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[ET-VK] Fix use-after-free in PrepackNode when TensorRefs are shared #18906

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Merged
meta-codesync merged 2 commits into from
Apr 15, 2026
+13 −7
Merged

[ET-VK] Fix use-after-free in PrepackNode when TensorRefs are shared #18906

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586cce1
[ET-VK] Fix use-after-free in PrepackNode when TensorRefs are shared
Apr 15, 2026
5fd2bae
Update on "[ET-VK] Fix use-after-free in PrepackNode when TensorRefs …
Apr 15, 2026
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2 changes: 0 additions & 2 deletions backends/vulkan/runtime/graph/ComputeGraph.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1135,8 +1135,6 @@ void ComputeGraph::prepack() {
int i = 0;
bool submitted = false;
const bool reduce_peak_memory = total_constant_nbytes_ > 10 * MB;
// int count = 0;

context_->set_cmd();
for (std::unique_ptr<PrepackNode>& node : prepack_nodes_) {
// Do not trigger on the first or last prepack node.
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8 changes: 6 additions & 2 deletions backends/vulkan/runtime/graph/containers/Constant.h
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Expand Up @@ -29,6 +29,12 @@ struct TensorRef final {
// This will be empty (default constructed) for the raw pointer constructor
executorch::runtime::FreeableBuffer buffer;

// Number of PrepackNodes that still need to read from this TensorRef. When
// this reaches 0, the buffer can be safely freed. This prevents
// use-after-free when multiple PrepackNodes reference the same TensorRef
// (e.g. shared/tied weights).
int32_t prepack_use_count{0};

explicit TensorRef(
const std::vector<int64_t>& t_sizes,
vkapi::ScalarType t_dtype,
Expand All @@ -44,8 +50,6 @@ struct TensorRef final {
return utils::multiply_integers(sizes) * vkapi::element_size(dtype);
}

// Manually free the buffer if needed (though it will be freed automatically
// on destruction)
void free_buffer() {
buffer.Free();
}
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10 changes: 7 additions & 3 deletions backends/vulkan/runtime/graph/ops/PrepackNode.cpp
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Expand Up @@ -44,6 +44,9 @@ PrepackNode::PrepackNode(
push_constants_(push_constants) {
graph.update_descriptor_counts(shader, /*execute = */ false);
graph.update_descriptor_counts(noop_shader_, /*execute = */ false);
if (!graph.val_is_none(tref)) {
graph.get_tref(tref)->prepack_use_count++;
}
}

api::StagingBuffer PrepackNode::create_staging_buffer(ComputeGraph* graph) {
Expand Down Expand Up @@ -100,9 +103,10 @@ api::StagingBuffer PrepackNode::create_staging_buffer(ComputeGraph* graph) {
}
}

// Once the staging buffer is copied, if the TensorRef owns a FreeableBuffer,
// it can be freed.
tref->free_buffer();
if (--tref->prepack_use_count == 0) {
tref->free_buffer();
}

return staging;
}

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