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bpo-1635741: Fix potential refleaks in binascii module #18613

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Merged
merged 2 commits into from
Mar 11, 2020
Merged

bpo-1635741: Fix potential refleaks in binascii module #18613

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3a3274a
Fix potential refleaks in binascii module
shihai1991 Feb 23, 2020
a2f1f99
using the var name module to replace m
shihai1991 Mar 1, 2020
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46 changes: 43 additions & 3 deletions 46 Modules/binascii.c
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,12 @@ typedef struct binascii_state {
PyObject *Incomplete;
} binascii_state;

static binascii_state *
get_binascii_state(PyObject *module)
{
return (binascii_state *)PyModule_GetState(module);
}

/*
** hqx lookup table, ascii->binary.
*/
Expand Down Expand Up @@ -1617,17 +1623,21 @@ binascii_exec(PyObject *m) {
if (state->Error == NULL) {
return -1;
}
Py_INCREF(state->Error);
result = PyModule_AddObject(m, "Error", state->Error);
if (result == -1) {
Py_DECREF(state->Error);
return -1;
}

state->Incomplete = PyErr_NewException("binascii.Incomplete", NULL, NULL);
if (state->Incomplete == NULL) {
return -1;
}
Py_INCREF(state->Incomplete);
result = PyModule_AddObject(m, "Incomplete", state->Incomplete);
if (result == -1) {
Py_DECREF(state->Incomplete);
return -1;
}

Expand All @@ -1639,16 +1649,46 @@ static PyModuleDef_Slot binascii_slots[] = {
{0, NULL}
};

static int
binascii_traverse(PyObject *m, visitproc visit, void *arg)
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nitpick: I would prefer to use longer variable name than just "m". Rename "m" to "mod" or "module". Same remark if following functions.

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ok, no probleam, i will update it.

{
binascii_state *state = get_binascii_state(m);
if (state == NULL) {
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I will update this behavior soon.

return -1;
}
Py_VISIT(state->Error);
Py_VISIT(state->Incomplete);
return 0;
}

static int
binascii_clear(PyObject *m)
{
binascii_state *state = get_binascii_state(m);
if (state == NULL) {
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I don't think that state can be NULL. If it's NULL, it's a bug in Python. No? Same remark in binascii_traverse().

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I do some debug in my vm:

Breakpoint 1, binascii_traverse (module=0x7ffff7e803d0, visit=0x4630b6 <bad_traverse_test>, arg=0x0) at /temp/shihai/cpython/Modules/binascii.c:1654
1654    {
(gdb) n
1655        binascii_state *state = get_binascii_state(module);
(gdb) n
1656        if (state == NULL) {
(gdb) n
1657            return -1;
(gdb) p state
$5 = (binascii_state *) 0x0
(gdb) c
Continuing.

Breakpoint 3, binascii_exec (module=0x7ffff7e803d0) at /temp/shihai/cpython/Modules/binascii.c:1615
1615    binascii_exec(PyObject *module) {

What's the reason?
the malloc operation of md_state will be called after first calling binascii_traverse.
https://github.com/python/cpython/blob/master/Objects/moduleobject.c#L399.

return -1;
}
Py_CLEAR(state->Error);
Py_CLEAR(state->Incomplete);
return 0;
}

static void
binascii_free(void *m)
{
binascii_clear((PyObject *)m);
}

static struct PyModuleDef binasciimodule = {
PyModuleDef_HEAD_INIT,
"binascii",
doc_binascii,
sizeof(binascii_state),
binascii_module_methods,
binascii_slots,
NULL,
NULL,
NULL
binascii_traverse,
binascii_clear,
binascii_free
};

PyMODINIT_FUNC
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