[release/10.0] Fix g_gc_lowest_address updating - #131432
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Backport of dotnet#131324 to release/10.0
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Pull request overview
This PR backports a CoreCLR GC fix to release/10.0 to prevent g_gc_lowest_address from being incorrectly updated to 0 in a rare address-space edge case, which could cause GC to treat NULL references as heap references and crash.
Changes:
- Fixes an edge-condition comparison (
>→>=) when expanding the GC address range downward so the lowest address is clamped toOS_PAGE_SIZEinstead of becoming 0.
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@janvorli, it's approved. Please get code review and check test results after CI done. |
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@kkokosa, please do code review. I need a sign-off to merge a servicing PR. |
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Backport of #131324 to release/10.0
Customer Impact
There is a rare issue that occurs when virtual memory blocks allocated by GC end up getting addresses that trigger a code path where the GC address space range maintained by GC in
g_gc_lowest_address..g_gc_highest_addressis expanded down and theg_gc_lowest_addressis exactly 2/3 of theg_gc_highest_address. We end up setting theg_gc_lowest_addressto 0This leads to crashes during GC because it starts considering NULL references as valid references being part of the GC heap.
Regression
Testing
Regular coreclr / libraries tests.
Risk
Low. The change just makes single condition correct for the edge case causing the issue.