rsync - Jan 2013 - [Bug 9594] New: Error transferring user and non-user xattr using --fake-super under Linux

https://bugzilla.samba.org/show_bug.cgi?id=9594

           Summary: Error transferring user and non-user xattr using
                    --fake-super under Linux
           Product: rsync
           Version: 3.1.0
          Platform: All
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: core
        AssignedTo: wayned at samba.org
        ReportedBy: succinic.anhydride at yahoo.com
         QAContact: rsync-qa at samba.org


Overview:
I'm using rsync -aX as root on the sender (local) and --fake-super on the
receiver (remote) to preserve attributes. I'm using version 3.1.0dev as I
needed a solution to Bug 8201
(https://bugzilla.samba.org/show_bug.cgi?id=8201). I get the error "could
not
find xattr #1 for [foo]" when trying to transfer a file that has both a
non-user extended attribute with a long string value AND a user extended
attribute where the name of the user EA preceeds "user.rsync" in
lexical sort
order. The error is triggered only if the transfer is remote AND rsync is run
as root on the local/sender side so both non-user and user attrs are
transferred.

Steps to reproduce:
1. sudo touch foo
2. sudo setfattr -n user.rsx -v "1" foo ## user.rsx sorts before
user.rsync
3. sudo setfattr -n security.selinux -v
"system_u:object_r:cachefiles_var_t:s0"
foo ## non-user EA with a long string value
5. sudo rsync -i -aOzAX --numeric-ids --rsync-path="rsync
--fake-super" foo
user at remote:/tmp/ ## user does not have root access on host remote

Actual Results:
  <f+++++++++ foo
  [receiver] could not find xattr #1 for foo
  rsync error: protocol incompatibility (code 2) at xattrs.c(620)
[receiver=3.1.0dev]

Expected Results: no error, file and xattrs transferred successfully

System details:
Local/sender and remote/receiver are RHEL 6.3 with rsync 3.1.0dev

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https://bugzilla.samba.org/show_bug.cgi?id=9594

--- Comment #1 from Kuba Ober <kuba at mareimbrium.org> 2014-04-30
01:20:39 UTC ---
I can reproduce under 3.1.1pre1. The cause of the problem is as follows:

Note that the rsync_xa list items contain the xattr name and value *but also*
an attribute *index* (num!). 

1. The sender is sorting the rsync_xa list alphabetically on the xattr name in
rsync_xal_get. The attribute indices (num members) are set *after this sort*.

2. The receiver then proceeds to append RSYNC_PREFIX ("user.rsync.")
to the
xattr name in receive_xattr, and resorts the list. Now the attribute indices do
not match the list order.

3. The receiver then proceeds to iterate through this list in
recv_xattr_request with the assumption that the 
num indices are ascending within the list. The lexicographic sort performed in
step 2 above breaks this assumption.

Since I don't understand why the list needs to be lexicographically sorted
at
all, I don't know which of the two fixes below would be desirable: 

Fix 1: Don't sort the list in receive_xattr iff HAVE_LINUX_XATTR is defined.
Fix 2: Don't assume that the list indices are sorted in recv_xattr_request.
The
change would be from

while (cnt && rxa->num < num) {

to

while (cnt && rxa->num != num) {

Cheers, Kuba

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Wayne Davison <wayned at samba.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #2 from Wayne Davison <wayned at samba.org> 2014-05-26
21:09:25 UTC ---
Yeah, the bug seems to be that the receiver is aborting the scan for the
rxa->num item too soon when the sorting of the items caused the num values to
be scrambled. I am applying (essentially) your 2nd fix to the code.  Thanks for
diagnosing the issue!

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