Linux hfsplus corrupts chflags bits?

Linux hfsplus corrupts chflags bits?

[Paolo Giarrusso]

[Please CC me on replies as I'm not subscribed.]

The Linux hfsplus implementation seems to repeatedly corrupt
hfsplus_perm->rootflags; when the same filesystem is read on Mac OS X,
this changes the attribs touched by chflags and makes a random
selection of files "locked" and thus untouchable. This happened for me
on Ubuntu 12.04 "Precise Pangolin", based on a 3.2.0 kernel, reports
appear from various other versions and the source doesn't seem heavily
changed.

I've had experience of this, shared by other users on this
superuser.com discussion:
http://superuser.com/a/457494/46794

Given that hfsplus isn't even mentioned in MAINTAINERS, I've used
./scripts/get_maintainer.pl to select recipients.

To convince you that the flags are in fact set randomly, here's a
listing of the backup of my home created through rsync on Linux (which
supposedly isn't even aware of these flags). Notice: none of these
flags are supposed to be set.

# 'ls' -ld -O /Volumes/HFS+Backup/Users/pgiarrusso/*
drwx------   31 pgiarrusso  staff  uchg,nodump,opaque         1054 Aug
13 02:00 /Volumes/HFS+Backup/Users/pgiarrusso/Desktop
drwx------   36 pgiarrusso  staff  nodump                     1224 Jul
22 16:04 /Volumes/HFS+Backup/Users/pgiarrusso/Documents
drwx------  108 pgiarrusso  staff  uappnd                     3672 Aug
13 11:43 /Volumes/HFS+Backup/Users/pgiarrusso/Downloads
drwx------   13 pgiarrusso  staff  uappnd,uchg,opaque          442 Jul
22 05:04 /Volumes/HFS+Backup/Users/pgiarrusso/Dropbox
drwx------   53 pgiarrusso  staff  -                          1802 Aug
12 00:58 /Volumes/HFS+Backup/Users/pgiarrusso/Library
drwx------   11 pgiarrusso  staff  uchg,nodump,opaque          374 Jul
22 17:25 /Volumes/HFS+Backup/Users/pgiarrusso/Movies
drwx------   13 pgiarrusso  staff  uappnd,uchg,nodump          442 Jun
10 12:05 /Volumes/HFS+Backup/Users/pgiarrusso/Music
drwx------   15 pgiarrusso  staff  uappnd,nodump,opaque        510 Jun
10 12:05 /Volumes/HFS+Backup/Users/pgiarrusso/Pictures
drwxr-x---   11 pgiarrusso  staff  opaque                      374 Jul
 6 15:33 /Volumes/HFS+Backup/Users/pgiarrusso/Public
drwxr-xr-x   34 pgiarrusso  staff  uappnd,uchg,opaque         1156 May
27 12:39 /Volumes/HFS+Backup/Users/pgiarrusso/Sites
drwxr-xr-x    2 pgiarrusso  staff  uappnd,nodump,opaque         68 Jun
10 21:43 /Volumes/HFS+Backup/Users/pgiarrusso/VirtualBox VMs
-rwxr-xr-x    1 pgiarrusso  staff  uappnd,nodump,opaque       1703 Feb
19  2012 /Volumes/HFS+Backup/Users/pgiarrusso/bash-prompt.sh
drwxr-xr-x   22 pgiarrusso  staff  -                           748 Aug
10 19:47 /Volumes/HFS+Backup/Users/pgiarrusso/bin
lrwxrwxrwx    1 pgiarrusso  staff  nodump,opaque                37 Sep
27  2011 /Volumes/HFS+Backup/Users/pgiarrusso/default.sfx ->
/Users/pgiarrusso/opt/rar/default.sfx
-rw-r--r--    1 pgiarrusso  staff  uappnd,uchg          1375563169 Aug
 2 18:52 /Volumes/HFS+Backup/Users/pgiarrusso/heapdump-1343925310626.hprof
drwxr-xr-x   22 pgiarrusso  staff  uappnd,nodump               748 Aug
 1 22:15 /Volumes/HFS+Backup/Users/pgiarrusso/opt
drwxr-xr-x    7 pgiarrusso  staff  uappnd                      238 Apr
19 20:00 /Volumes/HFS+Backup/Users/pgiarrusso/share
drwxr-xr-x   35 pgiarrusso  staff  nodump,opaque              1190 Aug
10 00:06 /Volumes/HFS+Backup/Users/pgiarrusso/tmp

Cheers,
-- 
Paolo 'Blaisorblade' Giarrusso - Ph.D. Student
http://www.informatik.uni-marburg.de/~pgiarrusso/

Re: Linux hfsplus corrupts chflags bits?

[Matthew Garrett]

There was a similar problem with the userflags field - we were writing 
random data. It wouldn't surprise me if this is another case where a 
field is just not being initiaised.

-- 
Matthew Garrett | mjg59@srcf.ucam.org

Fwd: Linux hfsplus corrupts chflags bits?

[Paolo Giarrusso]

[Re-sending to LKML - it was rejected because my phone sent the mail
also in HTML.]

On Thu, Sep 13, 2012 at 11:35 PM, Matthew Garrett <mjg59@srcf.ucam.org> wrote:
> There was a similar problem with the userflags field - we were writing
> random data.
Ouch, sorry for the noise! I'm pretty sure it's exactly the same
problem: I wrote rootflags but meant userflags.
I might be wrong, but I think that's the case because your bugfix was
merged after 3.3. Instead I was running 3.2.

Somewhat unrelatedly, I noticed that most flags can't be set even by
ioctl, so Linux backup utilities can't preserve those flags.
Is that something which could be fixed, say by exposing them as
extended attributes?

I'll doublecheck that all randomly set flags are indeed userflags. To
be sure: userflags contains flags which can be set by the owner, while
rootflags can only be altered by the superuser, right? So I can check
here on Darwin's man chflags
(https://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/10.6/man1/chflags.1.html)

Cheers,
--
Paolo 'Blaisorblade' Giarrusso - Ph.D. Student
http://www.informatik.uni-marburg.de/~pgiarrusso/