During release of the syncpt, we remove it from the list of syncpt and the tree, but only if it is not already been removed. However, during signaling, we first remove the syncpt from the list. So, if we concurrently free and signal the syncpt, the free may decide that it is not part of the tree and immediately free itself -- meanwhile the signaler goes on to use the now freed datastructure. In particular, we get struck by commit 0e2f733addbf ("dma-buf: make dma_fence structure a bit smaller v2") as the cb_list is immediately clobbered by the kfree_rcu. v2: Avoid calling into timeline_fence_release() from under the spinlock
Unified · Split
| @@ -132,17 +132,14 @@ static void timeline_fence_release(struct dma_fence *fence) · 131 unmodified lines | ||
| 132 | 132 | { |
| 133 | 133 | struct sync_pt *pt = dma_fence_to_sync_pt(fence); |
| 134 | 134 | struct sync_timeline *parent = dma_fence_parent(fence); |
| 135 | + unsigned long flags; | |
| 135 | 136 | |
| 137 | + spin_lock_irqsave(fence->lock, flags); | |
| 136 | 138 | if (!list_empty(&pt->link)) { |
| 137 | − unsigned long flags; | |
| 138 | − | |
| 139 | − spin_lock_irqsave(fence->lock, flags); | |
| 140 | − if (!list_empty(&pt->link)) { | |
| 141 | − list_del(&pt->link); | |
| 142 | − rb_erase(&pt->node, &parent->pt_tree); | |
| 143 | − } | |
| 144 | − spin_unlock_irqrestore(fence->lock, flags); | |
| 139 | + list_del(&pt->link); | |
| 140 | + rb_erase(&pt->node, &parent->pt_tree); | |
| 145 | 141 | } |
| 142 | + spin_unlock_irqrestore(fence->lock, flags); | |
| 146 | 143 | |
| 147 | 144 | sync_timeline_put(parent); |
| 148 | 145 | dma_fence_free(fence); |
| @@ -265,7 +262,8 @@ static struct sync_pt *sync_pt_create(struct sync_timeline *obj, · 116 unmodified lines | ||
| 265 | 262 | p = &parent->rb_left; |
| 266 | 263 | } else { |
| 267 | 264 | if (dma_fence_get_rcu(&other->base)) { |
| 268 | − dma_fence_put(&pt->base); | |
| 265 | + sync_timeline_put(obj); | |
| 266 | + kfree(pt); | |
| 269 | 267 | pt = other; |
| 270 | 268 | goto unlock; |
| 271 | 269 | } |