bpo-47260: Fix os.closerange() potentially being a no-op in a seccomp sandbox #32418
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… sandbox _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
gpshead
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Apr 8, 2022
gpshead
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needs backport to 3.10
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Sorry, @izbyshev and @gpshead, I could not cleanly backport this to |
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GH-32420 is a backport of this pull request to the 3.10 branch. |
miss-islington
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Apr 8, 2022
… sandbox (pythonGH-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 (cherry picked from commit 1c8b3b5) Co-authored-by: Alexey Izbyshev <izbyshev@ispras.ru>
miss-islington
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Apr 8, 2022
… 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 (cherry picked from commit 1c8b3b5) Co-authored-by: Alexey Izbyshev <izbyshev@ispras.ru>
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_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
https://bugs.python.org/issue47260