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Date: Wed, 7 Nov 2012 23:28:01 +0400
From: Andrey Borzenkov <arvidjaar@gmail.com>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: linux-nfs@vger.kernel.org
Subject: Re: Effective process GID is ignored when client creates file on
 NFS
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В Wed, 7 Nov 2012 14:13:36 -0500
"J. Bruce Fields" <bfields@fieldses.org> пишет:

> On Mon, Oct 29, 2012 at 06:09:29PM +0400, Andrey Borzenkov wrote:
> > I have met application that is badly broken when installed on NFS.
> > The reason is - it expects files to belong to specific group. It
> > switches to this group on startup (explicit setgid) and creates
> > files. But files come out as belonging to GID 0.
> > 
> > I finally reduced it to this trivial script:
> > 
> > === cut here ===
> > #include <sys/types.h>
> > #include <sys/stat.h>
> > #include <fcntl.h>
> > #include <unistd.h>
> > 
> > main()
> > {
> >         int fd;
> > 
> >         setgid(107);
> >         fd = open("bar", O_CREAT, 0666);
> >         close(fd);
> > }
> > === cut here ===
> > 
> > On local storage file comes with GID 107; on NFS file comes with
> > GID 0.
> > 
> > Linux is SLES10 SP3 with relatively old kernel:
> > 2.6.16.60-0.89.1-smp, server(s) are NetApp with different Data
> > ONTAP versions (7.x and 8.1.1 as the last).
> > 
> > Client passes correct credentials (UID:0, GID:107), but does not
> 
> Those are the credentials in the rpc header on the CREATE call?
> 

Yes.

> > explicitly request file ownership in CREATE call (uid set_it - 0,
> > gid set_it - 0).
> 
> The client shouldn't have to set the owner or group itself.
> 
> So this is server behavior.
> 
> Have you checked that the directory you're creating in doesn't have
> the sgid bit?

Yes. It does not.

>              Or perhaps there's some other server configuration that
> causes this.

It appears that server ignores passed group if UID == 0. It correctly
creates files if UID != 0. I got bug number from support but it is
non-public and no information is visible so far. I asked about
possible workaround (or undocumented options) but have not got any reply
as yet.