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Date: Thu, 8 Nov 2012 10:43:04 +0400
Message-ID: <CAA91j0UthFpt3TeJWUV4YAMyKdEKhYGZrK4j8odPd6td_s-g9w@mail.gmail.com>
Subject: Re: Effective process GID is ignored when client creates file on NFS
From: Andrey Borzenkov <arvidjaar@gmail.com>
To: "Myklebust, Trond" <Trond.Myklebust@netapp.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>,
        "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
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Sender: linux-nfs-owner@vger.kernel.org

On Thu, Nov 8, 2012 at 7:12 AM, Andrey Borzenkov <arvidjaar@gmail.com> wrote:
> В Wed, 7 Nov 2012 20:35:55 +0000
> "Myklebust, Trond" <Trond.Myklebust@netapp.com> пишет:
>
>> > -----Original Message-----
>> > From: linux-nfs-owner@vger.kernel.org [mailto:linux-nfs-
>> > owner@vger.kernel.org] On Behalf Of Andrey Borzenkov
>> > Sent: Wednesday, November 07, 2012 2:28 PM
>> > To: J. Bruce Fields
>> > Cc: linux-nfs@vger.kernel.org
>> > Subject: Re: Effective process GID is ignored when client creates
>> > file on NFS
>> >
>> > 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.
>>
>> So is it possible that you forgot to turn off root squashing on the
>> server before testing?
>>
>
> All filesystems are exported with anon=0 in this configuration. But if
> root suqashing is active, files should not appear as owned by UID 0,
> should not they?

OK this gave me idea. So the problem is indeed anon=0. If I reexport
the same filesystems with root=... option, files are created with
correct group ownership. I have to think about it, but on the first
glance NetApp behavior is correct. As root= option is missing it maps
root to anonymous user, and as anon=0 is present, this anonymous user
is root. What do standards say about group ownership in this case?