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[3.7] bpo-22689: Copy the result of getenv() in sys_breakpointhook(). (GH-8194) #8206

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Merged
miss-islington merged 1 commit into from
Jul 9, 2018
Merged

[3.7] bpo-22689: Copy the result of getenv() in sys_breakpointhook(). (GH-8194) #8206

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15 changes: 14 additions & 1 deletion Python/sysmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -107,7 +107,7 @@ static PyObject *
sys_breakpointhook(PyObject *self, PyObject *const *args, Py_ssize_t nargs, PyObject *keywords)
{
assert(!PyErr_Occurred());
const char *envar = Py_GETENV("PYTHONBREAKPOINT");
char *envar = Py_GETENV("PYTHONBREAKPOINT");

if (envar == NULL || strlen(envar) == 0) {
envar = "pdb.set_trace";
Expand All @@ -116,6 +116,15 @@ sys_breakpointhook(PyObject *self, PyObject *const *args, Py_ssize_t nargs, PyOb
/* The breakpoint is explicitly no-op'd. */
Py_RETURN_NONE;
}
/* According to POSIX the string returned by getenv() might be invalidated
* or the string content might be overwritten by a subsequent call to
* getenv(). Since importing a module can performs the getenv() calls,
* we need to save a copy of envar. */
envar = _PyMem_RawStrdup(envar);
if (envar == NULL) {
PyErr_NoMemory();
return NULL;
}
const char *last_dot = strrchr(envar, '.');
const char *attrname = NULL;
PyObject *modulepath = NULL;
Expand All @@ -131,12 +140,14 @@ sys_breakpointhook(PyObject *self, PyObject *const *args, Py_ssize_t nargs, PyOb
attrname = last_dot + 1;
}
if (modulepath == NULL) {
PyMem_RawFree(envar);
return NULL;
}

PyObject *fromlist = Py_BuildValue("(s)", attrname);
if (fromlist == NULL) {
Py_DECREF(modulepath);
PyMem_RawFree(envar);
return NULL;
}
PyObject *module = PyImport_ImportModuleLevelObject(
Expand All @@ -154,6 +165,7 @@ sys_breakpointhook(PyObject *self, PyObject *const *args, Py_ssize_t nargs, PyOb
if (hook == NULL) {
goto error;
}
PyMem_RawFree(envar);
PyObject *retval = _PyObject_FastCallKeywords(hook, args, nargs, keywords);
Py_DECREF(hook);
return retval;
Expand All @@ -164,6 +176,7 @@ sys_breakpointhook(PyObject *self, PyObject *const *args, Py_ssize_t nargs, PyOb
int status = PyErr_WarnFormat(
PyExc_RuntimeWarning, 0,
"Ignoring unimportable $PYTHONBREAKPOINT: \"%s\"", envar);
PyMem_RawFree(envar);
if (status < 0) {
/* Printing the warning raised an exception. */
return NULL;
Expand Down