Hello,

syzbot hit the following crash on upstream commit
ce380619fab99036f5e745c7a865b21c59f005f6 (Tue Mar 6 04:31:14 2018 +0000)
Merge tag 'please-pull-ia64_misc' of  
git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux

So far this crash happened 3 times on upstream.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

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Reported-by: syzbot+8882c6f4c8feae701eba@syzkaller.appspotmail.com
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kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 4278 Comm: syzkaller771653 Not tainted 4.16.0-rc4+ #343
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__lock_acquire+0xa09/0x3e00 kernel/locking/lockdep.c:3310
RSP: 0018:ffff8801b0477370 EFLAGS: 00010002
RAX: dffffc0000000000 RBX: 0000000000000001 RCX: 0000000000000000
RDX: 0000000000000046 RSI: 0000000000000000 RDI: ffffffff86ec9920
RBP: ffff8801b0477700 R08: ffffffff841cb939 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000230 R12: 0000000000000000
R13: 0000000000000001 R14: 0000000000000000 R15: ffff8801b09f8080
FS:  00007f9804bd9700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd44e116000 CR3: 00000001b77dc005 CR4: 00000000001606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
  _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
  cma_exch drivers/infiniband/core/cma.c:461 [inline]
  rdma_destroy_id+0xa9/0xda0 drivers/infiniband/core/cma.c:1660
  ucma_destroy_id+0x2e9/0x4c0 drivers/infiniband/core/ucma.c:606
  ucma_write+0x2d6/0x3d0 drivers/infiniband/core/ucma.c:1627
  __vfs_write+0xef/0x970 fs/read_write.c:480
  vfs_write+0x189/0x510 fs/read_write.c:544
  SYSC_write fs/read_write.c:589 [inline]
  SyS_write+0xef/0x220 fs/read_write.c:581
  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x449639
RSP: 002b:00007f9804bd8da8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000006dac5c RCX: 0000000000449639
RDX: 00000000000000a4 RSI: 0000000020000000 RDI: 00000000000001b4
RBP: 00000000006dac58 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 006d635f616d6472
R13: 2f646e6162696e69 R14: 666e692f7665642f R15: 0000000000000007
Code: 81 c4 60 03 00 00 44 89 d0 5b 41 5a 41 5c 41 5d 41 5e 41 5f 5d 49 8d  
62 f8 c3 4c 89 da 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00  
0f 85 0a 33 00 00 49 81 3b 60 ed 9f 87 41 bd 00 00
RIP: __lock_acquire+0xa09/0x3e00 kernel/locking/lockdep.c:3310 RSP:  
ffff8801b0477370
---[ end trace 885cef83eddc104c ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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