linux-kernel - Re: [PATCH] nfsd: Remove write permission from file content

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Message-ID: <20130108151840.GC16343@fieldses.org>
Date:	Tue, 8 Jan 2013 10:18:40 -0500
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Yanchuan Nian <ycnian@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org
Subject: Re: [PATCH] nfsd: Remove write permission from file content

On Sat, Jan 05, 2013 at 12:29:05PM +0800, Yanchuan Nian wrote:
> 2013/1/5 J. Bruce Fields <bfields@...ldses.org>
> 
> > On Fri, Jan 04, 2013 at 07:45:35PM +0800, ycnian@...il.com wrote:
> > > From: Yanchuan Nian <ycnian@...il.com>
> > >
> > > The write function doesn't be implemented in file content, and it's
> > meaningless
> > > to write data into this file directly. Remove write permission from it.
> >
> > So does it really matter either way?
> >
> No, it doesn't matter. I saw that nfs-utils communicates with nfsd through
> proc fs, so I tried to update the cache by writing data to proc fs
> directly. I found the format of "channel" and "flush" in nfs-utils, but I
> couldn't find the format of "content", so I read the sunrpc source code,
> and found that the write function doesn't be implemented, but the write
> permission is set when registering into proc fs. I also found that
> "content" in pipe fs doesn't have write permission.

OK, so if it had been read-only it might have saved you a little
confusion.  Fair enough.

--b.

> 
> >
> > OK, applying, but I wonder.
> >
> > --b.
> >
> > >
> > > Signed-off-by: Yanchuan Nian <ycnian@...il.com>
> > > ---
> > >  net/sunrpc/cache.c |    2 +-
> > >  1 files changed, 1 insertions(+), 1 deletions(-)
> > >
> > > diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
> > > index 9afa439..9f84703 100644
> > > --- a/net/sunrpc/cache.c
> > > +++ b/net/sunrpc/cache.c
> > > @@ -1614,7 +1614,7 @@ static int create_cache_proc_entries(struct
> > cache_detail *cd, struct net *net)
> > >                       goto out_nomem;
> > >       }
> > >       if (cd->cache_show) {
> > > -             p = proc_create_data("content", S_IFREG|S_IRUSR|S_IWUSR,
> > > +             p = proc_create_data("content", S_IFREG|S_IRUSR,
> > >                               cd->u.procfs.proc_ent,
> > >                               &content_file_operations_procfs, cd);
> > >               cd->u.procfs.content_ent = p;
> > > --
> > > 1.7.4.4
> > >
> >
--
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