fix: add guards to oapi cufa opcode check #708
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ZNeumann
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Co-authored-by: Michal Nowacki <[email protected]>
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When instrumenting wordpress/drupal hooks, we want to instrument the hook function calls, which are dispatched by php's call_user_function_array. This php function (cufa for short) is flattened/inlined, so to determine if we are in a function called by a cufa call, we need to check the opcodes of the caller to the current function. If the caller is a php internal function, checking these opcodes was not safe and lead to invalid reads. As such, before reading the opcodes, we first check if the caller is a user function. We only want to instrument cufa calls from user functions anyway.