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bpo-41993: Fix possible issues in remove_module() (GH-22631) (GH-22647)

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* PyMapping_HasKey() is not safe because it silences all exceptions and can return incorrect result.
* Informative exceptions from PyMapping_DelItem() are overridden with RuntimeError and
  the original exception raised before calling remove_module() is lost.
* There is a race condition between PyMapping_HasKey() and PyMapping_DelItem().
(cherry picked from commit 8287aadb75)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
This commit is contained in:
Miss Skeleton (bot) 2020-10-14 02:09:44 -07:00 • committed by GitHub
parent 881a13cad5
commit 391a544f2a
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2 changed files with 15 additions and 10 deletions
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2
Misc/NEWS.d/next/Core and Builtins/2020-10-10-13-53-52.bpo-41993.YMzixQ.rst Normal file
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@ -0,0 +1,2 @@
Fixed potential issues with removing not completely initialized module from
``sys.modules`` when import fails.

23
Python/import.c
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@ -905,7 +905,11 @@ PyImport_AddModule(const char *name)
} }
/* Remove name from sys.modules, if it's there. */ /* Remove name from sys.modules, if it's there.
* Can be called with an exception raised.
* If fail to remove name a new exception will be chained with the old
* exception, otherwise the old exception is preserved.
*/
static void static void
remove_module(PyThreadState *tstate, PyObject *name) remove_module(PyThreadState *tstate, PyObject *name)
{ {
@ -913,18 +917,17 @@ remove_module(PyThreadState *tstate, PyObject *name)
_PyErr_Fetch(tstate, &type, &value, &traceback); _PyErr_Fetch(tstate, &type, &value, &traceback);
PyObject *modules = tstate->interp->modules; PyObject *modules = tstate->interp->modules;
if (!PyMapping_HasKey(modules, name)) { if (PyDict_CheckExact(modules)) {
goto out; PyObject *mod = _PyDict_Pop(modules, name, Py_None);
Py_XDECREF(mod);
} }
if (PyMapping_DelItem(modules, name) < 0) { else if (PyMapping_DelItem(modules, name) < 0) {
_PyErr_SetString(tstate, PyExc_RuntimeError, if (_PyErr_ExceptionMatches(tstate, PyExc_KeyError)) {
"deleting key in sys.modules failed"); _PyErr_Clear(tstate);
_PyErr_ChainExceptions(type, value, traceback); }
return;
} }
out: _PyErr_ChainExceptions(type, value, traceback);
_PyErr_Restore(tstate, type, value, traceback);
} }