Bug 421201 - SELinux prevents cups from saving printers.conf
SELinux prevents cups from saving printers.conf
Product: Fedora
Classification: Fedora
Component: selinux-policy (Show other bugs)
All Linux
low Severity high
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Assigned To: Daniel Walsh
Fedora Extras Quality Assurance
: Reopened
Depends On:
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Reported: 2007-12-12 05:52 EST by Andrew Kisliakov
Modified: 2008-05-07 14:11 EDT (History)
1 user (show)

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Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2008-05-07 14:11:42 EDT
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RHEL 7.3 requirements from Atomic Host:
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Description Andrew Kisliakov 2007-12-12 05:52:35 EST
Description of problem:

SELinux is preventing CUPS from saving its printer configuration file
/etc/cups/printers.conf. As a result, it is impossible to create new print
queues that will remain present after CUPS is restarted.

Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1. Set SELinux to 'enforcing'
2. # lpadmin -ptest -v lpd://
3. Restart cups

Actual results:

Queue 'test' is created but disappears after cups restarted.

Expected results:

Queue 'test remains after cups is restarted.

Additional info:

The following denial is reported by SELinux:
SELinux is preventing /usr/sbin/cupsd (cupsd_t) "rename" to (cupsd_etc_t)

According to the CUPS source scheduler/printers.c, the process of saving the
/etc/cups/printers.conf file attempts to create a temporary backup file
/etc/cups/printers.conf.0 using the rename() function. This operation is being
blocked by SELinux. The file /var/cups/error_log contains the following lines
which confirm this:

E ... Unable to backup printers.conf - Permission denied
E ... Unable to save printers.conf - Permission denied
E ... Unable to restore printers.conf - Permission denied
Comment 1 Daniel Walsh 2007-12-12 10:02:13 EST

# restorecon -R -v /etc/cups

Fix the problem?

This looks like a labeling problem. 

Do you have any avc messages in /var/log/audit/audit.log

When I executed this command on my box, it worked fine.
Comment 2 Andrew Kisliakov 2007-12-14 05:21:07 EST
Yes - that fixed the problem.

There are 3 avc messages each time the problem occurred:

Dec 13 17:17:16 kingsview kernel: audit(1197566236.631:25): avc:  denied  {
rename } for  pid=3585 comm="cupsd" name="printers.conf" dev=dm-0 ino=430399
tcontext=root:object_r:cupsd_etc_t:s0 tclass=file

Dec 13 17:17:16 kingsview kernel: audit(1197566236.631:26): avc:  denied  {
write } for  pid=3585 comm="cupsd" name="printers.conf" dev=dm-0 ino=430399
tcontext=root:object_r:cupsd_etc_t:s0 tclass=file

Dec 13 17:17:16 kingsview kernel: audit(1197566236.632:27): avc:  denied  {
rename } for  pid=3585 comm="cupsd" name="printers.conf.O" dev=dm-0 ino=425602
tcontext=system_u:object_r:cupsd_etc_t:s0 tclass=file

Comment 3 Daniel Walsh 2007-12-17 10:23:32 EST
Yes all of these indicate that the printers.conf file is labeled incorrectly.

I have no idea how this got labeled wrong.  If you are able to figure out the
way this file got mislabled, please reopen this bug.
Comment 4 Andrew Kisliakov 2007-12-17 10:47:22 EST
This happened to me on two systems, both running in VMWare virtual machines.

In one system, I had originally installed Fedora 6 and upgraded to 8. It's
possible that something unusual may have happened there earlier, which I won't
be able to remember or track down.

However, the other system was practically a fresh installation of Fedora 8, with
all the package updates that were current at the time the bug was reported. 

Additionally, it know that this had happened to another person, who, like me,
had upgraded his system from Fedora 6 to 8.
Comment 5 Daniel Walsh 2007-12-17 17:43:38 EST
Then that probably means some application outside of cups created the
printers.conf or some how cups got run without a transition.  

Tim is there something in the updates that recreates this file?
Comment 6 Tim Waugh 2007-12-18 08:44:34 EST
Andrew: by what means were these queues configured?  For example, did they
automatically appear when the printer was plugged in, or did you need use an
application to configure them?  If an application, which did you use (e.g. CUPS
web interface, System->Administration->Printing in GNOME [this is called
system-config-printer], the KDE configuration tool, ...)?

I can see that you are trying to add a queue using the lpadmin tool, but I need
to know which tool was used prior to that.

Also, would it be possible for you to attach the printers.conf file to this bug

There is another bug report that has similarities to this one: bug #245672.
Comment 7 Andrew Kisliakov 2007-12-19 05:31:34 EST
Dear Tim,

Thanks for the questions. Actually, there is currently no printer physically
attached, nor did any printers automatically appear, to my recollection. The
problem occurred shortly after installing Fedora 8, so the possibility of
interference by another tool is minimal.

I have re-partitioned my hard disk and am currently re-installing a clean Fedora
8. All the default installation options are being used. I will try to reproduce
the bug and let you know how I go. I will try to attach a relevant printers.conf
file as soon as I can.

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