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base repository: dotnet/runtime
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  • 4 commits
  • 17 files changed
  • 4 contributors

Commits on Apr 13, 2021

  1. Remove unused ParamTypes method from DispatchProxyGenerator (#51119)

    @campersau
    campersau authored Apr 13, 2021
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  2. Fix card mark stealing issue (#51104) 

    Fix issue with card marking stealing where getting a new chunk caused the "card" variable to go backwards. This caused an extra call to card_transition, which in turn caused cards to be cleared that should be set. The ultimate result is memory corruption.

Here are the conditions that cause the bug to surface:
- an object containing pointers that straddles a 2 MB boundary
- the objects contains just value types (i.e. no pointers) for at least 256 bytes after the 2 MB boundary
- there is a generation-crossing pointer afterwards in the same object
- but that is the only generation-crossing pointer in that 256 byte range

The bug comes about because of the following sequence of events:
- in mark_through_cards_for_segments, we scan an object at the end of a 2 MB chunk
- we encounter a pointer location that is already outside of that chunk (it belongs to card 2 in the next chunk)
- we call card_transition, which advances the card to the card of the pointer location (i.e., to card 2 in the next chunk)
- we realize that we need to get a new chunk
- when we get the chunk, we set the card to card 0 in the chunk
- we return to mark_through_cards_for_segments
- as the next chunk is adjacent to the current one, we continue processing the current object
- when we encounter the next pointer location in the object, we trigger a card_transition again
- this will erroneously not clear cards 0 and 1 because we think it there is a cross-gen pointer
- it will also reset the cross-gen generation pointer counter
- thus, if there are no other cross-generation pointers in the 256 bytes described by card 2, card 2 will be erroneously cleared
- having cards cleared erroneously ultimately leads to heap corruption

The fix simply makes sure the "card" variable doesn't go backwards in find_next_chunk.

It fixes the issue because it avoids the double card_transition.

It is safe because during iteration of a segment, the "card" variable must always increase. When we switch to another segment, it may decrease, but that is fine because in this case it will be re-initialized by the logic in mark_through_cards_segments.
    @PeterSolMS
    PeterSolMS authored Apr 13, 2021
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  3. Separate GetResourceString method with defaultString value. (#51073) 

    It's not used in Release build and it injects ununsed null value to every callsite
    @marek-safar
    marek-safar authored Apr 13, 2021
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  4. Return iOS version in Environment.OSVersion on Mac Catalyst (#50990) 

    * Return iOS version in Environment.OSVersion on Mac Catalyst.
Implement OperatingSystem.IsMacCatalyst and OperatingSystem.IsMacCatalystVersionAtLeast.

* Address feedback

* Ensure NSThread is in multi-threaded mode before using autorelease pool
    @filipnavara
    filipnavara authored Apr 13, 2021
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