[Lldb-commits] [PATCH] D136650: Add a check for TypeSystem use-after-free problems

Tue Oct 25 20:24:26 PDT 2022

aprantl added inline comments.

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Comment at: lldb/source/Symbol/CompilerType.cpp:35
+  bool unused;
+  if (GetTypeSystemGraveyard().Lookup(m_type_system, unused)) {
+    lldbassert(false && "CompilerType belongs to deleted Typesystem");
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hawkinsw wrote:
> I am sorry if this is obvious, but is `CompilerType` used in a multithreaded environment? So, is there a possibility that we could pass the check on line 32 but become invalid by the use of `m_type_system` here and fall victim to an attempt (in `Lookup`, perhaps?) to dereference a `NULL` pointer? Again, I am sorry if that is a stupid question!
Yes, CompilerType could be used on any thread and this will not catch a use-after-free if the TypeSystem is deleted between the IsValid check and its use.

A solution would be to store a TypeSystemSP/WP in CompilerType, but I'm expecting this to be rather expensive. The intention of this patch is as a bug-finding tool. It's not intended to make holding on to CompilerType objects safe. That said, I'm open to explore ideas for how to efficiently make this safe in a future patch.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D136650/new/

https://reviews.llvm.org/D136650