Red Hat Bugzilla – Bug 846848
mount -o loop allows mounting filesystems that are already mounted
Last modified: 2012-08-15 11:55:35 EDT
Description of problem:
mount -o loop allows users to mount a filesystem already mounted with no warning.
This seems dangerous. For example, when I run mount -o loop / it causes / to mount onto itself and immediate filesystem corruption.
Version-Release number of selected component (if applicable):
Tested on RedHat 5, 6 and Fedora 17.
Steps to Reproduce:
1. Mount a block device already mounted with the loop option:
mount -o loop <block device> <mount point>
A loopback device is created from the block device and mounted with no errors.
The command fails with a warning that the filesystem is already mounted.
The mount(8) command does not play such role in the system -- it's
kernel (filesystem driver) business to define what is allowed. The
behavior is filesystem specific -- for example ext4 allows to use MMP
(multi-mount-protection, since e2fsprogs 1.42) to avoid this kind of
Seems like not a bug. Sorry.