gh-144319: Fix huge page leak in datastack chunk allocator#147963
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pablogsal merged 1 commit intopython:mainfrom Apr 5, 2026
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gh-144319: Fix huge page leak in datastack chunk allocator#147963pablogsal merged 1 commit intopython:mainfrom
pablogsal merged 1 commit intopython:mainfrom
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Other than the stylistic stuff @maurycy pointed out, I think this looks fine.
The original fix rounded datastack chunk allocations in pystate.c so that _PyObject_VirtualFree() would receive the full huge page mapping size. Change direction and move that logic into _PyObject_VirtualAlloc() and _PyObject_VirtualFree() instead. The key invariant is that munmap() must see the full mapped size, so alloc and free now apply the same platform-specific rounding in the allocator layer. This keeps _PyStackChunk bookkeeping in requested-size units, avoids a hardcoded 2 MB assumption, and also covers other small virtual-memory users such as the JIT tracer state allocation in optimizer.c.
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The datastack chunk allocator (
allocate_chunkinpystate.c) and othersmall virtual-memory users such as the JIT tracer allocate through
_PyObject_VirtualAlloc()using the logical requested size. When huge pagesare enabled, the arena allocator may round those mappings up to the platform
huge page size, so freeing with the smaller requested size can make
munmap()fail withEINVALand leak the mapping.This change moves the rounding logic into
_PyObject_VirtualAlloc()/_PyObject_VirtualFree()so allocation and free always agree on the fullmapped size. Keeping it in the allocator layer also avoids a hardcoded 2 MB
assumption in
pystate.cand fixes the JIT tracer allocation path at thesame time.