Make sure to call PyErr before calling set_exception_cause

Author: taegyunkim

Modules/_remote_debugging/asyncio.c

@@ -117,6 +117,7 @@ iterate_set_entries(
 
     // Validate mask and num_els to prevent huge loop iterations from garbage data
     if (mask < 0 || mask >= MAX_SET_TABLE_SIZE || num_els < 0 || num_els > mask + 1) {
+        PyErr_SetString(PyExc_RuntimeError, "Invalid set object (corrupted remote memory)");
         set_exception_cause(unwinder, PyExc_RuntimeError,
             "Invalid set object (corrupted remote memory)");
         return -1;

Modules/_remote_debugging/code_objects.c

@@ -446,6 +446,9 @@ parse_code_object(RemoteUnwinderObject *unwinder,
     if (tlbc_entry) {
         // Validate index bounds (also catches negative values since tlbc_index is signed)
         if (ctx->tlbc_index < 0 || ctx->tlbc_index >= tlbc_entry->tlbc_array_size) {
+            PyErr_Format(PyExc_RuntimeError,
+                "Invalid tlbc_index %d (array size %zd, corrupted remote memory)",
+                ctx->tlbc_index, tlbc_entry->tlbc_array_size);
             set_exception_cause(unwinder, PyExc_RuntimeError,
                 "Invalid tlbc_index (corrupted remote memory)");
             goto error;

Modules/_remote_debugging/frames.c

@@ -49,6 +49,8 @@ process_single_stack_chunk(
         // Size must be at least enough for the header and reasonably bounded
         if (actual_size <= offsetof(_PyStackChunk, data) || actual_size > MAX_STACK_CHUNK_SIZE) {
             PyMem_RawFree(this_chunk);
+            PyErr_Format(PyExc_RuntimeError,
+                "Invalid stack chunk size %zu (corrupted remote memory)", actual_size);
             set_exception_cause(unwinder, PyExc_RuntimeError,
                 "Invalid stack chunk size (corrupted remote memory)");
             return -1;
@@ -244,6 +246,7 @@ parse_frame_from_chunks(
 ) {
     void *frame_ptr = find_frame_in_chunks(chunks, address);
     if (!frame_ptr) {
+        PyErr_Format(PyExc_RuntimeError, "Frame at address 0x%lx not found in stack chunks", address);
         set_exception_cause(unwinder, PyExc_RuntimeError, "Frame not found in stack chunks");
         return -1;
     }

Modules/_remote_debugging/module.c

@@ -595,6 +595,9 @@ _remote_debugging_RemoteUnwinder_get_stack_trace_impl(RemoteUnwinderObject *self
                     // Detect cycle: if current_tstate didn't advance, we have corrupted data
                     if (current_tstate == prev_tstate) {
                         Py_DECREF(interpreter_threads);
+                        PyErr_Format(PyExc_RuntimeError,
+                            "Thread list cycle detected at address 0x%lx (corrupted remote memory)",
+                            current_tstate);
                         set_exception_cause(self, PyExc_RuntimeError,
                             "Thread list cycle detected (corrupted remote memory)");
                         Py_CLEAR(result);