Bug 846848

Summary:	mount -o loop allows mounting filesystems that are already mounted
Product:	Red Hat Enterprise Linux 6	Reporter:	Eric Parish <eric.parish>
Component:	util-linux-ng	Assignee:	Karel Zak <kzak>
Status:	CLOSED NOTABUG	QA Contact:	qe-baseos-daemons
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	6.2
Target Milestone:	rc
Target Release:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2012-08-15 15:55:35 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Eric Parish 2012-08-08 21:30:32 UTC

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.  

How reproducible:
Always

Steps to Reproduce:
1. Mount a block device already mounted with the loop option:
mount -o loop <block device> <mount point>
  
Actual results:
A loopback device is created from the block device and mounted with no errors. 

Expected results:
The command fails with a warning that the filesystem is already mounted. 

Additional info:

Comment 2 Karel Zak 2012-08-15 15:55:35 UTC

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
problems.

Seems like not a bug. Sorry.