[issue25631] Segmentation fault with invalid Unicode command-line arguments in embedded Python

[STINNER Victor]

STINNER Victor  added the comment:

This bug has been fixed in the implementation of the PEP 587.

$ gcc x.c -l python3.8 $(pkg-config python-3.8 --cflags --libs) -o x
$ ./x
Fatal Python error: pyinit_main: can't finish initializing sys
ValueError: character U+11 is not in range [U+; U+10]

Current thread 0x7fd23364e6c0 (most recent call first):

=> it doesn't crash anymore, but write a error message and exit.

--
nosy: +vstinner
resolution:  -> fixed
stage:  -> resolved
status: open -> closed
versions: +Python 3.8, Python 3.9 -Python 3.4, Python 3.5, Python 3.6

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[issue25631] Segmentation fault with invalid Unicode command-line arguments in embedded Python

[Eryk Sun]

Eryk Sun added the comment:

The interpreter isn't initialized, so calling PyErr_Format in a release build 
segfaults when it tries to dereference a NULL PyThreadState. OTOH, a debug 
build should call PyThreadState_Get, which in this case calls Py_FatalError and 
aborts the process. Unfortunately 3.5.0+ debug builds don't call 
PyThreadState_Get due to the fix for issue 25150.

> the possibility of other exceptions being raised early in the 
> initialization sequence remains a potential problem.

PEP 432 proposes a pre-initialization phase that sets a valid Python thread 
state.

--
nosy: +eryksun, ncoghlan

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[issue25631] Segmentation fault with invalid Unicode command-line arguments in embedded Python

[Itai Bar-Natan]

New submission from Itai Bar-Natan:

The following embedded application, which calls Py_Main with a "-W X" argument 
where X is not a valid Unicode string, returns a segmentation fault:

```
#include "Python.h"

main() {
wchar_t *invalid_str;
invalid_str = malloc(2*sizeof(wchar_t));
invalid_str[0] = 0x11;
invalid_str[1] = 0;
wchar_t *argv[4] = {L"embedded-python", L"-W", invalid_str, NULL};

Py_Main(3, argv);
}
```

This segmentation fault is present in Python 3.4, 3.5, and the latest 
development branch I downloaded, but is not present in Python 3.2. This program 
is obviously invalid and it may be reasonable to emit a fatal error in this 
situation, but it should not give a segmentation fault.

I believe the issue is that this codes leads to exception being thrown before 
exceptions are initialized, and more specifically, a call to 
PyExceptionClass_Check() within PyErr_Object() reads a NULL pointer. I haven't 
tested this but I expect that this problem would not appear when calling Python 
directly since Python sanitizes the command line arguments from main(). 
Nonetheless even here the possibility of other exceptions being raised early in 
the initialization sequence remains a potential problem.

--
components: Interpreter Core
messages: 254703
nosy: itaibn
priority: normal
severity: normal
status: open
title: Segmentation fault with invalid Unicode command-line arguments in 
embedded Python
type: crash
versions: Python 3.4, Python 3.5, Python 3.6

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