On Tue, 2012-10-23 at 17:44 +0000, Myklebust, Trond wrote: > You can't hold a spinlock while sleeping. Both mutex_lock() and nsm_create() > can definitely sleep. > > The correct way to do this is to grab the spinlock and recheck the value of > ln->nsm_users inside the 'if (!IS_ERR())' condition. If it is still zero, > bump it and set ln->nsm_clnt, otherwise bump it, get the existing > ln->nsm_clnt and call rpc_shutdown_clnt() on the redundant nsm client after > dropping the spinlock. > > Cheers > Trond
Can you please check if the following patch fixes the issue? Cheers Trond 8<-------------------------------------------------------- From 44a070455d246e09de0cefc8875833f21ca655e8 Mon Sep 17 00:00:00 2001 From: Trond Myklebust <trond.mykleb...@netapp.com> Date: Tue, 23 Oct 2012 13:51:58 -0400 Subject: [PATCH] LOCKD: fix races in nsm_client_get Commit e9406db20fecbfcab646bad157b4cfdc7cadddfb (lockd: per-net NSM client creation and destruction helpers introduced) contains a nasty race on initialisation of the per-net NSM client because it doesn't check whether or not the client is set after grabbing the nsm_create_mutex. Reported-by: Nix <n...@esperi.org.uk> Signed-off-by: Trond Myklebust <trond.mykleb...@netapp.com> --- fs/lockd/mon.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/fs/lockd/mon.c b/fs/lockd/mon.c index e4fb3ba..9755603 100644 --- a/fs/lockd/mon.c +++ b/fs/lockd/mon.c @@ -88,7 +88,7 @@ static struct rpc_clnt *nsm_create(struct net *net) static struct rpc_clnt *nsm_client_get(struct net *net) { static DEFINE_MUTEX(nsm_create_mutex); - struct rpc_clnt *clnt; + struct rpc_clnt *clnt, *new; struct lockd_net *ln = net_generic(net, lockd_net_id); spin_lock(&ln->nsm_clnt_lock); @@ -101,11 +101,19 @@ static struct rpc_clnt *nsm_client_get(struct net *net) spin_unlock(&ln->nsm_clnt_lock); mutex_lock(&nsm_create_mutex); - clnt = nsm_create(net); - if (!IS_ERR(clnt)) { - ln->nsm_clnt = clnt; - smp_wmb(); - ln->nsm_users = 1; + new = nsm_create(net); + clnt = new; + if (!IS_ERR(new)) { + spin_lock(&ln->nsm_clnt_lock); + if (!ln->nsm_users) { + ln->nsm_clnt = new; + new = NULL; + } + clnt = ln->nsm_clnt; + ln->nsm_users++; + spin_unlock(&ln->nsm_clnt_lock); + if (new) + rpc_shutdown_client(new); } mutex_unlock(&nsm_create_mutex); out: -- 1.7.11.7 -- Trond Myklebust Linux NFS client maintainer NetApp trond.mykleb...@netapp.com www.netapp.com N�����r��y����b�X��ǧv�^�){.n�+����{����zX����ܨ}���Ơz�&j:+v�������zZ+��+zf���h���~����i���z��w���?�����&�)ߢf��^jǫy�m��@A�a��� 0��h���i