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Old 08-04-2011, 04:08 PM   #1
Reuti
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Registered: Dec 2004
Location: Marburg, Germany
Distribution: openSUSE 11.4
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Does NFSv4 serve only files which are at least readable? (was: NFSv4 and SUID mount)


Hi,

I was used to mount with NFSv3 on clients in a private part of a cluster one mount point with honoring the suid bit of files on the NFSv3 server by specifying it as option in /etc/fstab. This is no longer in NFSv4 and I get "Permission denied" for such files when I try to execute them on the client. When I mount on the client the same mount point by specifying nfsvers=3 itís working again (without changing anything on the server).

Is this a feature of NFSv4, or does it need a special setup?

As I couldnít find anything related to this in any logfile, the only hint I got was when mounting in verbose mount that the specified option is just ignored.

Last edited by Reuti; 08-06-2011 at 08:29 AM. Reason: Changed title to reflect results so far
 
Old 08-05-2011, 04:13 PM   #2
Reuti
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Registered: Dec 2004
Location: Marburg, Germany
Distribution: openSUSE 11.4
Posts: 1,319

Original Poster
Rep: Reputation: 252Reputation: 252Reputation: 252
Does NFSv4 serve only files which are at least readable?

While playing around with the issue of the remote execution of a suid file, it turned out that the set permissions:
Code:
-r-s--x--x 1 root root 51K Jan 13  2010 rsh
avoid the file to be served at all to the client. Changing the permissions to:
Code:
-r-sr-xr-x 1 root root 51K Jan 13  2010 rsh
gave the expected behavior again.

So it boils down to the question why in NFSv3 itís possible to have access to --x files, while in NFSv4 it must be r-x for group/other?

NB: For the ones wondering about the purpose of a suid rsh: itís from the GridEngine queuing system to allow a tight integration of slaves tasks in former times as it was replaced by a built-in method. Nevertheless some touchy applications need the older startup of their slave tasks.
 
  


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