From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:56137 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964936AbcIVRcz (ORCPT ); Thu, 22 Sep 2016 13:32:55 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jeff Layton , Chuck Lever , "J. Bruce Fields" Subject: [PATCH 4.4 015/118] nfsd: Close race between nfsd4_release_lockowner and nfsd4_lock Date: Thu, 22 Sep 2016 19:28:35 +0200 Message-Id: <20160922172939.404393523@linuxfoundation.org> In-Reply-To: <20160922172938.643879685@linuxfoundation.org> References: <20160922172938.643879685@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chuck Lever commit 885848186fbc2d1d8fb6d2fdc2156638ae289a46 upstream. nfsd4_release_lockowner finds a lock owner that has no lock state, and drops cl_lock. Then release_lockowner picks up cl_lock and unhashes the lock owner. During the window where cl_lock is dropped, I don't see anything preventing a concurrent nfsd4_lock from finding that same lock owner and adding lock state to it. Move release_lockowner() into nfsd4_release_lockowner and hang onto the cl_lock until after the lock owner's state cannot be found again. Found by inspection, we don't currently have a reproducer. Fixes: 2c41beb0e5cf ("nfsd: reduce cl_lock thrashing in ... ") Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: J. Bruce Fields Signed-off-by: Greg Kroah-Hartman --- fs/nfsd/nfs4state.c | 40 +++++++++++++++++----------------------- 1 file changed, 17 insertions(+), 23 deletions(-) --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -1200,27 +1200,6 @@ free_ol_stateid_reaplist(struct list_hea } } -static void release_lockowner(struct nfs4_lockowner *lo) -{ - struct nfs4_client *clp = lo->lo_owner.so_client; - struct nfs4_ol_stateid *stp; - struct list_head reaplist; - - INIT_LIST_HEAD(&reaplist); - - spin_lock(&clp->cl_lock); - unhash_lockowner_locked(lo); - while (!list_empty(&lo->lo_owner.so_stateids)) { - stp = list_first_entry(&lo->lo_owner.so_stateids, - struct nfs4_ol_stateid, st_perstateowner); - WARN_ON(!unhash_lock_stateid(stp)); - put_ol_stateid_locked(stp, &reaplist); - } - spin_unlock(&clp->cl_lock); - free_ol_stateid_reaplist(&reaplist); - nfs4_put_stateowner(&lo->lo_owner); -} - static void release_open_stateid_locks(struct nfs4_ol_stateid *open_stp, struct list_head *reaplist) { @@ -5952,6 +5931,7 @@ nfsd4_release_lockowner(struct svc_rqst __be32 status; struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id); struct nfs4_client *clp; + LIST_HEAD (reaplist); dprintk("nfsd4_release_lockowner clientid: (%08x/%08x):\n", clid->cl_boot, clid->cl_id); @@ -5982,9 +5962,23 @@ nfsd4_release_lockowner(struct svc_rqst nfs4_get_stateowner(sop); break; } + if (!lo) { + spin_unlock(&clp->cl_lock); + return status; + } + + unhash_lockowner_locked(lo); + while (!list_empty(&lo->lo_owner.so_stateids)) { + stp = list_first_entry(&lo->lo_owner.so_stateids, + struct nfs4_ol_stateid, + st_perstateowner); + WARN_ON(!unhash_lock_stateid(stp)); + put_ol_stateid_locked(stp, &reaplist); + } spin_unlock(&clp->cl_lock); - if (lo) - release_lockowner(lo); + free_ol_stateid_reaplist(&reaplist); + nfs4_put_stateowner(&lo->lo_owner); + return status; }