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gh-132399: ensure correct alignment of PyInterpreterState when UBSan is on #132428

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Merged
merged 6 commits into from
Apr 19, 2025
Merged

gh-132399: ensure correct alignment of PyInterpreterState when UBSan is on #132428

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6455ebd
ensure correct alignment of PyInterpreterState when UBSan is on
picnixz Apr 12, 2025
239bfbd
Update Python/pystate.c
picnixz Apr 12, 2025
abb1af7
Remove redundant `inline` keyword
picnixz Apr 17, 2025
9cb710d
unconditionally align `PyInterpreterState`
picnixz Apr 18, 2025
8bd8f22
use `void *` instead of `uintptr_t`
picnixz Apr 18, 2025
12032df
Apply suggestions from code review
picnixz Apr 18, 2025
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3 changes: 3 additions & 0 deletions Include/pyport.h
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Original file line number Diff line number Diff line change
Expand Up @@ -664,14 +664,17 @@ extern "C" {
#if defined(__has_feature)
# if __has_feature(undefined_behavior_sanitizer)
# define _Py_NO_SANITIZE_UNDEFINED __attribute__((no_sanitize("undefined")))
# define _Py_HAS_UNDEFINED_BEHAVIOR_SANITIZER
# endif
#endif
#if !defined(_Py_NO_SANITIZE_UNDEFINED) && defined(__GNUC__) \
&& ((__GNUC__ >= 5) || (__GNUC__ == 4) && (__GNUC_MINOR__ >= 9))
# define _Py_NO_SANITIZE_UNDEFINED __attribute__((no_sanitize_undefined))
# define _Py_HAS_UNDEFINED_BEHAVIOR_SANITIZER
#endif
#ifndef _Py_NO_SANITIZE_UNDEFINED
# define _Py_NO_SANITIZE_UNDEFINED
# undef _Py_HAS_UNDEFINED_BEHAVIOR_SANITIZER
#endif


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32 changes: 31 additions & 1 deletion Python/pystate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -569,11 +569,28 @@ _PyInterpreterState_Enable(_PyRuntimeState *runtime)
return _PyStatus_OK();
}

#ifdef _Py_HAS_UNDEFINED_BEHAVIOR_SANITIZER
#define RAW_ALIGN_PTR_OFFSET sizeof(void *)
#endif

static PyInterpreterState *
static inline PyInterpreterState *
alloc_interpreter(void)
{
#ifdef _Py_HAS_UNDEFINED_BEHAVIOR_SANITIZER
size_t statesize = sizeof(PyInterpreterState);
size_t alignment = _Alignof(PyInterpreterState);
size_t allocsize = statesize + alignment - 1 + RAW_ALIGN_PTR_OFFSET;
void *mem = PyMem_RawCalloc(1, allocsize);
if (mem == NULL) {
return NULL;
}
char *interp = _Py_ALIGN_UP((char *)mem + RAW_ALIGN_PTR_OFFSET, alignment);
*(void **)(interp - RAW_ALIGN_PTR_OFFSET) = mem;
assert(_Py_IS_ALIGNED(interp, alignment));
return (PyInterpreterState *)interp;
#else
return PyMem_RawCalloc(1, sizeof(PyInterpreterState));
#endif
}

static void
Expand All @@ -587,12 +604,25 @@ free_interpreter(PyInterpreterState *interp)
PyMem_RawFree(interp->obmalloc);
interp->obmalloc = NULL;
}
#ifdef _Py_HAS_UNDEFINED_BEHAVIOR_SANITIZER
assert(_Py_IS_ALIGNED(interp, _Alignof(PyInterpreterState)));
char *mem_location = (char *)interp - RAW_ALIGN_PTR_OFFSET;
void *mem = *((void **)mem_location);
PyMem_RawFree(mem);
#else
PyMem_RawFree(interp);
#endif
}
}

#ifdef _Py_HAS_UNDEFINED_BEHAVIOR_SANITIZER
#undef RAW_ALIGN_PTR_OFFSET
#endif

#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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