[Bug 12806] New: Deleting in a row of hardlinked snapshots resets file permissions.

[samba-bugs at samba.org]

https://bugzilla.samba.org/show_bug.cgi?id=12806

            Bug ID: 12806
           Summary: Deleting in a row of hardlinked snapshots resets file
                    permissions.
           Product: rsync
           Version: 3.1.0
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P5
         Component: core
          Assignee: wayned at samba.org
          Reporter: hww at delember-wyes.de
        QA Contact: rsync-qa at samba.org

Created attachment 13239
  --> https://bugzilla.samba.org/attachment.cgi?id=13239&action=edit
Log file of bug reproduction

Overview:
In an differential backup system with hard-linked copies of unchanged files,
deleting one snapshot resets the permission bit on all files.

Steps to reproduce:
1) Set up a source directory, fill in a couple of files. Some text is just
fine.
Make one of these files have 444 permissions.

2) Set up a different directory to hold snapshots of the source directory.

3) Make a unique name for a snapshot, using e.g. the current date/time.

4) Make a snapshot using rsync:
rsync -ar --itemize-changes src/ snapshots/`echo $snap`/
$snap contains the name of the snapshot. Save this name in a file
"lastsnapshot".

5) Make a new name for a new snapshot and make it using:
rsync -ar --itemize-changes --link-dest=`pwd`/snapshots/`cat lastsnapshot`/
src/ snapshots/`echo $snap`/. Again, save the name of the last snapshot.

6) Repeat step 5) a couple of times. In the snapshot directory, you will get a
row of snapshots. All files in each snapshot is hard-linked to the counterparts
in the other snapshots. Watch the permission bits of the one file with 444
permissions: Everything is ok.

7) Now, deliberately delete one of the snapshots using e.g.
rsync -r --delete `mktemp -d`/ snapshots/2017-05-26-15-00-53/

8) Now all of the files in all snapshots have 644 permissions. This will cause
the re-transmission of that file with the following snapshot.

Actual results: On deletion of a snapshot, hardlinked files get the wrong
permissions.

Expected results: Permission bits should be left intact.

Attached is a log file where I documented this behaviour.

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