GNU bug report logs - #8752
cp: fchown called before fchmod, unable to set file mode

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Bob Proulx <bob <at> proulx.com>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#8752: closed (cp: fchown called before fchmod, unable to set
 file mode)
Date: Wed, 01 Jun 2011 19:18:02 +0000

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Your message dated Wed, 1 Jun 2011 13:17:28 -0600
with message-id <20110601191728.GA19127 <at> hysteria.proulx.com>
and subject line Re: bug#8752: cp: fchown called before fchmod, unable to set file mode
has caused the GNU bug report #8752,
regarding cp: fchown called before fchmod, unable to set file mode
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


-- 
8752: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=8752
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Contact help-debbugs <at> gnu.org with problems

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From: Milan Novak <milan.novak <at> gmail.com>
To: bug-coreutils <at> gnu.org
Subject: cp: fchown called before fchmod, unable to set file mode
Date: Sat, 28 May 2011 15:10:21 +0200

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Hello,

I believe that cp uses wrong order of syscalls when applying target file
attributes; fchown(2) is called before fchmod(2).
As a result it looses access to target file and is unable to apply file mode
correctly; error message is as follows
"cp: preserving permissions for `target': Not owner"

The problem arises when -p (preserve attributes) is present and file owner
is different from user doing the copy.

Same operation using cp on hp-ux 11.31 is successfull, since hp-ux cp calls
chmod(2) before chown(2).

Please let me know what do you think about changing order of fchown(2) <=>
fchmod(2).

Kind Regards,
Milan

---

hp <at> mtest:/home/hp/coreutils $ id
uid=1058(hp) gid=20(users) groups=65535(last)
hp <at> mtest:/home/hp/coreutils $ ll source target
target not found
-rwxrwxrwx 1 elzu radia 32 May 20 15:50 source
hp <at> mtest:/home/hp/coreutils $ tusc -o tusc_hpuxcp.out /usr/bin/cp -p source
target; echo $? ; ll source target
0
-rwxrwxrwx 1 elzu radia 32 May 20 15:50 source
-rwxrwxrwx 1 elzu radia 32 May 20 15:50 target
hp <at> mtest:/home/hp/coreutils $ rm -f target

hp <at> mtest:/home/hp/coreutils $ tusc -o tusc_gnucp.out coreutils-8.11/src/cp
-p source target; echo $? ; ll source target
coreutils-8.11/src/cp: preserving permissions for `target': Not owner #>>>>
ERROR
1
-rwxrwxrwx 1 elzu radia 32 May 20 15:50 source
-rwx------ 1 elzu radia 32 May 20 15:50 target #>>> already owned by user
elzu, so chmod executed as user hp fails

hp <at> mtest:/home/hp/coreutils $ coreutils-8.11/src/cp --version | head -1
cp (GNU coreutils) 8.11

hp <at> mtest:/home/hp/coreutils $ uname -a
HP-UX mtest B.11.31 U ia64 2263078376 unlimited-user license

hp <at> mtest:/home/hp/coreutils $ egrep "target|chown|chmod|exit" tusc_*
tusc_hpuxcp.out:stat64("target", 0x7fffeec0)
............................................ ERR#2 ENT
tusc_hpuxcp.out:stat64("target", 0x40021110)
............................................ ERR#2 ENT
tusc_hpuxcp.out:stat64("target", 0x40021110)
............................................ ERR#2 ENT
tusc_hpuxcp.out:access("target", F_OK)
.................................................. ERR#2 ENT
tusc_hpuxcp.out:open("target", O_WRONLY|O_CREAT|O_TRUNC|0x800, 0)
....................... = 6
tusc_hpuxcp.out:utime("target", 0x7fffe5f0)
............................................. = 0
tusc_hpuxcp.out:chmod("target", 0100777)
................................................ = 0
tusc_hpuxcp.out:chown("target", 1021, 1005)
............................................. = 0
tusc_hpuxcp.out:chmod("target", 0100777)
................................................ ERR#1 EPM
tusc_hpuxcp.out:exit(0)
................................................................. WIFE)

tusc_gnucp.out:stat64("target", 0x7fffedf0)
............................................ ERR#2T
tusc_gnucp.out:stat64("target", 0x7fffeac0)
............................................ ERR#2T
tusc_gnucp.out:open("target", O_WRONLY|O_CREAT|O_EXCL|0x800, 0700)
..................... = 5
tusc_gnucp.out:utime("target", 0x7fffe7a8)
............................................. = 0
tusc_gnucp.out:fchown(5, 1021, 1005)
................................................... = 0     #>>> the problem
is HERE, CHOWN goes before CHMOD;
tusc_gnucp.out:fchmod(5, 0100777)
...................................................... ERR#1M     #>>> this
fails, since user hp is not the owner of the file anymore
tusc_gnucp.out:exit(1)
................................................................. WIFEX)

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From: Bob Proulx <bob <at> proulx.com>
To: Milan Novak <milan.novak <at> gmail.com>, 8752-done <at> debbugs.gnu.org
Subject: Re: bug#8752: cp: fchown called before fchmod, unable to set file mode
Date: Wed, 1 Jun 2011 13:17:28 -0600

Paul Eggert wrote:
> Paul Eggert wrote:
> > # echo "-n CHOWN" >>/etc/privgrp
> > # setprivgrp -f /etc/privgroup
> 
> Whoops, obviously I misspelled one of those two file names.
> I think the second one is right.  But you should read the
> manuals and check before trying it (I haven't used HP-UX
> in years).

The first was the misspelling, the second was the correct name.

Just to be clear, this next command will set it interactively.  You
can test the behavior without having made any permanent changes.  But
if you reboot the change will be gone.

  # setprivgrp -n CHOWN

Setting this file /etc/privgroup with the following contents will make
it persistent at boot time:

  -n CHOWN

See 'man 1m setprivgrp' for the HP-UX documentation.

And since I think this completely resolves the issue I am going to
close the ticket on it.  Please feel free to add additional comments.
If needed the ticket can be reopened at any time.

Bob

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