sysv, ipc: fix security-layer leaking

Commit 53dad6d3 ("ipc: fix race with LSMs") updated ipc_rcu_putref()
to receive rcu freeing function but used generic ipc_rcu_free() instead
of msg_rcu_free() which does security cleaning.

Running LTP msgsnd06 with kmemleak gives the following:

  cat /sys/kernel/debug/kmemleak

  unreferenced object 0xffff88003c0a11f8 (size 8):
    comm "msgsnd06", pid 1645, jiffies 4294672526 (age 6.549s)
    hex dump (first 8 bytes):
      1b 00 00 00 01 00 00 00                          ........
    backtrace:
      kmemleak_alloc+0x23/0x40
      kmem_cache_alloc_trace+0xe1/0x180
      selinux_msg_queue_alloc_security+0x3f/0xd0
      security_msg_queue_alloc+0x2e/0x40
      newque+0x4e/0x150
      ipcget+0x159/0x1b0
      SyS_msgget+0x39/0x40
      entry_SYSCALL_64_fastpath+0x13/0x8f

Manfred Spraul suggested to fix sem.c as well and Davidlohr Bueso to
only use ipc_rcu_free in case of security allocation failure in newary()

Fixes: 53dad6d3 ("ipc: fix race with LSMs")
Link: http://lkml.kernel.org/r/1470083552-22966-1-git-send-email-fabf@skynet.be


Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: <stable@vger.kernel.org>	[3.12+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>