So far we had the approach of using a directed acyclic graph with the dma_resv obj.
This turned out to have many downsides, especially it means that every single driver and user of this interface needs to be aware of this restriction when adding fences. If the rules for the DAG are not followed then we end up with potential hard to debug memory corruption, information leaks or even elephant big security holes because we allow userspace to access freed up memory.
Since we already took a step back from that by always looking at all fences we now go a step further and stop dropping the shared fences when a new exclusive one is added.
Signed-off-by: Christian König christian.koenig@amd.com --- drivers/dma-buf/dma-resv.c | 14 +------------- 1 file changed, 1 insertion(+), 13 deletions(-)
diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c index 539b9b1df640..3b0001c5ff3a 100644 --- a/drivers/dma-buf/dma-resv.c +++ b/drivers/dma-buf/dma-resv.c @@ -411,29 +411,17 @@ EXPORT_SYMBOL(dma_resv_replace_fences); void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence) { struct dma_fence *old_fence = dma_resv_excl_fence(obj); - struct dma_resv_list *old; - u32 i = 0;
dma_resv_assert_held(obj);
- old = dma_resv_shared_list(obj); - if (old) - i = old->shared_count; - dma_fence_get(fence);
write_seqcount_begin(&obj->seq); /* write_seqcount_begin provides the necessary memory barrier */ RCU_INIT_POINTER(obj->fence_excl, fence); - if (old) - old->shared_count = 0; + dma_resv_list_prune(dma_resv_shared_list(obj), obj); write_seqcount_end(&obj->seq);
- /* inplace update, no shared fences */ - while (i--) - dma_fence_put(rcu_dereference_protected(old->shared[i], - dma_resv_held(obj))); - dma_fence_put(old_fence); } EXPORT_SYMBOL(dma_resv_add_excl_fence);