https://github.com/python/cpython/commit/427e7fc099e61d9a3d1f04e2fbde8b749e5fcf0a
commit: 427e7fc099e61d9a3d1f04e2fbde8b749e5fcf0a
branch: main
author: Bénédikt Tran <[email protected]>
committer: picnixz <[email protected]>
date: 2025-04-19T11:03:06+02:00
summary:
gh-132399: ensure correct alignment of `PyInterpreterState` (#132428)
files:
M Include/internal/pycore_interp_structs.h
M Python/pystate.c
diff --git a/Include/internal/pycore_interp_structs.h
b/Include/internal/pycore_interp_structs.h
index 573b56a57e1d54..9ac4b4630abd3f 100644
--- a/Include/internal/pycore_interp_structs.h
+++ b/Include/internal/pycore_interp_structs.h
@@ -754,6 +754,12 @@ struct _is {
* and should be placed at the beginning. */
struct _ceval_state ceval;
+ /* This structure is carefully allocated so that it's correctly aligned
+ * to avoid undefined behaviors during LOAD and STORE. The '_malloced'
+ * field stores the allocated pointer address that will later be freed.
+ */
+ void *_malloced;
+
PyInterpreterState *next;
int64_t id;
diff --git a/Python/pystate.c b/Python/pystate.c
index ee35f0fa945f8b..aba558279a657d 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -569,11 +569,19 @@ _PyInterpreterState_Enable(_PyRuntimeState *runtime)
return _PyStatus_OK();
}
-
static PyInterpreterState *
alloc_interpreter(void)
{
- return PyMem_RawCalloc(1, sizeof(PyInterpreterState));
+ size_t alignment = _Alignof(PyInterpreterState);
+ size_t allocsize = sizeof(PyInterpreterState) + 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;
}
static void
@@ -587,12 +595,15 @@ free_interpreter(PyInterpreterState *interp)
PyMem_RawFree(interp->obmalloc);
interp->obmalloc = NULL;
}
- PyMem_RawFree(interp);
+ assert(_Py_IS_ALIGNED(interp, _Alignof(PyInterpreterState)));
+ PyMem_RawFree(interp->_malloced);
}
}
+
#ifndef NDEBUG
static inline int check_interpreter_whence(long);
#endif
+
/* Get the interpreter state to a minimal consistent state.
Further init happens in pylifecycle.c before it can be used.
All fields not initialized here are expected to be zeroed out,
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