In affected versions, after a Report is constructed using wrap_err or wrap_err_with to attach a message of type D onto an error of type E, then using downcast to recover ownership of either the value of type D or the value of type E, one of two things can go wrong:
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If downcasting to E, there remains a value of type D to be dropped. It is incorrectly "dropped" by running E's drop behavior, rather than D's. For example if D is &str and E is std::io::Error, there would be a call of std::io::Error::drop in which the reference received by the Drop impl does not refer to a valid value of type std::io::Error, but instead to &str.
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If downcasting to D, there remains a value of type E to be dropped. When D and E do not happen to be the same size, E's drop behavior is incorrectly executed in the wrong location. The reference received by the Drop impl may point left or right of the real E value that is meant to be getting dropped.
In both cases, when the Report contains an error E that has nontrivial drop behavior, the most likely outcome is memory corruption.
When the Report contains an error E that has trivial drop behavior (for example a Utf8Error) but where D has nontrivial drop behavior (such as String), the most likely outcome is that downcasting to E would leak D.
References
In affected versions, after a
Reportis constructed usingwrap_errorwrap_err_withto attach a message of typeDonto an error of typeE, then usingdowncastto recover ownership of either the value of typeDor the value of typeE, one of two things can go wrong:If downcasting to
E, there remains a value of typeDto be dropped. It is incorrectly "dropped" by runningE's drop behavior, rather thanD's. For example ifDis&strandEisstd::io::Error, there would be a call ofstd::io::Error::dropin which the reference received by theDropimpl does not refer to a valid value of typestd::io::Error, but instead to&str.If downcasting to
D, there remains a value of typeEto be dropped. WhenDandEdo not happen to be the same size,E's drop behavior is incorrectly executed in the wrong location. The reference received by theDropimpl may point left or right of the realEvalue that is meant to be getting dropped.In both cases, when the
Reportcontains an errorEthat has nontrivial drop behavior, the most likely outcome is memory corruption.When the
Reportcontains an errorEthat has trivial drop behavior (for example aUtf8Error) but whereDhas nontrivial drop behavior (such asString), the most likely outcome is that downcasting toEwould leakD.References