Bug 62558 - chmod g=o clears setgid bit
chmod g=o clears setgid bit
Product: Red Hat Linux
Classification: Retired
Component: fileutils (Show other bugs)
All Linux
medium Severity low
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Assigned To: wdovlrrw
Aaron Brown
Depends On:
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Reported: 2002-04-02 11:35 EST by Alexander Dupuy
Modified: 2007-04-18 12:41 EDT (History)
0 users

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Doc Type: Bug Fix
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Last Closed: 2002-04-04 10:12:42 EST
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Description Alexander Dupuy 2002-04-02 11:35:29 EST
From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:0.9.9) Gecko/20020311

Description of problem:
chmod = operator uses all four bits from {u,g,o} when modifying permissions,
whereas it should probably operate only on the rwx bits, and not the
setuid/setgid/sticky bits, since these don't have commensurable meanings
(certainly not for sticky, and arguably for setuid/setgid).

Version-Release number of selected component (if applicable):
chmod (GNU fileutils) 4.0.36

How reproducible:

Steps to Reproduce:
1. mkdir /tmp/foo.d
2. chmod 2775 /tmp/foo.d
3. chmod g=o /tmp/foo.d
4. ls -ld /tmp/foo.d

Actual Results:  drwxr-xr-x    2 dupuy    sysman       1024 Apr  2 11:14 /tmp/foo.d

Expected Results:  drwxr-sr-x    2 dupuy    sysman       1024 Apr  2 11:14

Additional info:

Not sure what, if anything, POSIX.2 specifies about the behavior of chmod g=o. 
If they require this pretty stupid and unexpected behavior, I guess you have to
implement it as such.  It's quite possible they have nothing to say on the
subject, though, since g=o type operations may be an extension of the POSIX.2 spec.
Comment 1 Alan Cox 2002-04-04 10:12:37 EST
Single Unix states 

If the calling process does not have appropriate privileges, and if the group ID
of the file does not match the effective group ID or one of the supplementary
group IDs and if the file is a regular file, bit S_ISGID (set-group-ID on
execution) in the file's mode will be cleared upon successful return from chmod(). 

Additional implementation-dependent restrictions may cause the S_ISUID and
S_ISGID bits in mode to be ignored. 

Comment 2 Bernhard Rosenkraenzer 2002-04-04 10:32:18 EST
This is fixed in fileutils 4.1 (RH 7.2 and later)

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