From: Zwane Mwaikambo <zwane@linuxpower.ca>

smbfs tends to oops over a null server->ops->getattr in smb_proc_getattr().

Urban says:

 In 2.5 the server->ops is initialized when smbfs gets a connection, to
 match whatever the server is capable of or not. This happens after the
 mount syscall so smbfs is then mounted but not usable.

 Not sure if smb_lookup is always called before any other operation that
 uses server->ops. If it is then it would be enough to have a test there.

 Otherwise I will just change all users of server->ops to verify the
 pointer first and return -EIO or something.

Al Viro says (paraphrasing)

 ugh, we need mount2().

It doesn't look to me like we'll be getting mount2() in the 2.6 timeframe.
Zwane's patch implement's Urban's workaround.