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Add bounds checking for output tensor buffer in wasi-nn llama.cpp #4847

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Add bounds checking for output tensor buffer in wasi-nn llama.cpp #4847

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acd36fc
Add bounds checking for output tensor buffer in wasi-nn llama.cpp
sumleo Feb 25, 2026
be99615
Return too_large error instead of silently truncating output
sumleo Feb 27, 2026
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22 changes: 18 additions & 4 deletions core/iwasm/libraries/wasi-nn/src/wasi_nn_llamacpp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -623,8 +623,15 @@ get_output(void *ctx, graph_execution_context exec_ctx, uint32_t index,
printf("%s\n", output_metadata);
}

memcpy(output_tensor->buf, output_metadata, strlen(output_metadata));
*output_tensor_size = strlen(output_metadata);
size_t metadata_len = strlen(output_metadata);
if (metadata_len > output_tensor->size) {
NN_ERR_PRINTF("Output buffer too small for metadata: "
"need %zu, got %zu",
metadata_len, output_tensor->size);
return too_large;
}
memcpy(output_tensor->buf, output_metadata, metadata_len);
*output_tensor_size = metadata_len;
return success;
}

Expand All @@ -643,8 +650,15 @@ get_output(void *ctx, graph_execution_context exec_ctx, uint32_t index,
printf("%s", buf);
}

memcpy(output_tensor->buf + end_pos, buf, strlen(buf));
end_pos += strlen(buf);
size_t piece_len = strlen(buf);
if (end_pos + piece_len > output_tensor->size) {
NN_ERR_PRINTF("Output buffer too small: need at least %zu,"
" got %zu",
end_pos + piece_len, output_tensor->size);
return too_large;
}
memcpy(output_tensor->buf + end_pos, buf, piece_len);
end_pos += piece_len;
}

if (backend_ctx->config.stream_stdout) {
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