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fix(moe): pad trtllm-gen route map by one element to avoid OOB read #4237

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Merged
samuellees merged 1 commit into from
Jul 29, 2026
Merged

fix(moe): pad trtllm-gen route map by one element to avoid OOB read #4237

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8 changes: 6 additions & 2 deletions csrc/trtllm_fused_moe_kernel_launcher.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -450,8 +450,10 @@ class FusedMoeLauncher {
expanded_idx_to_permuted_idx =
alloc_tensor({args->num_tokens * totalExpertsPerToken}, dl_int32, hidden_states.device());

// WAR: the routed batched-GEMM kernels read one int32 past the end of the route map.
// TODO: drop the +1 once the fixed kernel cubins land.
permuted_idx_to_token_idx =
alloc_tensor({max_num_padded_tokens}, dl_int32, hidden_states.device());
alloc_tensor({max_num_padded_tokens + 1}, dl_int32, hidden_states.device());

if (gemm1_bias_type == batchedGemm::gemm::BiasType::Mn) {
permuted_idx_to_expanded_idx =
Expand Down Expand Up @@ -1940,8 +1942,10 @@ class FP4BlockScaleLauncher : public FusedMoeLauncher {
total_num_padded_tokens = alloc_tensor({1}, dl_int32, hidden_states.device());
expanded_idx_to_permuted_idx =
alloc_tensor({args->num_tokens * args->top_k}, dl_int32, hidden_states.device());
// WAR: the routed batched-GEMM kernels read one int32 past the end of the route map.
// TODO: drop the +1 once the fixed kernel cubins land.
permuted_idx_to_token_idx =
alloc_tensor({max_num_padded_tokens}, dl_int32, hidden_states.device());
alloc_tensor({max_num_padded_tokens + 1}, dl_int32, hidden_states.device());

int64_t const size_of_expert_count_histogram = std::max(args->num_experts * 2, 256 * 2);
expert_count_histogram =
Expand Down
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