nouveau: fix client work fence deletion race

This seems to have existed for ever but is now more apparant after commit 9bff18d13473 ("drm/ttm: use per BO cleanup workers") My analysis: two threads are running, one in the irq signalling the fence, in dma_fence_signal_timestamp_locked, it has done the DMA_FENCE_FLAG_SIGNALLED_BIT setting, but hasn't yet reached the callbacks. The second thread in nouveau_cli_work_ready, where it sees the fence is signalled, so then puts the fence, cleanups the object and frees the work item, which contains the callback. Thread one goes again and tries to call the callback and causes the use-after-free. Proposed fix: lock the fence signalled check in nouveau_cli_work_ready, so either the callbacks are done or the memory is freed.

Dave Airlie committed 3 years ago

Commit c8a5d5e1 parent c8ac1091 file · +10 −4Browse files

Unified · Split

drivers/gpu/drm/nouveau/nouveau_drm.c+10−4

@@ -137,10 +137,16 @@ nouveau_name(struct drm_device *dev) · 136 unmodified lines
137	137	static inline bool
138	138	nouveau_cli_work_ready(struct dma_fence *fence)
139	139	{
140		− if (!dma_fence_is_signaled(fence))
141		− return false;
142		− dma_fence_put(fence);
143		− return true;
	140	+ bool ret = true;
	141	+
	142	+ spin_lock_irq(fence->lock);
	143	+ if (!dma_fence_is_signaled_locked(fence))
	144	+ ret = false;
	145	+ spin_unlock_irq(fence->lock);
	146	+
	147	+ if (ret == true)
	148	+ dma_fence_put(fence);
	149	+ return ret;
144	150	}
145	151
146	152	static void