samba - Apr 2016 - truecrypt on synology as subfolder

Just a small question.

=============I was really just meaning to ask whether there are issues with
running
truecrypt inside a samba share.

My system had never had any issues but now I was writing to a folder 
that is a truecrypt mount inside a samba share and the smbd process 
writing into it blocked or is still "D" waiting for IO and I cannot
kill
it.

So the question was whether there are issues with running truecrypt 
inside a tree being served by smbd, but I now know that for a fact there 
are :p.

Still, if you have anything to say on it, please do so.

Copying a file to my mounted samba share did not work, the files are 
created by they remain at 0 size. Then apparently smbd blocks in IO and 
never continues, never recovers. I cannot kill the process, I will have 
to reboot the NAS but it won't unmount filesystems so I need a hard 
reset.

Regards

=============


On Synology DiskStation NASses there is typically only file-level 
encryption available via eCryptFS.

I had once seen the note that NFS onto an ecryptfs share wouldn't work.

Now SAMBA onto ecryptfs does work.

I just managed to get TrueCrypt compiled and reasonably working.

I mounted a container in a subdirectory of my home dire that I have 
mounted from a linux box.

But writes to this subdirectory fail over the samba mount.

The files are created but retain a size of zero.

All of a sudden a lot of stuff hangs on this computer. I cannot do ls /, 
or df, and I think I am going to try to dismount that share now.

Well this is fun, never had anything like this before:

malloc: unknown:0: assertion botched
free: called with unallocated block argument
last command: ls
Aborting...

Warning: Program '/bin/bash' crashed.


This was trying to tab-complete a directory in /

This is in my syslog. It was an hour and a half ago and I assume it was 
caused by, or related to, writing to that truecrypt mount.:

Apr 29 18:58:43 kubuntu kernel: [280345.596101] CIFS VFS: sends on sock 
ffff88012a605400 stuck for 15 seconds
Apr 29 18:58:43 kubuntu kernel: [280345.596124] CIFS VFS: Error -11 
sending data on socket to server
Apr 29 18:58:58 kubuntu kernel: [280360.612052] CIFS VFS: sends on sock 
ffff88012a605400 stuck for 15 seconds
Apr 29 18:58:58 kubuntu kernel: [280360.612067] CIFS VFS: Error -11 
sending data on socket to server
Apr 29 19:13:03 kubuntu kernel: [281205.857294] CIFS VFS: No writable 
handles for inode


After that:

Apr 29 19:27:03 kubuntu kernel: [282046.009506] CIFS VFS: No writable 
handles for inode
Apr 29 19:29:03 kubuntu kernel: [282166.033596] CIFS VFS: No writable 
handles for inode
Apr 29 19:41:03 kubuntu kernel: [282886.161769] CIFS VFS: No writable 
handles for inode
Apr 29 19:43:09 kubuntu kernel: [283012.170066] CIFS VFS: Server 
diskstation has not responded in 120 seconds. Reconnecting...
Apr 29 19:45:16 kubuntu kernel: [283138.298055] CIFS VFS: Server 
diskstation has not responded in 120 seconds. Reconnecting...
Apr 29 19:47:22 kubuntu kernel: [283264.414066] CIFS VFS: Server 
diskstation has not responded in 120 seconds. Reconnecting...

I restarted the samba on the server and now my "ls /" still has
trouble:

ls: cannot access '/nasdev': Host is down
ls: cannot access '/nashome': Host is down

There are a lot of smbd instances running on the server and they are all 
running under my user.

I cannot kill them and their ps flags are all D: uninterruptible sleep 
(usually IO)

I can unmount shares now but remounting fails:

mount error(112): Host is down

Stopping smbd on the server goes:

stop smbd ... no pid file, but process exist
stop winbindd ... not running
stop nmbd ... not running
smbd still running, wait 10 sec, force kill

Starting doesn't work anymore, it lists all the existing processes:

start nmbd ... ok
start smbd ...
smbd is running: 31035 30984 2817 2712 2609 2493 2396 2254 2150 2048 
1943 1841 1704 1605 1504 1404 1263 1163 1063 966 864 720 621 524

There are no file handles open on the temp directory at which the 
truecrypt is mounted:

# lsof mtest
<nothing>

But cannot umount

umount: can't umount /volume1/media/mtest: Device or resource busy

cannot remove the device mapper thing either of course:

# dmsetup remove truecrypt1
device-mapper: remove ioctl failed: Device or resource busy
Command failed

Basically there are probably still smbd processes preventing that dir 
form being umounted.

I do not have the error anymore that cp gave when I tried to cp 
something to the directory over smb.

But it said something with "fwrite".

I probably won't be able to reboot the NAS, I will have to hard reset 
it.

NOW I am finding it:

smbd      30984     xen   28uW     REG      253,0 47316992         13 
/volume1/media/mtest/.xaa.q80ZIO

xaa was a 48MB file I was trying to write to the container over smb.

trying to rm the file blocks the process (shell).

Now I cannot kill rm.

I think Synology has protected as against attaching a debugger so I also 
cannot (try to) close that way.

On Sat, Apr 30, 2016 at 12:26:35AM +0200, Xen wrote:
> Just a small question.
> 
> =============> I was really just meaning to ask whether there are issues
with
> running truecrypt inside a samba share.
> 
> My system had never had any issues but now I was writing to a folder
> that is a truecrypt mount inside a samba share and the smbd process
> writing into it blocked or is still "D" waiting for IO and I
cannot
> kill it.
> 
> So the question was whether there are issues with running truecrypt
> inside a tree being served by smbd, but I now know that for a fact
> there are :p.
> 
> Still, if you have anything to say on it, please do so.
> 
> Copying a file to my mounted samba share did not work, the files are
> created by they remain at 0 size. Then apparently smbd blocks in IO
> and never continues, never recovers. I cannot kill the process, I
> will have to reboot the NAS but it won't unmount filesystems so I
> need a hard reset.
That sounds like a kernel bug. Samba only uses normal open/pread/pwrite/
close calls which should work on top of truecrypt as far as I know.

Jeremy Allison schreef op 30-04-2016 1:06:
>> Copying a file to my mounted samba share did not work, the files are
>> created by they remain at 0 size. Then apparently smbd blocks in IO
>> and never continues, never recovers. I cannot kill the process, I
>> will have to reboot the NAS but it won't unmount filesystems so I
>> need a hard reset.
> 
> That sounds like a kernel bug. Samba only uses normal 
> open/pread/pwrite/
> close calls which should work on top of truecrypt as far as I know.


Before I had issues on some device using TrueCrypt because the entire 
thing would hang (mostly SMBD, then) when I read or actually wrote files 
to a truecrypt volume mounted inside of another filesystem, so that smbd 
would have to cross a filesystem boundary.

I never tested what would happen if the share itself was in the mounted 
crypt, from the beginning.

I now compiled LUKS on the device and I get an even stranger error in a 
certain sense.

 From the "top level" samba share, the subdirectory that has LUKS 
mounted, doesn't show any files.

However, when I create another share directly on the mounted LUKS 
subfolder, the files are there.

So the transition from regular filespace to LUKS filespaces (different 
volume) is not getting this LUKS filespace to appear empty to Samba, but 
not to the linux system itself. Is this to be expected?

Is that normal operation, this?

Regards.

ps. it is not a great problem because the intent is probably going to be 
to share an entire crypt container anyway, so the problem wouldn't 
surface, I just wonder whether it is normal.