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.
--b.
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