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bpo-33191: Fix refleak in posix_spawn #6315

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bpo-33191: Fix refleak in posix_spawn #6315

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16c332f
bpo-33191: Fix refleak in posix_spawn
zware Mar 30, 2018
452479b
Add blurb
zware Mar 30, 2018
775649f
mention the os module
gpshead Mar 30, 2018
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core and Builtins/2018-03-30-16-13-01.bpo-33191.P143W_.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fixed a refleak in os.posix_spawn.
28 changes: 16 additions & 12 deletions Modules/posixmodule.c
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Expand Up @@ -5142,6 +5142,7 @@ os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
Py_ssize_t argc, envc;
PyObject* result = NULL;
PyObject* seq = NULL;
PyObject* file_actions_obj = NULL;


/* posix_spawn has three arguments: (path, argv, env), where
Expand Down Expand Up @@ -5194,17 +5195,17 @@ os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
if(seq == NULL) {
goto exit;
}
PyObject* file_actions_obj;
PyObject* mode_obj;

for (int i = 0; i < PySequence_Fast_GET_SIZE(seq); ++i) {
file_actions_obj = PySequence_Fast_GET_ITEM(seq, i);

if(!PySequence_Check(file_actions_obj) | !PySequence_Size(file_actions_obj)) {
PyErr_SetString(PyExc_TypeError,"Each file_action element must be a non empty sequence");
if (file_actions_obj == NULL) {
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@serhiy-storchaka serhiy-storchaka Mar 31, 2018

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Is it possible?

goto exit;
}
file_actions_obj = PySequence_Fast(file_actions_obj, "Each file_action element must be a non-empty sequence");
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@serhiy-storchaka serhiy-storchaka Mar 31, 2018

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Would be nice to wrap this long line.

if (file_actions_obj == NULL) {
goto exit;
}


mode_obj = PySequence_Fast_GET_ITEM(file_actions_obj, 0);
int mode = PyLong_AsLong(mode_obj);
Expand All @@ -5219,19 +5220,19 @@ os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
goto exit;
}

long open_fd = PyLong_AsLong(PySequence_GetItem(file_actions_obj, 1));
long open_fd = PyLong_AsLong(PySequence_Fast_GET_ITEM(file_actions_obj, 1));
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@serhiy-storchaka serhiy-storchaka Mar 31, 2018

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PyLong_AsLong() can call arbitrary code. If file_actions is a list, the size of file_actions_obj can be changed after this, and the following PySequence_Fast_GET_ITEM() could read past the end of the list.

I would require file_actions to be a tuple and use PyArg_ParseTuple() for parsing it.

if(PyErr_Occurred()) {
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@serhiy-storchaka serhiy-storchaka Mar 31, 2018

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While you are here, could you please make the source conforming PEP 7: Add spaces after "if" and "switch", wrap long lines?

goto exit;
}
const char* open_path = PyUnicode_AsUTF8(PySequence_GetItem(file_actions_obj, 2));
const char* open_path = PyUnicode_AsUTF8(PySequence_Fast_GET_ITEM(file_actions_obj, 2));
if(open_path == NULL) {
goto exit;
}
long open_oflag = PyLong_AsLong(PySequence_GetItem(file_actions_obj, 3));
long open_oflag = PyLong_AsLong(PySequence_Fast_GET_ITEM(file_actions_obj, 3));
if(PyErr_Occurred()) {
goto exit;
}
long open_mode = PyLong_AsLong(PySequence_GetItem(file_actions_obj, 4));
long open_mode = PyLong_AsLong(PySequence_Fast_GET_ITEM(file_actions_obj, 4));
if(PyErr_Occurred()) {
goto exit;
}
Expand All @@ -5248,7 +5249,7 @@ os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
goto exit;
}

long close_fd = PyLong_AsLong(PySequence_GetItem(file_actions_obj, 1));
long close_fd = PyLong_AsLong(PySequence_Fast_GET_ITEM(file_actions_obj, 1));
if(PyErr_Occurred()) {
goto exit;
}
Expand All @@ -5264,11 +5265,11 @@ os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
goto exit;
}

long fd1 = PyLong_AsLong(PySequence_GetItem(file_actions_obj, 1));
long fd1 = PyLong_AsLong(PySequence_Fast_GET_ITEM(file_actions_obj, 1));
if(PyErr_Occurred()) {
goto exit;
}
long fd2 = PyLong_AsLong(PySequence_GetItem(file_actions_obj, 2));
long fd2 = PyLong_AsLong(PySequence_Fast_GET_ITEM(file_actions_obj, 2));
if(PyErr_Occurred()) {
goto exit;
}
Expand All @@ -5282,7 +5283,9 @@ os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
PyErr_SetString(PyExc_TypeError,"Unknown file_actions identifier");
goto exit;
}
Py_DECREF(file_actions_obj);
}
file_actions_obj = NULL;
}

_Py_BEGIN_SUPPRESS_IPH
Expand All @@ -5297,6 +5300,7 @@ os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
exit:

Py_XDECREF(seq);
Py_XDECREF(file_actions_obj);

if(file_actionsp) {
posix_spawn_file_actions_destroy(file_actionsp);
Expand Down