Bug 174111

Summary:	mount allows loopback devices to be mounted more than once to the same mount point
Product:	[Fedora] Fedora	Reporter:	Radek Bíba <rbiba>
Component:	util-linux	Assignee:	Karel Zak <kzak>
Status:	CLOSED RAWHIDE	QA Contact:	Ben Levenson <benl>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	3
Target Milestone:	---
Target Release:	---
Hardware:	i386
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2006-01-03 18:10:27 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Radek Bíba 2005-11-24 18:00:44 UTC

From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20050922 Fedora/1.0.7-1.1.fc3 Firefox/1.0.7

Description of problem:
SSIA. Additional problem is that if a user has privilege to mount a loopback
device (also an encrypted partition) and accidentally mounts it once more he
can't unmount it, umount says it's mounted multiple times, and only root can
resolve it.

Version-Release number of selected component (if applicable):
util-linux-2.12a-24.5

How reproducible:
Always

Steps to Reproduce:
Scenario for root:
1. dd if=/dev/zero of=/tmp/testloop ibs=1024 count=1024; mkdir /tmp/testmnt;
mke2fs -F /tmp/testloop
2. mount -o loop /tmp/testloop /tmp/testmnt
3. mount -o loop /tmp/testloop /tmp/testmnt
(yeah, twice)

Scenario for a common user:
1. = the first step, as above
2. echo /tmp/testloop /tmp/testmnt ext2 loop,user 0 0 >> /etc/fstab
3. (as a common user)  mount /tmp/testmnt ; mount /tmp/testmnt
4. (as a the same common user) umount /tmp/testmnt

Actual Results:  
[1] no error, mounted twice (see `mount`)
[2] = [1] + the user cannot unmount it

Expected Results:  
[1] error message, mounted only once
[2] = [1] (thus mounted once) + unmountable by user

Additional info:

Comment 1 Karel Zak 2006-01-03 11:23:47 UTC

Good catch! The check for "alredy mounted" is based on EBUSY (mount(2)), but
this is not true for "-o loop" where the mount command creates always new device :-)

$ cat /etc/mtab | grep loop
/tmp/testloop /tmp/testmnt ext2
rw,noexec,nosuid,nodev,loop=/dev/loop0,user=zakkr 0 0
/tmp/testloop /tmp/testmnt ext2
rw,noexec,nosuid,nodev,loop=/dev/loop1,user=zakkr 0 0

$ cat /proc/mounts | grep loop
/dev/loop0 /tmp/testmnt ext2 rw,nosuid,nodev,noexec,nogrpid 0 0
/dev/loop1 /tmp/testmnt ext2 rw,nosuid,nodev,noexec,nogrpid 0 0

Comment 2 Karel Zak 2006-01-03 18:10:27 UTC

Fixed in FC4 and FC5. I'm going to fix it in FC3 with something more important...

Comment 3 Radek Bíba 2006-01-04 08:29:15 UTC

Thanks very much. I tried the new version on rawhide and it indeed works as
expected.