RDMA/cma: Don't overwrite sgid_attr after device is released

As part of the cma_dev release, that pointer will be set to NULL.  In case
it happens in rdma_bind_addr() (part of an error flow), the next call to
addr_handler() will have a call to cma_acquire_dev_by_src_ip() which will
overwrite sgid_attr without releasing it.

  WARNING: CPU: 2 PID: 108 at drivers/infiniband/core/cma.c:606 cma_bind_sgid_attr drivers/infiniband/core/cma.c:606 [inline]
  WARNING: CPU: 2 PID: 108 at drivers/infiniband/core/cma.c:606 cma_acquire_dev_by_src_ip+0x470/0x4b0 drivers/infiniband/core/cma.c:649
  CPU: 2 PID: 108 Comm: kworker/u8:1 Not tainted 5.10.0-rc6+ #257
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Workqueue: ib_addr process_one_req
  RIP: 0010:cma_bind_sgid_attr drivers/infiniband/core/cma.c:606 [inline]
  RIP: 0010:cma_acquire_dev_by_src_ip+0x470/0x4b0 drivers/infiniband/core/cma.c:649
  Code: 66 d9 4a ff 4d 8b 6e 10 49 8d bd 1c 08 00 00 e8 b6 d6 4a ff 45 0f b6 bd 1c 08 00 00 41 83 e7 01 e9 49 fd ff ff e8 90 c5 29 ff <0f> 0b e9 80 fe ff ff e8 84 c5 29 ff 4c 89 f7 e8 2c d9 4a ff 4d 8b
  RSP: 0018:ffff8881047c7b40 EFLAGS: 00010293
  RAX: ffff888104789c80 RBX: 0000000000000001 RCX: ffffffff820b8ef8
  RDX: 0000000000000000 RSI: ffffffff820b9080 RDI: ffff88810cd4c998
  RBP: ffff8881047c7c08 R08: ffff888104789c80 R09: ffffed10209f4036
  R10: ffff888104fa01ab R11: ffffed10209f4035 R12: ffff88810cd4c800
  R13: ffff888105750e28 R14: ffff888108f0a100 R15: ffff88810cd4c998
  FS:  0000000000000000(0000) GS:ffff888119c00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000000000 CR3: 0000000104e60005 CR4: 0000000000370ea0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   addr_handler+0x266/0x350 drivers/infiniband/core/cma.c:3190
   process_one_req+0xa3/0x300 drivers/infiniband/core/addr.c:645
   process_one_work+0x54c/0x930 kernel/workqueue.c:2272
   worker_thread+0x82/0x830 kernel/workqueue.c:2418
   kthread+0x1ca/0x220 kernel/kthread.c:292
   ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Fixes: ff11c6cd ("RDMA/cma: Introduce and use cma_acquire_dev_by_src_ip()")
Link: https://lore.kernel.org/r/20201213132940.345554-5-leon@kernel.org


Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>