Skip to content

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

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 8 commits into from
Apr 2, 2025
+83 −16
Merged

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

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
8 commits
Select commit Hold shift + click to select a range
0a27451
Fix usages of locked_deref()
ZeroIntensity Apr 1, 2025
e2a4ea0
Add blurb entry.
ZeroIntensity Apr 1, 2025
22004fb
Pass len to copy_pointer_to_list_lock_held()
ZeroIntensity Apr 1, 2025
8f52814
Fix wchar_t dereferences.
ZeroIntensity Apr 1, 2025
011c747
Update Modules/_ctypes/_ctypes.c
ZeroIntensity Apr 2, 2025
c31a405
Revert "Update Modules/_ctypes/_ctypes.c"
ZeroIntensity Apr 2, 2025
7a44c77
Only lock if we're not self.
ZeroIntensity Apr 2, 2025
9648678
Add the lock.
ZeroIntensity Apr 2, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2025-04-01-09-20-32.gh-issue-131974.AIzshA.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix several thread-safety issues in :mod:`ctypes` on the :term:`free
threaded <free threading>` build.
97 changes: 81 additions & 16 deletions Modules/_ctypes/_ctypes.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

You may add a deref_lock_held() function for this operation.

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Eh, I don't think its necessary. A dereference is easy enough to write.


if (deref == NULL) {
PyErr_SetString(PyExc_ValueError,
Expand Down Expand Up @@ -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;
Expand All @@ -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");
Expand Down Expand Up @@ -5409,10 +5424,21 @@ Pointer_ass_item(PyObject *myself, Py_ssize_t index, PyObject *value)
index, size, ((char *)deref + offset));
}

static int
Pointer_ass_item(PyObject *myself, Py_ssize_t index, PyObject *value)
{
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(PyObject *self, void *closure)
Pointer_get_contents_lock_held(PyObject *self, void *closure)
{
void *deref = locked_deref(_CDataObject_CAST(self));
void *deref = *(void **)_CDataObject_CAST(self)->b_ptr;
if (deref == NULL) {
PyErr_SetString(PyExc_ValueError,
"NULL pointer access");
Expand All @@ -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)
{
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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)
{
Expand Down Expand Up @@ -5595,14 +5657,14 @@ 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)
return Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
if (step == 1) {
PyObject *res;
LOCK_PTR(self);
char *ptr = *(void **)self->b_ptr;
res = PyBytes_FromStringAndSize(ptr + start,
len);
UNLOCK_PTR(self);
Expand All @@ -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];
}
Expand All @@ -5621,14 +5684,14 @@ 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)
return Py_GetConstant(Py_CONSTANT_EMPTY_STR);
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);
Expand All @@ -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];
}
Expand All @@ -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 {
Expand Down
Loading