helpGNU Core Utilities - Support: sr #107704, cp: fchown called before fchmod,...

 
 

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sr #107704: cp: fchown called before fchmod, unable to set file mode

Submitter:  Milan Novak <milan123>
Submitted:  Fri 27 May 2011 01:29:13 PM UTC
 
Category:  None Priority:  5 - Normal
Severity:  4 - Important Status:  None
Privacy:  Public Assigned to:  None
Open/Closed:  Open Operating System:  None

Fri 27 May 2011 01:29:13 PM UTC, original submission:  

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@mtest:/home/hp/coreutils $ id
uid=1058(hp) gid=20(users) groups=65535(last)
hp@mtest:/home/hp/coreutils $ ll source target
target not found
-rwxrwxrwx   1 elzu       radia           32 May 20 15:50 source
hp@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@mtest:/home/hp/coreutils $ rm -f target

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

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

hp@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)

Milan Novak <milan123>

 

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