Return-Path: Received: from mail-qk0-f175.google.com ([209.85.220.175]:36003 "EHLO mail-qk0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751388AbcHGWWk (ORCPT ); Sun, 7 Aug 2016 18:22:40 -0400 Received: by mail-qk0-f175.google.com with SMTP id v123so174676085qkh.3 for ; Sun, 07 Aug 2016 15:22:40 -0700 (PDT) Message-ID: <1470608556.2975.8.camel@redhat.com> Subject: Re: [PATCH v2] nfsd: Fix race between FREE_STATEID and LOCK From: Jeff Layton To: Chuck Lever , linux-nfs@vger.kernel.org Date: Sun, 07 Aug 2016 18:22:36 -0400 In-Reply-To: <20160807185024.11705.10864.stgit@klimt.1015granger.net> References: <20160807185024.11705.10864.stgit@klimt.1015granger.net> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-nfs-owner@vger.kernel.org List-ID: On Sun, 2016-08-07 at 14:53 -0400, Chuck Lever wrote: > When running LTP's nfslock01 test, the Linux client can send a LOCK > and a FREE_STATEID request at the same time. The LOCK uses the same > lockowner as the stateid sent in the FREE_STATEID request. > > The outcome is: > > Frame 115025 C FREE_STATEID stateid 2/A > Frame 115026 C LOCK offset 672128 len 64 > Frame 115029 R FREE_STATEID NFS4_OK > Frame 115030 R LOCK stateid 3/A > Frame 115034 C WRITE stateid 0/A offset 672128 len 64 > Frame 115038 R WRITE NFS4ERR_BAD_STATEID > > In other words, the server returns stateid A in a successful LOCK > reply, but it has already released it. Subsequent uses of the > stateid fail. > > To address this, protect the generation check in nfsd4_free_stateid > with the st_mutex. This should guarantee that only one of two > outcomes occurs: either LOCK returns a fresh valid stateid, or > FREE_STATEID returns NFS4ERR_LOCKS_HELD. > > Reported-by: Alexey Kodanev > Fix-suggested-by: Jeff Layton > Signed-off-by: Chuck Lever > --- >  fs/nfsd/nfs4state.c |   19 ++++++++++++------- >  1 file changed, 12 insertions(+), 7 deletions(-) > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index b921123..07dc1aa 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -4911,19 +4911,20 @@ nfsd4_free_stateid(struct svc_rqst *rqstp, > struct nfsd4_compound_state *cstate, >   ret = nfserr_locks_held; >   break; >   case NFS4_LOCK_STID: > + atomic_inc(&s->sc_count); > + spin_unlock(&cl->cl_lock); > + stp = openlockstateid(s); > + mutex_lock(&stp->st_mutex); >   ret = check_stateid_generation(stateid, &s- > >sc_stateid, 1); >   if (ret) > - break; > - stp = openlockstateid(s); > + goto out_mutex_unlock; >   ret = nfserr_locks_held; >   if (check_for_locks(stp->st_stid.sc_file, >       lockowner(stp->st_stateowner))) > - break; > - WARN_ON(!unhash_lock_stateid(stp)); > - spin_unlock(&cl->cl_lock); > - nfs4_put_stid(s); > + goto out_mutex_unlock; > + release_lock_stateid(stp); >   ret = nfs_ok; > - goto out; > + goto out_mutex_unlock; >   case NFS4_REVOKED_DELEG_STID: >   dp = delegstateid(s); >   list_del_init(&dp->dl_recall_lru); > @@ -4937,6 +4938,10 @@ out_unlock: >   spin_unlock(&cl->cl_lock); >  out: >   return ret; > +out_mutex_unlock: > + mutex_unlock(&stp->st_mutex); > + nfs4_put_stid(s); > + goto out; >  } >   >  static inline int > >  Looks good to me. Reviewed-by: Jeff Layton