RDMA/srpt: Fix a use-after-free

RDMA/srpt: Fix a use-after-free

Change the LIO port members inside struct srpt_port from regular members
into pointers. Allocate the LIO port data structures from inside
srpt_make_tport() and free these from inside srpt_make_tport(). Keep
struct srpt_device as long as either an RDMA port or a LIO target port is
associated with it. This patch decouples the lifetime of struct srpt_port
(controlled by the RDMA core) and struct srpt_port_id (controlled by LIO).
This patch fixes the following KASAN complaint:

  BUG: KASAN: use-after-free in srpt_enable_tpg+0x31/0x70 [ib_srpt]
  Read of size 8 at addr ffff888141cc34b8 by task check/5093

  Call Trace:
   <TASK>
   show_stack+0x4e/0x53
   dump_stack_lvl+0x51/0x66
   print_address_description.constprop.0.cold+0xea/0x41e
   print_report.cold+0x90/0x205
   kasan_report+0xb9/0xf0
   __asan_load8+0x69/0x90
   srpt_enable_tpg+0x31/0x70 [ib_srpt]
   target_fabric_tpg_base_enable_store+0xe2/0x140 [target_core_mod]
   configfs_write_iter+0x18b/0x210
   new_sync_write+0x1f2/0x2f0
   vfs_write+0x3e3/0x540
   ksys_write+0xbb/0x140
   __x64_sys_write+0x42/0x50
   do_syscall_64+0x34/0x80
   entry_SYSCALL_64_after_hwframe+0x46/0xb0
   </TASK>

Link: https://lore.kernel.org/r/20220727193415.1583860-4-bvanassche@acm.org
Reported-by: Li Zhijian <lizhijian@fujitsu.com>
Tested-by: Li Zhijian <lizhijian@fujitsu.com>
Fixes: a42d985bd5b2 ("ib_srpt: Initial SRP Target merge for v3.3-rc1")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>