b60688 100644 --- a/drivers/gpu/drm/xe/xe_hw_fence.c +++ b/drivers/gpu/drm/xe/xe_hw_fence.c @@ -100,6 +100,9 @@ void xe_hw_fence_irq_finish(struct xe_hw_fence_irq *irq) spin_unlock_irqrestore(&irq->lock, flags); dma_fence_end_signalling(tmp); } + + /* Safe release of the irq->lock used in dma_fence_init. */ + synchronize_rcu(); }
void xe_hw_fence_irq_run(struct xe_hw_fence_irq *irq)