[release/6.0] [mono] Fix downcast check in Array.CopySlow #64479
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where each element in the source array is the appropriate type
When we have to resort to checking element by element, compare the type of each actual element with the destination type. In particular, not the destinations underlying type when it's an enum - we don't want to allow unrelated enums using the same representation to copy over. Fixes #64387
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I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label. |
lambdageek
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Feb 1, 2022
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coreclr failure is unrelated |
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Failure is: #64389 |
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Backport of #64469 to release/6.0
/cc @lambdageek
Customer Impact
Valid customer code that copies
object[]to a more specific array type with Enum elements may throw unexpected InvalidCastExceptions on WebAssembly, iOS and Android despite working in desktop configurations.Testing
Manual testing and CI regression testing.
Risk
Moderate: The fix removes a one type check and relaxes another before performing an unsafe copy operation. Existing code is unlikely to become broken. New code may incorrectly allow an unexpected copy of some valuetypes leading to silent data corruption instead of a runtime exception.