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[Mono] Fix OP_CHECK_THIS to read 1 byte instead of 4/8 on x86/x64/LLVM. - #74638
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lateralusX
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SamMonoRT, lambdageek and vargaz
as code ownersAugust 26, 2022 09:57
lambdageek
approved these changes
Aug 26, 2022
lambdageek
commented
Aug 26, 2022
Member
We should backport this |
lateralusX
commented
Aug 29, 2022
MemberAuthor
/azp run runtime-extra-platforms |
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Azure Pipelines successfully started running 1 pipeline(s). |
MemberAuthor
Failures in runtime-extra-platforms seems unrelated and appears on multiple other PR's. |
lateralusX
commented
Aug 29, 2022
MemberAuthor
/backport to release/7.0 |
Contributor
Started backporting to release/7.0: https://github.com/dotnet/runtime/actions/runs/2950110740 |
Current implementation of OP_CHECK_THIS on x86/x64 and LLVM does a memory read of at least 4 bytes. This creates an issue when the target is a managed pointer, since that could point to the interior of a type, meaning it can read pass the allocated memory causing a crash. Fix change the size of the read to one byte since the only reason doing the read is to validate that the reference, managed pointer is not NULL. Reading only one byte is also inline with how it is implemented on arm/arm64, and it will reduce potential unaligned reads on x86/x64. Full fix for, dotnet#74179.
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31fabbdComparelateralusX
commented
Aug 30, 2022
MemberAuthor
Rebased to get CI run after #74567 had been merged and tests had been re-enabled. |
lateralusX
commented
Aug 30, 2022
MemberAuthor
/azp run runtime-extra-platforms |
|
Azure Pipelines successfully started running 1 pipeline(s). |
MemberAuthor
Failures looks unrelated and had failed in similar ways on other PR's as well. |
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Current implementation of OP_CHECK_THIS on x86/x64 and LLVM does a memory read of at least 4 bytes. This creates an issue when the target is a managed pointer, since that could point to the interior of a type, meaning it can read pass the allocated memory causing a crash. Fix change the size of the read to one byte since the only reason doing the read is to validate that the reference, managed pointer is not NULL. Reading only one byte is also inline with how it is implemented on arm/arm64, and it will reduce potential unaligned reads on x86/x64.
Full fix for, #74179.
Fixes#74179