From fdd38cb16aea0aa44265a5b9395f8fe9bf56db7b Mon Sep 17 00:00:00 2001 From: Christian Heimes Date: Tue, 8 Mar 2022 11:34:41 +0100 Subject: [PATCH 1/4] bpo-23325: Fix SIG_IGN and SIG_DFL int comparison in signal module --- .../2022-03-08-11-34-06.bpo-23325.3VQnfo.rst | 2 ++ Modules/signalmodule.c | 34 ++++++++++++++----- 2 files changed, 28 insertions(+), 8 deletions(-) create mode 100644 Misc/NEWS.d/next/Library/2022-03-08-11-34-06.bpo-23325.3VQnfo.rst diff --git a/Misc/NEWS.d/next/Library/2022-03-08-11-34-06.bpo-23325.3VQnfo.rst b/Misc/NEWS.d/next/Library/2022-03-08-11-34-06.bpo-23325.3VQnfo.rst new file mode 100644 index 00000000000000..0801cbb4482256 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2022-03-08-11-34-06.bpo-23325.3VQnfo.rst @@ -0,0 +1,2 @@ +The :mod:`signal` module no longer assumes that :const:`~signal.SIG_IGN` and +:const:`~signal.SIG_DFL` are small int singletons. diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c index 26a1f48470ed23..20518bbd9a8217 100644 --- a/Modules/signalmodule.c +++ b/Modules/signalmodule.c @@ -496,6 +496,7 @@ signal_signal_impl(PyObject *module, int signalnum, PyObject *handler) _signal_module_state *modstate = get_signal_state(module); PyObject *old_handler; void (*func)(int); + int match = 0; // cannot use func == NULL as sentinel, SIG_DFL == 0 #ifdef MS_WINDOWS /* Validate that signalnum is one of the allowable signals */ switch (signalnum) { @@ -528,21 +529,38 @@ signal_signal_impl(PyObject *module, int signalnum, PyObject *handler) "signal number out of range"); return NULL; } - if (handler == modstate->ignore_handler) { - func = SIG_IGN; + if (PyCallable_Check(handler)) { + func = signal_handler; + match = 1; } - else if (handler == modstate->default_handler) { - func = SIG_DFL; + if (!match) { + int cmp = PyObject_RichCompareBool(handler, modstate->ignore_handler, Py_EQ); + switch (cmp) { + case -1: + return NULL; + case 1: + func = SIG_IGN; + match = 1; + break; + } } - else if (!PyCallable_Check(handler)) { + if (!match) { + int cmp = PyObject_RichCompareBool(handler, modstate->default_handler, Py_EQ); + switch (cmp) { + case -1: + return NULL; + case 1: + func = SIG_DFL; + match = 1; + break; + } + } + if (!match) { _PyErr_SetString(tstate, PyExc_TypeError, "signal handler must be signal.SIG_IGN, " "signal.SIG_DFL, or a callable object"); return NULL; } - else { - func = signal_handler; - } /* Check for pending signals before changing signal handler */ if (_PyErr_CheckSignalsTstate(tstate)) { From 34381041b9c92b78dfe7f76c3bca652b5a315597 Mon Sep 17 00:00:00 2001 From: Christian Heimes Date: Tue, 8 Mar 2022 12:32:05 +0100 Subject: [PATCH 2/4] Fix comparison in PyErr_SetInterruptEx() --- Modules/signalmodule.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c index 20518bbd9a8217..efe522517107ea 100644 --- a/Modules/signalmodule.c +++ b/Modules/signalmodule.c @@ -1911,7 +1911,15 @@ PyErr_SetInterruptEx(int signum) signal_state_t *state = &signal_global_state; PyObject *func = get_handler(signum); - if (func != state->ignore_handler && func != state->default_handler) { + int is_ign = PyObject_RichCompareBool(func, state->ignore_handler, Py_EQ); + if (is_ign == -1) { + return -1; + } + int is_dfl = PyObject_RichCompareBool(func, state->default_handler, Py_EQ); + if (is_dfl == -1) { + return -1; + } + if ((is_ign == 0) && (is_dfl == 0)) { trip_signal(signum); } return 0; From cc4df0594e134e262c8e9a5191f6a1fa20baeee8 Mon Sep 17 00:00:00 2001 From: Christian Heimes Date: Tue, 8 Mar 2022 17:27:26 +0100 Subject: [PATCH 3/4] Compare handler in a safe helper function --- Modules/signalmodule.c | 62 ++++++++++++++++-------------------------- 1 file changed, 23 insertions(+), 39 deletions(-) diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c index efe522517107ea..be42ddac08a18c 100644 --- a/Modules/signalmodule.c +++ b/Modules/signalmodule.c @@ -177,6 +177,17 @@ get_signal_state(PyObject *module) } +static