Check for debug offset compatibility before using the offsets

Author: godlygeek

Python/remote_debugging.c

@@ -668,6 +668,72 @@ write_memory(proc_handle_t *handle, uintptr_t remote_address, size_t len, const
 #endif
 }
 
+static int
+is_prerelease_version(uint64_t version)
+{
+    return (version & 0xF0) != 0xF0;
+}
+
+static int
+ensure_debug_offset_compatibility(const _Py_DebugOffsets* debug_offsets)
+{
+    if (memcmp(debug_offsets->cookie, _Py_Debug_Cookie, sizeof(debug_offsets->cookie)) != 0) {
+        // The remote is probably running a Python version predating debug offsets.
+        PyErr_SetString(
+            PyExc_RuntimeError,
+            "Can't determine the Python version of the remote process");
+        return -1;
+    }
+
+    // Assume debug offsets could change from one pre-release version to another,
+    // or one minor version to another, but are stable across patch versions.
+    if (is_prerelease_version(Py_Version) && Py_Version != debug_offsets->version) {
+        PyErr_SetString(
+            PyExc_RuntimeError,
+            "Can't send commands from a pre-release Python interpreter"
+            " to a process running a different Python version");
+        return -1;
+    }
+
+    if (is_prerelease_version(debug_offsets->version) && Py_Version != debug_offsets->version) {
+        PyErr_SetString(
+            PyExc_RuntimeError,
+            "Can't send commands to a pre-release Python interpreter"
+            " from a process running a different Python version");
+        return -1;
+    }
+
+    unsigned int remote_major = (debug_offsets->version >> 24) & 0xFF;
+    unsigned int remote_minor = (debug_offsets->version >> 16) & 0xFF;
+
+    if (PY_MAJOR_VERSION != remote_major || PY_MINOR_VERSION != remote_minor) {
+        PyErr_Format(
+            PyExc_RuntimeError,
+            "Can't send commands from a Python %d.%d process to a Python %d.%d process",
+            PY_MAJOR_VERSION, PY_MINOR_VERSION, remote_major, remote_minor);
+        return -1;
+    }
+
+    // The debug offsets differ between free threaded and non-free threaded builds.
+    if (_Py_Debug_Free_Threaded && !debug_offsets->free_threaded) {
+        PyErr_SetString(
+            PyExc_RuntimeError,
+            "Cannot send commands from a free-threaded Python process"
+            " to a process running a non-free-threaded version");
+        return -1;
+    }
+
+    if (!_Py_Debug_Free_Threaded && debug_offsets->free_threaded) {
+        PyErr_SetString(
+            PyExc_RuntimeError,
+            "Cannot send commands to a free-threaded Python process"
+            " from a process running a non-free-threaded version");
+        return -1;
+    }
+
+    return 0;
+}
+
 static int
 read_offsets(
     proc_handle_t *handle,
@@ -685,7 +751,10 @@ read_offsets(
     size_t size = sizeof(struct _Py_DebugOffsets);
     Py_ssize_t bytes = read_memory(
         handle, *runtime_start_address, size, debug_offsets);
-    if (bytes == -1) {
+    if (bytes < 0 || (size_t)bytes != size) {
+        return -1;
+    }
+    if (ensure_debug_offset_compatibility(debug_offsets)) {
         return -1;
     }
     return 0;