SUNRPC: Fix a deadlock in rpc_client_register()

Commit 384816051ca9125cd54750e59c780c2a2655fa4f (SUNRPC: fix races on
PipeFS MOUNT notifications) introduces a regression when we call
rpc_setup_pipedir() with RPCSEC_GSS as the auth flavour.

By calling rpcauth_create() while holding the sn->pipefs_sb_lock, we
end up deadlocking in gss_pipes_dentries_create_net().
Fix is to register the client and release the mutex before calling
rpcauth_create().

Reported-by: Weston Andros Adamson <dros@netapp.com>
Tested-by: Weston Andros Adamson <dros@netapp.com>
Cc: Stanislav Kinsbursky <skinsbursky@parallels.com>
Cc: <stable@vger.kernel.org> # : 3848160: SUNRPC: fix races on PipeFS MOUNT
Cc: <stable@vger.kernel.org> # : e73f4cc: SUNRPC: split client creation
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 9 insertions, 7 deletions

diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index f0339ae9bf37..aa401560777b 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -290,7 +290,7 @@ static int rpc_client_register(const struct rpc_create_args *args,
         struct rpc_auth *auth;
         struct net *net = rpc_net_ns(clnt);
         struct super_block *pipefs_sb;
-        int err = 0;
+        int err;
 
         pipefs_sb = rpc_get_sb_net(net);
         if (pipefs_sb) {
@@ -299,6 +299,10 @@ static int rpc_client_register(const struct rpc_create_args *args,
                         goto out;
         }
 
+        rpc_register_client(clnt);
+        if (pipefs_sb)
+                rpc_put_sb_net(net);
+
         auth = rpcauth_create(args->authflavor, clnt);
         if (IS_ERR(auth)) {
                 dprintk("RPC:       Couldn't create auth handle (flavor %u)\n",
@@ -306,16 +310,14 @@ static int rpc_client_register(const struct rpc_create_args *args,
                 err = PTR_ERR(auth);
                 goto err_auth;
         }
-
-        rpc_register_client(clnt);
+        return 0;
+err_auth:
+        pipefs_sb = rpc_get_sb_net(net);
+        __rpc_clnt_remove_pipedir(clnt);
 out:
         if (pipefs_sb)
                 rpc_put_sb_net(net);
         return err;
-
-err_auth:
-        __rpc_clnt_remove_pipedir(clnt);
-        goto out;
 }
 
 static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, struct rpc_xprt *xprt)