RUSTSEC-2021-0083

QueryInterface should call AddRef before returning pointer

Issued
Package
derive-com-impl (crates.io)
Type
Vulnerability
Categories
  • memory-corruption
Details
https://github.com/Connicpu/com-impl/issues/1
Patched
  • >=0.1.2
Keywords
  • com
  • queryinterface
  • addref
Affected Functions
Version
derive_com_impl::derive_com_impl
  • <=0.1.1

Description

Affected version of this crate, which is a required dependency in com-impl, provides a faulty implementation of the IUnknown::QueryInterface method.

QueryInterface implementation must call IUnknown::AddRef before returning the pointer, as describe in this documentation: https://docs.microsoft.com/en-us/windows/win32/api/unknwn/nf-unknwn-iunknown-queryinterface(refiid_void)

As it is not incrementing the refcount as expected, the following calls to IUnknown::Release method will cause WMI to drop reference to the interface, and can lead to invalid reference.

This is documented in https://docs.microsoft.com/en-us/windows/win32/learnwin32/managing-the-lifetime-of-an-object#reference-counting

There is no simple workaround, as you can't know how many time QueryInterface will be called. The only way to quick fix this is to use the macro expanded version of the code and modify the QueryInterface method to add the AddRef call yourself.

The issue was corrected in commit 9803f31fbd1717d482d848f041044d061fca6da7.

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