[Runtime][4.2] In various enumTagSinglePayload functions, don't read getExtraInhabitantIndex or storeExtraInhabitant unless it actually has extra inhabitants. #17880
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…traInhabitantIndex or storeExtraInhabitant unless it actually has extra inhabitants. This code would previously read off the end of the allocated metadata to fetch these values. This was usually harmless, as the value was never used in that case. However, on rare occasions the metadata would be right before unmapped memory, and this read would crash trying to access that unmapped memory. rdar://problem/39866044
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@swift-ci please test |
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@swift-ci please nominate Explanation: A rare crash was caused by reading past the end of some metadata records. Most of the time it was harmless as the value was ignored, but if the read extended into unmapped memory, the program would crash. |
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Thank you! |
Cherry-pick #17879 to 4.2.
This code would previously read off the end of the allocated metadata to fetch these values. This was usually harmless, as the value was never used in that case. However, on rare occasions the metadata would be right before unmapped memory, and this read would crash trying to access that unmapped memory.
rdar://problem/39866044