From 1c8b3b5d66a629258f1db16939b996264a8b9c37 Mon Sep 17 00:00:00 2001 From: Alexey Izbyshev Date: Fri, 8 Apr 2022 20:40:39 +0300 Subject: 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 --- .../NEWS.d/next/Library/2022-04-08-14-30-53.bpo-47260.TtcNxI.rst | 2 ++ Python/fileutils.c | 9 +++++---- 2 files changed, 7 insertions(+), 4 deletions(-) create mode 100644 Misc/NEWS.d/next/Library/2022-04-08-14-30-53.bpo-47260.TtcNxI.rst diff --git a/Misc/NEWS.d/next/Library/2022-04-08-14-30-53.bpo-47260.TtcNxI.rst b/Misc/NEWS.d/next/Library/2022-04-08-14-30-53.bpo-47260.TtcNxI.rst new file mode 100644 index 0000000..300baa1 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2022-04-08-14-30-53.bpo-47260.TtcNxI.rst @@ -0,0 +1,2 @@ +Fix ``os.closerange()`` potentially being a no-op in a Linux seccomp +sandbox. diff --git a/Python/fileutils.c b/Python/fileutils.c index 111d7fa..d1d62dc 100644 --- a/Python/fileutils.c +++ b/Python/fileutils.c @@ -2624,10 +2624,11 @@ _Py_closerange(int first, int last) first = Py_MAX(first, 0); _Py_BEGIN_SUPPRESS_IPH #ifdef HAVE_CLOSE_RANGE - if (close_range(first, last, 0) == 0 || errno != ENOSYS) { - /* Any errors encountered while closing file descriptors are ignored; - * ENOSYS means no kernel support, though, - * so we'll fallback to the other methods. */ + if (close_range(first, last, 0) == 0) { + /* close_range() ignores errors when it closes file descriptors. + * Possible reasons of an error return are lack of kernel support + * or denial of the underlying syscall by a seccomp sandbox on Linux. + * Fallback to other methods in case of any error. */ } else #endif /* HAVE_CLOSE_RANGE */ -- cgit v0.12