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[3.14] gh-140067: Fix memory leak in sub-interpreter creation (GH-140111) (#140118)

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* [3.14] gh-140067: Fix memory leak in sub-interpreter creation  (GH-140111)

Fix memory leak in sub-interpreter creation caused by overwriting of the previously used `_malloced` field. Now the pointer is stored in the first word of the memory block to avoid it being overwritten accidentally.
(cherry picked from commit 59547a251f)

Co-authored-by: Shamil <ashm.tech@proton.me>
Co-authored-by: Kumar Aditya <kumaraditya@python.org>
This commit is contained in:
Kumar Aditya 2025-10-18 19:40:43 +05:30 • committed by GitHub
parent 3ca7ea1f8f
commit 1d11627ba5
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GPG key ID: B5690EEEBB952194
4 changed files with 12 additions and 10 deletions
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15
Python/pystate.c
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@ -565,16 +565,19 @@ _PyInterpreterState_Enable(_PyRuntimeState *runtime)
static PyInterpreterState *
alloc_interpreter(void)
{
// Aligned allocation for PyInterpreterState.
// the first word of the memory block is used to store
// the original pointer to be used later to free the memory.
size_t alignment = _Alignof(PyInterpreterState);
size_t allocsize = sizeof(PyInterpreterState) + alignment - 1;
size_t allocsize = sizeof(PyInterpreterState) + sizeof(void *) + alignment - 1;
void *mem = PyMem_RawCalloc(1, allocsize);
if (mem == NULL) {
return NULL;
}
PyInterpreterState *interp = _Py_ALIGN_UP(mem, alignment);
assert(_Py_IS_ALIGNED(interp, alignment));
interp->_malloced = mem;
return interp;
void *ptr = _Py_ALIGN_UP((char *)mem + sizeof(void *), alignment);
((void **)ptr)[-1] = mem;
assert(_Py_IS_ALIGNED(ptr, alignment));
return ptr;
}
static void
@ -589,7 +592,7 @@ free_interpreter(PyInterpreterState *interp)
interp->obmalloc = NULL;
}
assert(_Py_IS_ALIGNED(interp, _Alignof(PyInterpreterState)));
PyMem_RawFree(interp->_malloced);
PyMem_RawFree(((void **)interp)[-1]);
}
}