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bpo-47260: Fix os.closerange() potentially being a no-op in a seccomp sandbox (GH-32418)

_Py_closerange() currently assumes that close_range() closes
all file descriptors even if it returns an error (other than ENOSYS).
This assumption can be wrong on Linux if a seccomp sandbox denies
the underlying syscall, pretending that it returns EPERM or EACCES.
In this case _Py_closerange() won't close any descriptors at all,
which in the worst case can be a security issue.

Fix this by falling back to other methods in case of any close_range()
error. Note that fallbacks will not be triggered on any problems with
closing individual file descriptors because close_range() is documented
to ignore such errors on both Linux[1] and FreeBSD[2].

[1] https://man7.org/linux/man-pages/man2/close_range.2.html
[2] https://www.freebsd.org/cgi/man.cgi?query=close_range&sektion=2
A
Alexey Izbyshev committed
1c8b3b5d66a629258f1db16939b996264a8b9c37
Parent: d6fb104
Committed by GitHub <noreply@github.com> on 4/8/2022, 5:40:39 PM