Topic: Client kernel update has broken SMB file access

[abovett]

Hi

I'm running several different versions of Linux and Windows on clients
connected to an SME Server 6.0.1 box. I recently started having
problems where some of the clients can't overwrite files on the server
(ibay shares mounted via smbmount). I have tracked the problem down to
be associated with recent kernel updates on the clients. I haven't
got all the relevant version numbers I'm afraid, but I can give some
of them (see list below).

To give an example ("mnt/SOL/copying" is a mount point for ibay
"copying" on SME server "SOL"):

[andrew@europa-fc3 ~]$ touch test.txt
[andrew@europa-fc3 ~]$ cp test.txt mnt/SOL/copying
[andrew@europa-fc3 ~]$ cp test.txt mnt/SOL/copying
cp: cannot create regular file mnt/SOL/copying/test.txt': Input/output error
[andrew@europa-fc3 ~]$

Note - the first copy - to a non-existant file - succeeds. The second
fails (after pausing for several seconds).

Clients with problems:
 Fedora Core 3, kernel 2.6.9-1.681_FC3
 SuSE Linux 9.1, kernel 2.6.5-7.111.5-default
 Ubuntu, kernel 2.6.8.1-3-386

Clients without problems:
 Fedora Core 3, kernel 2.6.9-1.678_FC3
 Mandrake 10.1, kernel 2.6.8.1-12mdk
 Vector Linux, kernel 2.6.7-ide4
 
In the case of the SuSE system, I noted that the problem started
immediately after the last kernel update, and that the info with the
kernel update said that it addressed vulnerabilities in the SMB file
system.

Anyone else getting this problem? Any ideas how to track it down? Not
sure it's exactly an SME server problem, but I think it may affect
other SME server users. I'm willing to run tests or dump logs (even
re-install OSs) if it will help solve this one - it renders half the
systems virtually useless at the moment!

Thanks

Andy B

[abovett]

I've now confirmed that this is a kernel bug - Fedora and SuSE mention it in their changelogs. Fedora have just fixed it with the latest kernel update. SuSE have not yet fixed it but there is a workaround - if shares are mounted using mount -t cifs instead of smbmount (equivalent to mount -t smbfs) then it works. Not sure of the difference but I'm guessing that cifs is smb direct over TCP/IP rather than using NetBIOS - can anyone confirm?

One disadvantage - I always make smbmount and smbumount setuid root so I can mount shares from userspace, but there's no direct equivalent for cifs. Still, I can live with that until a fix is released.

Andy B

[go_jesse]

cifs uses the new (NT and newer only) TCP port 445 to do network file transfers.

smbfs uses port 137,138,139  TCP and UDP and is compatible with Windows 9X

AFAIK

[abovett]

cifs uses the new (NT and newer only) TCP port 445 to do network file transfers.

smbfs uses port 137,138,139  TCP and UDP and is compatible with Windows 9X

AFAIK

Yes - that's how I understand it to work. The CIFS (port 445) version of the SMB protocol runs directly over TCP/IP and doesn't require NetBIOS.

Thanks for confirming this. I'm glad to have got to the bottom of the problem - it was getting to be a real hassle not being able to access my server properly from some of the Linux clients.

Andy B