gh-136062: Buffer Overflow Vulnerability in _Py_wreadlink Function #136064
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picnixz
reviewed
Jun 28, 2025
| @@ -2102,7 +2102,8 @@ _Py_wreadlink(const wchar_t *path, wchar_t *buf, size_t buflen) | |||
| errno = EINVAL; | |||
| return -1; | |||
| } | |||
| wcsncpy(buf, wbuf, buflen); | |||
| wcsncpy(buf, wbuf, buflen - 1); | |||
| buf[buflen - 1] = L'\0'; /* Ensure null termination */ | |||
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As I said, it's not necessary because wcsncpy copies the NUL termination if it's counted in buflen (which is the case because buflen > r1 == len(buf_without_NUL). And wcsncpy just fills the remaining chars with NUL chars:
If, after copying the terminating null wide character from src, count is not reached, additional null wide characters are written to dest until the total of count characters have been written.
So we'll anyway have a NUL termination.
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