NFSv4: Fix memory corruption in nfs4_proc_open_confirm

nfs41_wake_and_assign_slot() relies on the task->tk_msg.rpc_argp and
task->tk_msg.rpc_resp always pointing to the session sequence arguments.

nfs4_proc_open_confirm tries to pull a fast one by reusing the open
sequence structure, thus causing corruption of the NFSv4 slot table.

Cc: stable@vger.kernel.org # 3.12+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 42da6af..2da6a69 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1620,15 +1620,15 @@
 {
 	struct nfs4_opendata *data = calldata;
 
-	nfs40_setup_sequence(data->o_arg.server, &data->o_arg.seq_args,
-				&data->o_res.seq_res, task);
+	nfs40_setup_sequence(data->o_arg.server, &data->c_arg.seq_args,
+				&data->c_res.seq_res, task);
 }
 
 static void nfs4_open_confirm_done(struct rpc_task *task, void *calldata)
 {
 	struct nfs4_opendata *data = calldata;
 
-	nfs40_sequence_done(task, &data->o_res.seq_res);
+	nfs40_sequence_done(task, &data->c_res.seq_res);
 
 	data->rpc_status = task->tk_status;
 	if (data->rpc_status == 0) {
@@ -1686,7 +1686,7 @@
 	};
 	int status;
 
-	nfs4_init_sequence(&data->o_arg.seq_args, &data->o_res.seq_res, 1);
+	nfs4_init_sequence(&data->c_arg.seq_args, &data->c_res.seq_res, 1);
 	kref_get(&data->kref);
 	data->rpc_done = 0;
 	data->rpc_status = 0;