diff options
| author | Trond Myklebust | 2012-10-23 13:51:58 -0400 |
|---|---|---|
| committer | Trond Myklebust | 2012-10-24 10:46:22 -0400 |
| commit | a4ee8d978e47e79d536226dccb48991f70091168 (patch) | |
| tree | 5c85033eae24348ec07dc9a0a3ddbb25141153bb | |
| parent | f878b657ce8e7d3673afe48110ec208a29e38c4a (diff) | |
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 <nix@esperi.org.uk>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org
| -rw-r--r-- | fs/lockd/mon.c | 43 |
1 files changed, 26 insertions, 17 deletions
diff --git a/fs/lockd/mon.c b/fs/lockd/mon.c index e4fb3ba5a58a..fe695603e395 100644 --- a/fs/lockd/mon.c +++ b/fs/lockd/mon.c @@ -85,29 +85,38 @@ static struct rpc_clnt *nsm_create(struct net *net) return rpc_create(&args); } +static struct rpc_clnt *nsm_client_set(struct lockd_net *ln, + struct rpc_clnt *clnt) +{ + spin_lock(&ln->nsm_clnt_lock); + if (ln->nsm_users == 0) { + if (clnt == NULL) + goto out; + ln->nsm_clnt = clnt; + } + clnt = ln->nsm_clnt; + ln->nsm_users++; +out: + spin_unlock(&ln->nsm_clnt_lock); + return clnt; +} + 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); - if (ln->nsm_users) { - ln->nsm_users++; - clnt = ln->nsm_clnt; - spin_unlock(&ln->nsm_clnt_lock); + clnt = nsm_client_set(ln, NULL); + if (clnt != NULL) goto out; - } - 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; - } - mutex_unlock(&nsm_create_mutex); + clnt = new = nsm_create(net); + if (IS_ERR(clnt)) + goto out; + + clnt = nsm_client_set(ln, new); + if (clnt != new) + rpc_shutdown_client(new); out: return clnt; } |