sys.excepthook (PyErr_Display) does crash with SyntaxError which has a bytes filename #81648
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Using attached sf.py and sf.xml, I can crash Python. lxml builds a fake traceback to inject the XML filename the XML line number where the parsing error occurs. The problem is that the filename is a bytes object, whereas print_exception() expects the filename to be a Unicode string. Attached PR fix the crash. Fedora bug report: Example: $ python3 sf.py
<lxml.etree._ElementTree object at 0x7f7d0f8abd08>
Traceback (most recent call last):
File "sf.py", line 6, in <module>
xml2 = etree.parse("sf.xml")
File "src/lxml/etree.pyx", line 3426, in lxml.etree.parse
File "src/lxml/parser.pxi", line 1840, in lxml.etree._parseDocument
File "src/lxml/parser.pxi", line 1866, in lxml.etree._parseDocumentFromURL
File "src/lxml/parser.pxi", line 1770, in lxml.etree._parseDocFromFile
File "src/lxml/parser.pxi", line 1163, in lxml.etree._BaseParser._parseDocFromFile
File "src/lxml/parser.pxi", line 601, in lxml.etree._ParserContext._handleParseResultDoc
File "src/lxml/parser.pxi", line 711, in lxml.etree._handleParseResult
File "src/lxml/parser.pxi", line 651, in lxml.etree._raiseParseError
Segmentation fault (core dumped)(gdb) frame 6 Extract of print_exception(): PyObject *message, *filename, *text;
int lineno, offset;
if (!parse_syntax_error(value, &message, &filename,
&lineno, &offset, &text))
PyErr_Clear();
else {
PyObject *line;
Py_DECREF(value);
value = message;
line = PyUnicode_FromFormat(" File \"%S\", line %d\n", // <====== HERE
filename, lineno);
Py_DECREF(filename);More gdb traceback: Program received signal SIGSEGV, Segmentation fault. |
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3.7 (EOL)
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The bug can be reproduced on the master branch of Python. I tested with versions:
The filename comes from a lxml.etree.XMLSyntaxError exception which inherits from SyntaxError. The bug can be reproduced without lxml nor xmlsec, just with attached excepthook_syntaxerror.py: $ ./python excepthook_syntaxerror.py
Traceback (most recent call last):
File "/home/vstinner/prog/python/master/excepthook_syntaxerror.py", line 3, in <module>
raise SyntaxError("msg", (b"bytes_filename", 123, 0, "text"))
Objects/unicodeobject.c:492: _PyUnicode_CheckConsistency: Assertion "((((((PyObject*)(op))->ob_type))->tp_flags & ((1UL << 28))) != 0)" failed
Enable tracemalloc to get the memory block allocation tracebackobject : b'bytes_filename' Current thread 0x00007fe23cfbf740 (most recent call first): excepthook_syntaxerror.py uses: raise SyntaxError("msg", (b"bytes_filename", 123, 0, "text")) |
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Python 2.7 is not affected: const char *filename, *text;
int lineno, offset;
if (!parse_syntax_error(value, &message, &filename,
&lineno, &offset, &text))
PyErr_Clear();
else {
char buf[10];
PyFile_WriteString(" File \"", f);
if (filename == NULL)
PyFile_WriteString("<string>", f);
else
PyFile_WriteString(filename, f);
PyFile_WriteString("\", line ", f);
PyOS_snprintf(buf, sizeof(buf), "%d", lineno);
PyFile_WriteString(buf, f);
PyFile_WriteString("\n", f); |
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Ok, it's not fixed in all affected maintained branches, I close the issue. |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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