inline int +compare_handler(PyObject *handler, PyObject *func) +{ + assert(PyLong_CheckExact(handler)); + if (!PyLong_CheckExact(func)) { + return 0; + } + // Assume that comparison of two PyLong objects will never fail. + return PyObject_RichCompareBool(func, handler, Py_EQ) == 1; +} + #ifdef HAVE_GETITIMER /* auxiliary functions for setitimer */ static int @@ -496,7 +507,6 @@ signal_signal_impl(PyObject *module, int signalnum, PyObject *handler) _signal_module_state *modstate = get_signal_state(module); PyObject *old_handler; void (*func)(int); - int match = 0; // cannot use func == NULL as sentinel, SIG_DFL == 0 #ifdef MS_WINDOWS /* Validate that signalnum is one of the allowable signals */ switch (signalnum) { @@ -531,31 +541,11 @@ signal_signal_impl(PyObject *module, int signalnum, PyObject *handler) } if (PyCallable_Check(handler)) { func = signal_handler; - match = 1; - } - if (!match) { - int cmp = PyObject_RichCompareBool(handler, modstate->ignore_handler, Py_EQ); - switch (cmp) { - case -1: - return NULL; - case 1: - func = SIG_IGN; - match = 1; - break; - } - } - if (!match) { - int cmp = PyObject_RichCompareBool(handler, modstate->default_handler, Py_EQ); - switch (cmp) { - case -1: - return NULL; - case 1: - func = SIG_DFL; - match = 1; - break; - } - } - if (!match) { + } else if (compare_handler(handler, modstate->ignore_handler)) { + func = SIG_IGN; + } else if (compare_handler(handler, modstate->default_handler)) { + func = SIG_DFL; + } else { _PyErr_SetString(tstate, PyExc_TypeError, "signal handler must be signal.SIG_IGN, " "signal.SIG_DFL, or a callable object"); @@ -1770,8 +1760,8 @@ _PySignal_Fini(void) set_handler(signum, NULL); if (func != NULL && func != Py_None - && func != state->default_handler - && func != state->ignore_handler) + && !compare_handler(func, state->default_handler) + && !compare_handler(func, state->ignore_handler)) { PyOS_setsig(signum, SIG_DFL); } @@ -1842,8 +1832,9 @@ _PyErr_CheckSignalsTstate(PyThreadState *tstate) * (see bpo-43406). */ PyObject *func = get_handler(i); - if (func == NULL || func == Py_None || func == state->ignore_handler || - func == state->default_handler) { + if (func == NULL || func == Py_None || + compare_handler(func, state->ignore_handler) || + compare_handler(func, state->default_handler)) { /* No Python signal handler due to aforementioned race condition. * We can't call raise() as it would break the assumption * that PyErr_SetInterrupt() only *simulates* an incoming @@ -1911,15 +1902,8 @@ PyErr_SetInterruptEx(int signum) signal_state_t *state = &signal_global_state; PyObject *func = get_handler(signum); - int is_ign = PyObject_RichCompareBool(func, state->ignore_handler, Py_EQ); - if (is_ign == -1) { - return -1; - } - int is_dfl = PyObject_RichCompareBool(func, state->default_handler, Py_EQ); - if (is_dfl == -1) { - return -1; - } - if ((is_ign == 0) && (is_dfl == 0)) { + if (!compare_handler(func, state->ignore_handler) + && !compare_handler(func, state->default_handler)) { trip_signal(signum); } return 0; From 76e31353d9bb373640b0baad187a0abd3ad5dfcf Mon Sep 17 00:00:00 2001 From: Christian Heimes Date: Tue, 8 Mar 2022 17:38:23 +0100 Subject: [PATCH 4/4] Use right order of arguments --- Modules/signalmodule.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c index be42ddac08a18c..9566263a0dd87e 100644 --- a/Modules/signalmodule.c +++ b/Modules/signalmodule.c @@ -178,14 +178,14 @@ get_signal_state(PyObject *module) static inline int -compare_handler(PyObject *handler, PyObject *func) +compare_handler(PyObject *func, PyObject *dfl_ign_handler) { - assert(PyLong_CheckExact(handler)); + assert(PyLong_CheckExact(dfl_ign_handler)); if (!PyLong_CheckExact(func)) { return 0; } // Assume that comparison of two PyLong objects will never fail. - return PyObject_RichCompareBool(func, handler, Py_EQ) == 1; + return PyObject_RichCompareBool(func, dfl_ign_handler, Py_EQ) == 1; } #ifdef HAVE_GETITIMER