[Dazuko-devel] Re: [Dazuko-help] Dazuko and Linux 2.6

[John Ogness]

Hi,

Yes, I have been keeping my eye on 2.5/2.6. I am about to release Dazuko 
version 2.0, which has been a major achievement for Dazuko (and a *lot* 
of work). Once it is available, I will be able to start focussing on 
Linux 2.6 (and FreeBSD 5).

In 2.4 (and earlier) there was no way that you could implement your own 
file access security module without major patches to the kernel. As a 
result, Dazuko hooks the system call, thus allowing it to have first say 
for file accesses (without requiring kernel patches). Although this 
works, it fits more into the category of "hacking the kernel" rather 
than "securing the kernel".

With 2.5/2.6, Linux provides an interface for implementing your own file 
access security module. This means that Dazuko will no longer need to 
hook the system calls. Although this makes Dazuko's job easier, it will 
require me (or someone) to appropriately match the Linux 2.6 security 
API to Dazuko. I have seen several examples of this and it looks like 
getting the access information to Dazuko will be the easy part.

However, I have not yet looked at the virtual file system, chroot 
models, and local name lookups for the new kernel. I am a lot more 
worried that these (more complex) pieces have changed considerably. (I 
am assuming they've changed because they changed quite a bit from 2.2 to 
2.4.)

I will most likely start working on the 2.6 port in December. If you 
subscribe the the dazuko-devel mailing list, we can start tackling this 
issue together.

John Ogness


Michael Grigoriev wrote:
> Hi,
>
> I've been considering using Dazuko to get file access/change notifications
> in my network filesystem [http://www.luminal.org/wiki/index.php/FunFS].
>
> Dazuko would allow me subscribe to notifications on an entire subtree in one
> go instead of having to subscribe to every file, like FAM. It would also let
> me block attempts to open files long enough for me to possibly get an oplock
> on it, thus delaying access further giving the filesystem time for force any
> client with outstanding write cache to flush it. In other words, it would be
> really useful.
>
> As I do most of my development on Linux 2.5/2.6, I started looking into
> porting Dazuko to it. But here's the problem: it appears that sys_call_table
> is no longer exported to the modules (starting with 2.5.41 I think).
>
> Here's some related information I was able to find on LKML:
> [http://lists.insecure.org/lists/linux-kernel/2003/May/0788.html]
>
>
> > It's unexported because there is no correct use for it and that it can't
> > be used correctly either. Tell me which lock your module uses to protect
> > modifications to it? Tell me how you handle other modules trying to
> > overload the same syscall and those modules loading before your module but
> > then unloading while yours is still loaded?
> >
> > It's the wrong mechanism to do ANYTHING. Really.
>
>
> So I was wondering if you've looked at 2.6 support at all, and if you had
> any ideas about how to do it.
>
> Thanks in advance.

--
Dazuko Maintainer