Re: linux-3.14 nfsd regression

Jeff Layton
2014-04-04T14:08:07Z

On Fri, 4 Apr 2014 09:58:43 -0400
"J. Bruce Fields" <bfields@fieldses.org> wrote:

> On Thu, Apr 03, 2014 at 07:21:46PM -0400, Jeff Layton wrote:
> > So according to the RFC you have to encode both the mode bits and the
> > ftype for v2. The type bits seem to be removed from the mode in NFSv3
> > though, so perhaps we should only be doing that masking in versions
> > above v2?
>
> Right, the problematic patch applied the same mask in both v2 and v3
> cases, so I'm reverting just the v2 part (see below).
>
> > With a quick check, it looks like the v3 code doesn't rely on those bits
> > and I imagine v4 doesn't either.
> >
> > It might also be nice to have the client v2 decode_fattr function to
> > throw a warning if the server sends us mismatched type bits and ftype
> > values. That would have helped us catch this sooner...
>
> Yes, that might be a reasonable thing to do, though I don't know if it's
> worth it.
>
> --b.
>
> commit 35a8dff14e76c00e5b52140290cfb498dc2454a0
> Author: J. Bruce Fields <bfields@redhat.com>
> Date: Thu Apr 3 15:10:35 2014 -0400
>
> nfsd: revert v2 half of "nfsd: don't return high mode bits"
>
> This reverts the part of commit 6e14b46b91fee8a049b0940333ce13a820beaaa5
> that changes NFSv2 behavior.
>
> Mark Lord found that it broke nfs-root for Linux clients, because it
> broke NFSv2.
>
> In fact, from RFC 1094:
>
> "Notice that the file type is specified both in the mode bits
> and in the file type. This is really a bug in the protocol and
> will be fixed in future versions."
>
> So NFSv2 clients really are expected to depend on the high bits of the
> mode.
>
> Cc: stable@kernel.org
> Reported-by: Mark Lord <mlord@pobox.com>
> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
>
> diff --git a/fs/nfsd/nfsxdr.c b/fs/nfsd/nfsxdr.c
> index b17d932..9c769a4 100644
> --- a/fs/nfsd/nfsxdr.c
> +++ b/fs/nfsd/nfsxdr.c
> @@ -152,7 +152,7 @@ encode_fattr(struct svc_rqst *rqstp, __be32 *p, struct svc_fh *fhp,
> type = (stat->mode & S_IFMT);
>
> *p++ = htonl(nfs_ftypes[type >> 12]);
> - *p++ = htonl((u32) (stat->mode & S_IALLUGO));
> + *p++ = htonl((u32) stat->mode);
> *p++ = htonl((u32) stat->nlink);
> *p++ = htonl((u32) from_kuid(&init_user_ns, stat->uid));
> *p++ = htonl((u32) from_kgid(&init_user_ns, stat->gid));

Looks right...

Reviewed-by: Jeff Layton <jlayton@redhat.com>