linux-kernel - Re: [PATCH] NFS: fix client permission error after adding user to permissible group

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Message-ID: <CAPza5qdWzbNcBt7ZvUxtonB38v07cDVPkBOtdBPvK=3_Y+rWgg@mail.gmail.com>
Date:   Thu, 15 Dec 2022 11:03:04 +0800
From:   Chengen Du <chengen.du@...onical.com>
To:     Trond Myklebust <trondmy@...merspace.com>
Cc:     Anna Schumaker <anna@...nel.org>,
        Charles Edward Lever <chuck.lever@...cle.com>,
        Jeffrey Layton <jlayton@...nel.org>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] NFS: fix client permission error after adding user to
 permissible group

Hi Trond,

Thanks for your information.

Best regards,
Chengen Du

On Thu, Dec 15, 2022 at 3:42 AM Trond Myklebust <trondmy@...merspace.com> wrote:
>
>
>
> > On Dec 14, 2022, at 03:47, Chengen Du <chengen.du@...onical.com> wrote:
> >
> > The access cache only expires if either NFS_INO_INVALID_ACCESS flag is on
> > or timeout (without delegation).
> > Adding a user to a group in the NFS server will not cause any file
> > attributes to change.
> > The client will encounter permission errors until other file attributes
> > are changed or the memory cache is dropped.
> >
> > Steps to reproduce the issue:
> > 1.[client side] testuser is not part of testgroup
> >  testuser@...etic:~$ ls -ld /mnt/private/
> >  drwxrwx--- 2 root testgroup 4096 Nov 24 08:23 /mnt/private/
> >  testuser@...etic:~$ mktemp -p /mnt/private/
> >  mktemp: failed to create file via template
> >  ‘/mnt/private/tmp.XXXXXXXXXX’: Permission denied
> > 2.[server side] add testuser into testgroup, which has access to folder
> >  root@...etic:~$ usermod -aG testgroup testuser &&
> >  echo `date +'%s'` > /proc/net/rpc/auth.unix.gid/flush
> > 3.[client side] create a file again but still fail
> >  testuser@...etic:~$ mktemp -p /mnt/private/
> >  mktemp: failed to create file via template
> >  ‘/mnt/private/tmp.XXXXXXXXXX’: Permission denied
> >
>
> Thanks, but the correct way to deal with this is to log out and log back in again, the way the POSIX gods intended. See commit 0eb43812c027 ("NFS: Clear the file access cache upon login”).
>
> _________________________________
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trond.myklebust@...merspace.com
>