NFSv3 / VFS and group problems

NFSv3 / VFS and group problems

[Philip Lawatsch]

Hi,

I've had the joy to debug a production system with a really crappy setup.

They have a user "fred" which belongs to ~5000 groups (say 
group1-group5000).


So far so bad. Even worse, they have a nfs backend  with lots of files 
which are owned by users belonging to these groups.

Ok, now my problem is that "fred" can open a file which is

-rw-rw----  someone group300 foo

but a read on this file will fail with EIO

Since group300 is way beyond the 16 groups nfs supports shouldn't fred 
actually get a EACCES back from the open call?

Problem happens with 2.6.13 (vanilla, not tainted) on both server and 
client.


kind regards Philip

Re: NFSv3 / VFS and group problems

[Philip Lawatsch]

Philip Lawatsch wrote:
> Hi,
> 
> I've had the joy to debug a production system with a really crappy setup.
> 
> They have a user "fred" which belongs to ~5000 groups (say 
> group1-group5000).
> 
> 
> So far so bad. Even worse, they have a nfs backend  with lots of files 
> which are owned by users belonging to these groups.
> 
> Ok, now my problem is that "fred" can open a file which is
> 
> -rw-rw----  someone group300 foo
> 
> but a read on this file will fail with EIO
> 
> Since group300 is way beyond the 16 groups nfs supports shouldn't fred 
> actually get a EACCES back from the open call?
> 
> Problem happens with 2.6.13 (vanilla, not tainted) on both server and 
> client.

Just tried it between two 2.6.15.1 machines. It works as expected there. 
Seems that the client actually screwed around with the machines more 
than he was willing to admit. Sorry for the noise.

kind regards Philip