Return-Path: Received: from fieldses.org ([173.255.197.46]:54496 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756133AbcETPea (ORCPT ); Fri, 20 May 2016 11:34:30 -0400 Date: Fri, 20 May 2016 11:34:28 -0400 To: Jeff Layton Cc: =?utf-8?B?VG9tw6HFoQ==?= Trnka , linux-nfs@vger.kernel.org Subject: Re: [PATCH] sunrpc: fix stripping of padded MIC tokens Message-ID: <20160520153428.GE2119@fieldses.org> References: <38521704.8vjDAt0XQs@mintaka.ncbr.muni.cz> <1463758273.14305.1.camel@poochiereds.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 In-Reply-To: <1463758273.14305.1.camel@poochiereds.net> From: bfields@fieldses.org (J. Bruce Fields) Sender: linux-nfs-owner@vger.kernel.org List-ID: 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 > > --- > >  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 Thanks! Applying for 4.6 and stable. --b.