[Unionfs] unionfs-2.5_for_2.6.27-rc6 and Kernels 2.6.27 to 2.6.27.4

[Erez Zadok]

In message <49126C3A.7010308 at itamservices.de>, Daniel Reichelt writes:
> Hi list,
> 
> I have an unionfs mount setup like this:
> 
> # mkdir br1 br2 rwunion
> # mount -t nfs -o ro server:/nfsexport /br2
> # mount -t unionfs -o dirs=/br1=rw:/br2=ro none /rwunion/
> 
> So far so good. When I try to add new files or remove files that pre-existed on
> the ro-nfs branch, that works just fine. However appending/chaning files
> originating from the ro-nfs branch, I get this:
> 
> # ls -la /br1
> # ls -la /br2
> -rw-r--r-- 1 root root   55 2008-11-06 04:41 test
> 
> # ls -la /rwunion
> -rw-r--r-- 1 root root   55 2008-11-06 04:41 test
> 
> # echo >test
> bash: test: Permission denied

Daniel and Michael,

I've tried to reproduce this on my end and so far no luck.  I tried
unionfs-2.5 for 2.6.27-rc, plus the TOMOYO-related patch which you had, plus
the EXPORT_SYMBOL(security_inode_permission) patch.  I tried it w/ two
branches where the r/o branch was either nfsv3 or ext3, and was physically
mounted readonly (plus the branch was marked ro).  I tried to trigger
copyups as either root or a non-root user.  So far I'm not able to reproduce
the scenario in which a root user is getting the EACCES you're seeing above.

So my environment is probably different than yours somehow.  I need more
info:

- kernel .config you're using
- vanilla kernel or patched: which patches?  can I have them?
- cat /proc/mounts for me
- are you using pivot_root, bind mounts, chroot, etc.?
- are you using selinux/lsm/tomoyo or the like?

Is there anything else you can do to help me reproduce this?  Perhaps give
me a virtual machine image or live-cd w/ your stuff?  Or temp access to your
system?

BTW, feel free to open a bugzilla report on this at
https://bugzilla.filesystems.org/.

Thanks,
Erez.