How to reproduce:
1. Open the user attached project (LinuxUndoCrash.zip)
2. Select the top-most GameObject called 'UModeler Object' from the Hierarchy
3. Select the "Polygon Tool" in the toolbar at the top of the Scene View (cube with a highlighted side)
4. In the Inspector window find the "All Selection Tool" (you can use the search or switch to text-based mode by right-clicking inside the tool area)
5. Start selecting this tool to rapidly select/unselect all polygons
6. If the crash does not occur within about 10 seconds, try selecting another object and repeating the process

Reproducible with: 2021.2.5f1, 2022.1.0a3
Not reproducible with: 2020.3.24f1, 2022.1.0a4, 2022.1.0b1
Could not test with: 2019.4.32f1 (due to compilation errors the UModeler no longer works)

Reproducible on Ubuntu 20.04
Not reproducible on Windows 10

Crash stacktrace:
#0 0x007fb8647993c0 in funlockfile
#1 0x005627b3e562f4 in CompareObjectUndo(UndoBase*, Object*, Object**, int)
#2 0x005627b3e5426d in StructureUndoManager::RecordStructureChange(Object&, UndoManager::UndoScope, StructureUndoBase::ChangeType, core::basic_string<char, core::StringStorageDefault<char> > const&, int, Object**, int)
#3 0x005627b3e54919 in RegisterUndo(Object*, Object**, int, core::basic_string<char, core::StringStorageDefault<char> > const&, int)
#4 0x005627b38b618d in UndoBindings::RegisterCompleteObjectUndoMultiple(Object*, ScriptingArrayPtr, core::basic_string<char, core::StringStorageDefault<char> > const&, int, ScriptingExceptionPtr*)
#5 0x005627b263b7ed in Undo_CUSTOM_RegisterCompleteObjectUndoMultiple(ScriptingBackendNativeObjectPtrOpaque*, ScriptingBackendNativeArrayPtrOpaque*, ScriptingBackendNativeStringPtrOpaque*, int)
#6 0x0000004111c6ff in (wrapper managed-to-native) UnityEditor.Undo:RegisterCompleteObjectUndoMultiple (UnityEngine.Object,UnityEngine.Object[],string,int)