On Fri, May 20, 2016 at 11:34:28AM -0400, J. Bruce Fields wrote:
> On Fri, May 20, 2016 at 11:31:13AM -0400, Jeff Layton wrote:
> > On Fri, 2016-05-20 at 16:41 +0200, Tomáš Trnka wrote:
> > > The length of the GSS MIC token need not be a multiple of four bytes.
> > > It is then padded by XDR to a multiple of 4 B, but unwrap_integ_data()
> > > would previously only trim mic.len + 4 B. The remaining up to three
> > > bytes would then trigger a check in nfs4svc_decode_compoundargs(),
> > > leading to a "garbage args" error and mount failure:
> > >
> > > nfs4svc_decode_compoundargs: compound not properly padded!
> > > nfsd: failed to decode arguments!
> > >
> > > This would prevent older clients using the pre-RFC 4121 MIC format
> > > (37-byte MIC including a 9-byte OID) from mounting exports from v3.9+
> > > servers using krb5i.
> > >
> > > The trimming was introduced by commit 4c190e2f913f ("sunrpc: trim off
> > > trailing checksum before returning decrypted or integrity authenticated
> > > buffer").
> > >
> > > Signed-off-by: Tomáš Trnka <ttrnka@xxxxxxxxxxxx>
> > > ---
> > > net/sunrpc/auth_gss/svcauth_gss.c | 4 ++--
> > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/net/sunrpc/auth_gss/svcauth_gss.c
> > > b/net/sunrpc/auth_gss/svcauth_gss.c
> > > index 1095be9..4605dc7 100644
> > > --- a/net/sunrpc/auth_gss/svcauth_gss.c
> > > +++ b/net/sunrpc/auth_gss/svcauth_gss.c
> > > @@ -857,8 +857,8 @@ unwrap_integ_data(struct svc_rqst *rqstp, struct xdr_buf
> > > *buf, u32 seq, struct g
> > > goto out;
> > > if (svc_getnl(&buf->head[0]) != seq)
> > > goto out;
> > > - /* trim off the mic at the end before returning */
> > > - xdr_buf_trim(buf, mic.len + 4);
> > > + /* trim off the mic and padding at the end before returning */
> > > + xdr_buf_trim(buf, round_up_to_quad(mic.len) + 4);
> > > stat = 0;
> > > out:
> > > kfree(mic.data);
> >
> > Looks reasonable:
> >
> > Acked-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
>
> Thanks! Applying for 4.6 and stable.
(Err, 4.7. All these version numbers run into each other...).
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