Re: [PATCH v3 12/13] nfs: copy_file_range needs to strip setuid bits and update timestamps

[Trond Myklebust <trondmy@hammerspace.com>]

On Wed, 2019-05-29 at 22:34 +0300, Amir Goldstein wrote:
> Hi Olga,Anna,Trond
> 
> Could we get an ACK on this patch.
> It is a prerequisite for merging the cross-device copy_file_range
> work.
> 
> It depends on a new helper introduced here:
> https://lore.kernel.org/linux-fsdevel/CAOQ4uxjbcSWX1hUcuXbn8hFH3QYB+5bAC9Z1yCwJdR=T-GGtCg@mail.gmail.com/T/#m1569878c41f39fac3aadb3832a30659c323b582a
> 
> Thanks,
> Amir,
> 
> On Wed, May 29, 2019 at 8:43 PM Amir Goldstein <amir73il@gmail.com>
> wrote:
> > Like ->write_iter(), we update mtime and strip setuid of dst file
> > before
> > copy and like ->read_iter(), we update atime of src file after
> > copy.
> > 
> > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> > ---
> >  fs/nfs/nfs42proc.c | 9 ++++++---
> >  1 file changed, 6 insertions(+), 3 deletions(-)
> > 
> > diff --git a/fs/nfs/nfs42proc.c b/fs/nfs/nfs42proc.c
> > index 5196bfa7894d..c37a8e5116c6 100644
> > --- a/fs/nfs/nfs42proc.c
> > +++ b/fs/nfs/nfs42proc.c
> > @@ -345,10 +345,13 @@ ssize_t nfs42_proc_copy(struct file *src,
> > loff_t pos_src,
> > 
> >         do {
> >                 inode_lock(file_inode(dst));
> > -               err = _nfs42_proc_copy(src, src_lock,
> > -                               dst, dst_lock,
> > -                               &args, &res);
> > +               err = file_modified(dst);
> > +               if (!err)
> > +                       err = _nfs42_proc_copy(src, src_lock,
> > +                                              dst, dst_lock,
> > +                                              &args, &res);
> >                 inode_unlock(file_inode(dst));
> > +               file_accessed(src);
> > 
> >                 if (err >= 0)
> >                         break;
> > --
> > 2.17.1
> > 

Please drop this patch. In the NFS protocol, the client is not expected
to mess with atime or mtime other than when the user explicitly sets it
through a call to utimensat() or similar. The server takes care of any
a/mtime updates as and when the file is read/written to. 

Ditto for suid/sgid clearing.

Motto: "No file_accessed() or file_remove_privs() calls, please. We're
NFS."

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com