Shared folder file permissions - changed in 3.0.4?

[FrozenCow]

I also ran into weird trouble with shared folders. Though I'm not sure whether it is related to this problem.
Setup: Archlinux guest on a Ubuntu host.
I noticed it happening when Sabnzbd moved its downloaded files to its 'completed' folder. When it did this, the files were not readable anymore. When doing 'ls -l' it showed ??? for the owner and ??? for the permissions fields. Here is where it gets even stranger: when remounting vboxsf, the permissions are correct again.
vboxsf is mounted using the following fstab line:
vboxshare /media/vboxshare vboxsf rw,dmode=777,fmode=777 0 0

I tried to mimic this behaviour and found a bug in the handling of vboxsf's permissions:

Code: Select all

[root@v070 test]# echo test > testfile
[root@v070 test]# ls -l
total 4
-rwxrwxrwx 1 root root 5 Apr 20 21:22 testfile
[root@v070 test]# chmod 000 testfile
[root@v070 test]# echo test > testfile
bash: testfile: Operation not permitted
[root@v070 test]# ls -l
total 4
-rwxrwxrwx 1 root root 5 Apr 20 21:22 testfile

So, for some reason vboxsf does something with permission-changes, but it doesn't show that. It does this even though they are set in the mount options (like I have). I have not yet been able to mimic the behaviour that Sabnzbd caused, but I think it is related.