Bug 487582

Summary:	Root chown of file does not preserve setuid bit
Product:	Red Hat Enterprise Linux 5	Reporter:	Victor Gregorio <contactvictorg>
Component:	coreutils	Assignee:	Ondrej Vasik <ovasik>
Status:	CLOSED NOTABUG	QA Contact:	BaseOS QE <qe-baseos-auto>
Severity:	medium	Docs Contact:
Priority:	low
Version:	5.2	CC:	tim.w.connors
Target Milestone:	rc
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
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Clone Of:		Environment:
Last Closed:	2009-03-03 14:26:39 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 Victor Gregorio 2009-02-26 20:15:57 UTC

Description of problem:

On RHEL5, chown 0 <file> does not preserve the setuid bit of <file>.  This behavior is different than RHEL4, which preserves the setuid.  Is this change in /bin/chown's behavior intentional?

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

CentOS release 5.2 (Final)
coreutils-5.97-14.el5

How reproducible:

Always

Steps to Reproduce:

[root@flatline ~]# touch test
[root@flatline ~]# chmod u+s test
[root@flatline ~]# ls -l test
-rwSr--r-- 1 root root 0 Feb 26 04:11 test

[root@flatline ~]# chown 0 test
[root@flatline ~]# ls -l test
-rw-r--r-- 1 root root 0 Feb 26 04:11 test

Expected results:

The setuid bit is preserved when running the above steps on RHEL4

Additional info:

http://lkml.indiana.edu/hypermail/linux/kernel/9706.0/0068.html

Comment 1 Ondrej Vasik 2009-03-03 14:26:39 UTC

Thanks for report, I agree it is somewhat tricky behaviour but as said in 

upstream NEWS 5.3.0 (between RHEL-4 and RHEL-5):
"Do not optimize away the chown() system call when the file's owner
and group already have the desired value.  This optimization was
incorrect, as it failed to update the last-changed time and reset
special permission bits, as POSIX requires."

Posix formulation (http://www.opengroup.org/onlinepubs/000095399/utilities/chown.html):
"Unless chown is invoked by a process with appropriate privileges, the set-user-ID and set-group-ID bits of a regular file shall be cleared upon successful completion; the set-user-ID and set-group-ID bits of other file types may be cleared."

As no change is succesful completition it looks like POSIX requires it. Therefore I would call it NOTABUG and intentional change as we should be as POSIX compliant as possible. Closing NOTABUG.

Comment 2 Tim Connors 2010-07-27 01:07:43 UTC

You missed the first part of that clause though, Ondrej:

"Unless chown is invoked by a process with appropriate privileges"

I believe root has appropriate privileges.  I suspect that clause is not in support of the change made in the 2.6 kernel.  There may be other clauses, but not this one.

I believe this is still a bug.