bpo-30602: Fix refleak in os.spawnve() #2184
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When os.spawnve() fails while handling arguments, free correctly argvlist: pass lastarg+1 rather than lastarg to free_string_array() to also free the first item.
eryksun
reviewed
Jun 15, 2017
| @@ -5302,7 +5302,7 @@ os_spawnve_impl(PyObject *module, int mode, path_t *path, PyObject *argv, | |||
| PyMem_DEL(envlist[envc]); | |||
| PyMem_DEL(envlist); | |||
| fail_1: | |||
| free_string_array(argvlist, lastarg); | |||
| free_string_array(argvlist, lastarg + 1); | |||
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lastarg is set to i on line 5265 when fsconvert_strdup fails. Using lastarg + 1 in this case will free one too many pointers. It's also freeing one too many when all of argv is converted successfully and lastarg is set to argc. In this case argvlist[argc] is a NULL pointer, so freeing it is harmless.
I think the original code only needs a simple, single-line change. For the empty string case on line 5269. fsconvert_strdup has succeeded, so we know there's exactly lastarg = 1 pointer to free.
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When os.spawnve() fails while handling arguments, free correctly
argvlist: pass lastarg+1 rather than lastarg to free_string_array()
to also free the first item.