Debugger: Prevent Abort on Invalid Virtual Method #2115
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If the debugger is asked to invoke an interface or virtual method on a class the mono_object_get_virtual_method_internal will assert & abort (or crash). mono_object_get_virtual_method_internal assumes that it is being asked to invoke a virtual method on an instance that implements it. If that's not true it will assert & abort or access invalid memory if assertions are disabled. To protect against this we check if the this_arg can be cast to the interface or base class type. If it can then we should be safe to call mono_object_get_virtual_method_internal.
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Were you able to reproduce this issue with the upstream mono in dotnet/runtime? It doesn't look like this change is there so it might be worthwhile upstreaming the change unless they've fixed it in some other way. |
joncham
reviewed
Mar 3, 2025
| @@ -6545,6 +6545,10 @@ do_invoke_method (DebuggerTlsData *tls, Buffer *buf, InvokeData *invoke, guint8 | |||
| PRINT_DEBUG_MSG (1, "[%p] Error: Interface method invoked without this argument.\n", (gpointer) (gsize) mono_native_thread_id_get ()); | |||
| return ERR_INVALID_ARGUMENT; | |||
| } | |||
| if (!mono_object_isinst(this_arg, m->klass)) { | |||
| PRINT_DEBUG_MSG (1, "[%p] Error: Interface method invoked on object that doesn't implement the interface.\n", (gpointer) (gsize) mono_native_thread_id_get ()); | |||
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Nit, should the message include more info like type and interface/and method name?
joncham
approved these changes
Mar 3, 2025
UnityAlex
approved these changes
Mar 4, 2025
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If the debugger is asked to invoke an interface or virtual method on a class the mono_object_get_virtual_method_internal will assert & abort (or crash).
mono_object_get_virtual_method_internal assumes that it is being asked to invoke a virtual method on an instance that implements it. If that's not true it will assert & abort or access invalid memory if assertions are disabled.
To protect against this we check if the this_arg can be cast to the interface or base class type. If it can then we should be safe to call mono_object_get_virtual_method_internal.
Reviewers: please consider these questions as well! ❤️
Release notes
Fixed UUM-97917 @scott-ferguson-unity
Mono: Prevent debugger crash when watching or evaluating an interface property or method without an instance (i.e. nameof(IInterface.Property).