`fixfiles -M relabel` temporary bind mounts file systems before
relabeling, but it left the / directory mounted in /tmp/tmp.XXXX when a
user hit CTRL-C. It means that if the user run `fixfiles -M relabel`
again and answered Y to clean out /tmp directory, it would remove all
data from mounted fs.
This patch changes the location where `fixfiles` mounts fs to /run, uses
private mount namespace via unshare and adds a handler for exit signals
which tries to umount fs mounted by `fixfiles`.
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2125355
Signed-off-by: Petr Lautrbach <plautrba@redhat.com>
Tested-by: Christian Göttsche <cgzones@googlemail.com>
Acked-by: James Carter <jwcart2@gmail.com>
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