bpo-45691: Make array of small ints static to fix use-after-free error. by markshannon · Pull Request #29366 · python/cpython · GitHub
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bpo-45691: Make array of small ints static to fix use-after-free error. #29366

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Merged
markshannon merged 2 commits into from
Nov 3, 2021
+31 −45
Merged

bpo-45691: Make array of small ints static to fix use-after-free error. #29366

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cf816d6
Make array of small ints static to fix use-after-free error.
markshannon Nov 2, 2021
9ee9157
Move small ints into runtime-state.
markshannon Nov 3, 2021
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14 changes: 0 additions & 14 deletions Include/internal/pycore_interp.h
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17 changes: 2 additions & 15 deletions Include/internal/pycore_long.h
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Original file line number Diff line number Diff line change
Expand Up @@ -11,28 +11,15 @@ extern "C" {
#include "pycore_interp.h" // PyInterpreterState.small_ints
#include "pycore_pystate.h" // _PyThreadState_GET()

// Don't call this function but _PyLong_GetZero() and _PyLong_GetOne()
static inline PyObject* __PyLong_GetSmallInt_internal(int value)
{
PyInterpreterState *interp = _PyInterpreterState_GET();
assert(-_PY_NSMALLNEGINTS <= value && value < _PY_NSMALLPOSINTS);
size_t index = _PY_NSMALLNEGINTS + value;
PyObject *obj = (PyObject*)&interp->small_ints[index];
// _PyLong_GetZero(), _PyLong_GetOne() and get_small_int() must not be
// called before _PyLong_Init() nor after _PyLong_Fini().
assert(obj != NULL);
return obj;
}

// Return a borrowed reference to the zero singleton.
// The function cannot return NULL.
static inline PyObject* _PyLong_GetZero(void)
{ return __PyLong_GetSmallInt_internal(0); }
{ return (PyObject *)&_PyRuntime.small_ints[_PY_NSMALLNEGINTS]; }

// Return a borrowed reference to the one singleton.
// The function cannot return NULL.
static inline PyObject* _PyLong_GetOne(void)
{ return __PyLong_GetSmallInt_internal(1); }
{ return (PyObject *)&_PyRuntime.small_ints[_PY_NSMALLNEGINTS+1]; }

PyObject *_PyLong_Add(PyLongObject *left, PyLongObject *right);
PyObject *_PyLong_Multiply(PyLongObject *left, PyLongObject *right);
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15 changes: 15 additions & 0 deletions Include/internal/pycore_runtime.h
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,14 @@ extern "C" {
#include "pycore_atomic.h" /* _Py_atomic_address */
#include "pycore_gil.h" // struct _gil_runtime_state

#define _PY_NSMALLPOSINTS 257
#define _PY_NSMALLNEGINTS 5

// _PyLong_GetZero() and _PyLong_GetOne() must always be available
#if _PY_NSMALLPOSINTS < 2
# error "_PY_NSMALLPOSINTS must be greater than 1"
#endif

/* ceval state */

struct _ceval_runtime_state {
Expand Down Expand Up @@ -100,6 +108,13 @@ typedef struct pyruntimestate {

unsigned long main_thread;

/* Small integers are preallocated in this array so that they
* can be shared.
* The integers that are preallocated are those in the range
*-_PY_NSMALLNEGINTS (inclusive) to _PY_NSMALLPOSINTS (not inclusive).
*/
PyLongObject small_ints[_PY_NSMALLNEGINTS + _PY_NSMALLPOSINTS];

#define NEXITFUNCS 32
void (*exitfuncs[NEXITFUNCS])(void);
int nexitfuncs;
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30 changes: 14 additions & 16 deletions Objects/longobject.c
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