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gh-131974: Fix usages of locked_deref in ctypes (#131975)

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Peter Bierma 2025-04-02 11:04:25 -04:00 • committed by GitHub
parent 25275bda79
commit 6e91d1f9aa
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2 changed files with 84 additions and 17 deletions
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2
Misc/NEWS.d/next/Library/2025-04-01-09-20-32.gh-issue-131974.AIzshA.rst Normal file
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@ -0,0 +1,2 @@
Fix several thread-safety issues in :mod:`ctypes` on the :term:`free
threaded <free threading>` build.

99
Modules/_ctypes/_ctypes.c
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@ -5326,13 +5326,13 @@ static PyType_Spec pycsimple_spec = {
PyCPointer_Type
*/
static PyObject *
Pointer_item(PyObject *myself, Py_ssize_t index)
Pointer_item_lock_held(PyObject *myself, Py_ssize_t index)
{
CDataObject *self = _CDataObject_CAST(myself);
Py_ssize_t size;
Py_ssize_t offset;
PyObject *proto;
void *deref = locked_deref(self);
void *deref = *(void **)self->b_ptr;
if (deref == NULL) {
PyErr_SetString(PyExc_ValueError,
@ -5364,8 +5364,23 @@ Pointer_item(PyObject *myself, Py_ssize_t index)
index, size, (char *)((char *)deref + offset));
}
static PyObject *
Pointer_item(PyObject *myself, Py_ssize_t index)
{
CDataObject *self = _CDataObject_CAST(myself);
PyObject *res;
// TODO: The plan is to make LOCK_PTR() a mutex instead of a critical
// section someday, so when that happens, this needs to get refactored
// to be re-entrant safe.
// This goes for all the locks here.
LOCK_PTR(self);
res = Pointer_item_lock_held(myself, index);
UNLOCK_PTR(self);
return res;
}
static int
Pointer_ass_item(PyObject *myself, Py_ssize_t index, PyObject *value)
Pointer_ass_item_lock_held(PyObject *myself, Py_ssize_t index, PyObject *value)
{
CDataObject *self = _CDataObject_CAST(myself);
Py_ssize_t size;
@ -5378,7 +5393,7 @@ Pointer_ass_item(PyObject *myself, Py_ssize_t index, PyObject *value)
return -1;
}
void *deref = locked_deref(self);
void *deref = *(void **)self->b_ptr;
if (deref == NULL) {
PyErr_SetString(PyExc_ValueError,
"NULL pointer access");
@ -5409,10 +5424,21 @@ Pointer_ass_item(PyObject *myself, Py_ssize_t index, PyObject *value)
index, size, ((char *)deref + offset));
}
static PyObject *
Pointer_get_contents(PyObject *self, void *closure)
static int
Pointer_ass_item(PyObject *myself, Py_ssize_t index, PyObject *value)
{
void *deref = locked_deref(_CDataObject_CAST(self));
CDataObject *self = _CDataObject_CAST(myself);
int res;
LOCK_PTR(self);
res = Pointer_ass_item_lock_held(myself, index, value);
UNLOCK_PTR(self);
return res;
}
static PyObject *
Pointer_get_contents_lock_held(PyObject *self, void *closure)
{
void *deref = *(void **)_CDataObject_CAST(self)->b_ptr;
if (deref == NULL) {
PyErr_SetString(PyExc_ValueError,
"NULL pointer access");
@ -5429,6 +5455,17 @@ Pointer_get_contents(PyObject *self, void *closure)
return PyCData_FromBaseObj(st, stginfo->proto, self, 0, deref);
