NFSv4: Fix a race in the net namespace mount notification

Since the struct nfs_client gets added to the global nfs_client_list
before it is initialised, it is possible that rpc_pipefs_event can
end up trying to create idmapper entries on such a thing.

The solution is to have the mount notification wait for the
initialisation of each nfs_client to complete, and then to
skip any entries for which the it failed.

Reported-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Stanislav Kinsbursky <skinsbursky@parallels.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index 2eaecf9d8db7..861be75eb165 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -530,9 +530,24 @@ static struct nfs_client *nfs_get_client_for_event(struct net *net, int event)
 	struct nfs_net *nn = net_generic(net, nfs_net_id);
 	struct dentry *cl_dentry;
 	struct nfs_client *clp;
+	int err;
 
+restart:
 	spin_lock(&nn->nfs_client_lock);
 	list_for_each_entry(clp, &nn->nfs_client_list, cl_share_link) {
+		/* Wait for initialisation to finish */
+		if (clp->cl_cons_state == NFS_CS_INITING) {
+			atomic_inc(&clp->cl_count);
+			spin_unlock(&nn->nfs_client_lock);
+			err = nfs_wait_client_init_complete(clp);
+			nfs_put_client(clp);
+			if (err)
+				return NULL;
+			goto restart;
+		}
+		/* Skip nfs_clients that failed to initialise */
+		if (clp->cl_cons_state < 0)
+			continue;
 		if (clp->rpc_ops != &nfs_v4_clientops)
 			continue;
 		cl_dentry = clp->cl_idmap->idmap_pipe->dentry;