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 --cc fs/nfs/nfs4proc.c
Simple merge

diff --cc include/linux/nfs_xdr.h
Simple merge