}
static PyObject *
Pointer_get_contents(PyObject *myself, void *closure)
{
CDataObject *self = _CDataObject_CAST(myself);
PyObject *res;
LOCK_PTR(self);
res = Pointer_get_contents_lock_held(myself, closure);
UNLOCK_PTR(self);
return res;
}
static int
Pointer_set_contents(PyObject *op, PyObject *value, void *closure)
{
@ -5462,7 +5499,15 @@ Pointer_set_contents(PyObject *op, PyObject *value, void *closure)
}
dst = (CDataObject *)value;
locked_deref_assign(self, dst->b_ptr);
if (dst != self) {
LOCK_PTR(dst);
locked_deref_assign(self, dst->b_ptr);
UNLOCK_PTR(dst);
} else {
LOCK_PTR(self);
*((void **)self->b_ptr) = dst->b_ptr;
UNLOCK_PTR(self);
}
/*
A Pointer instance must keep the value it points to alive. So, a
@ -5514,6 +5559,23 @@ Pointer_new(PyTypeObject *type, PyObject *args, PyObject *kw)
return generic_pycdata_new(st, type, args, kw);
}
static int
copy_pointer_to_list_lock_held(PyObject *myself, PyObject *np, Py_ssize_t len,
Py_ssize_t start, Py_ssize_t step)
{
Py_ssize_t i;
size_t cur;
for (cur = start, i = 0; i < len; cur += step, i++) {
PyObject *v = Pointer_item_lock_held(myself, cur);
if (!v) {
return -1;
}
PyList_SET_ITEM(np, i, v);
}
return 0;
}
static PyObject *
Pointer_subscript(PyObject *myself, PyObject *item)
{
@ -5595,7 +5657,6 @@ Pointer_subscript(PyObject *myself, PyObject *item)
}
assert(iteminfo);
if (iteminfo->getfunc == _ctypes_get_fielddesc("c")->getfunc) {
char *ptr = locked_deref(self);
char *dest;
if (len <= 0)
@ -5603,6 +5664,7 @@ Pointer_subscript(PyObject *myself, PyObject *item)
if (step == 1) {
PyObject *res;
LOCK_PTR(self);
char *ptr = *(void **)self->b_ptr;
res = PyBytes_FromStringAndSize(ptr + start,
len);
UNLOCK_PTR(self);
@ -5612,6 +5674,7 @@ Pointer_subscript(PyObject *myself, PyObject *item)
if (dest == NULL)
return PyErr_NoMemory();
LOCK_PTR(self);
char *ptr = *(void **)self->b_ptr;
for (cur = start, i = 0; i < len; cur += step, i++) {
dest[i] = ptr[cur];
}
@ -5621,7 +5684,6 @@ Pointer_subscript(PyObject *myself, PyObject *item)
return np;
}
if (iteminfo->getfunc == _ctypes_get_fielddesc("u")->getfunc) {
wchar_t *ptr = locked_deref(self);
wchar_t *dest;
if (len <= 0)
@ -5629,6 +5691,7 @@ Pointer_subscript(PyObject *myself, PyObject *item)
if (step == 1) {
PyObject *res;
LOCK_PTR(self);
wchar_t *ptr = *(wchar_t **)self->b_ptr;
res = PyUnicode_FromWideChar(ptr + start,
len);
UNLOCK_PTR(self);
@ -5638,6 +5701,7 @@ Pointer_subscript(PyObject *myself, PyObject *item)
if (dest == NULL)
return PyErr_NoMemory();
LOCK_PTR(self);
wchar_t *ptr = *(wchar_t **)self->b_ptr;
for (cur = start, i = 0; i < len; cur += step, i++) {
dest[i] = ptr[cur];
}
@ -5651,14 +5715,15 @@ Pointer_subscript(PyObject *myself, PyObject *item)
if (np == NULL)
return NULL;
for (cur = start, i = 0; i < len; cur += step, i++) {
PyObject *v = Pointer_item(myself, cur);
if (!v) {
Py_DECREF(np);
return NULL;
}
PyList_SET_ITEM(np, i, v);
int res;
LOCK_PTR(self);
res = copy_pointer_to_list_lock_held(myself, np, len, start, step);
UNLOCK_PTR(self);
if (res < 0) {
Py_DECREF(np);
return NULL;
}
return np;
}
else {