Hello,

syzbot hit the following crash on upstream commit
8f5fd927c3a7576d57248a2d7a0861c3f2795973 (Fri Mar 16 20:37:42 2018 +0000)
Merge tag 'for-4.16-rc5-tag' of  
git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=2a2c48fc189ed5125b9c

So far this crash happened 2 times on upstream.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
.config is attached.
compiler: gcc (GCC) 7.1.1 20170620

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2a2c48fc189ed5125b9c@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

audit: type=1400 audit(1521277737.761:7): avc:  denied  { map } for   
pid=4234 comm="syzkaller098821" path="/root/syzkaller098821515" dev="sda1"  
ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023  
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
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: 0 PID: 4236 Comm: syzkaller098821 Not tainted 4.16.0-rc5+ #357
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:rdma_addr_size+0x1e/0x70 drivers/infiniband/core/addr.c:197
RSP: 0018:ffff8801b9cc7870 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000020 RCX: ffffffff841374bd
RDX: 0000000000000004 RSI: 0000000000000000 RDI: 0000000000000020
RBP: ffff8801b9cc7878 R08: ffffed0037398f3a R09: ffff8801b9cc78c0
R10: 0000000000000022 R11: ffffed0037398f39 R12: ffff8801b9cc78c0
R13: ffff8801b260a1f0 R14: ffff8801b9cc7a00 R15: 0000000000000020
FS:  00007fd9212b2700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd9212b1e78 CR3: 00000001b7af4006 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  ucma_query_addr.isra.7+0xce/0x4f0 drivers/infiniband/core/ucma.c:871
  ucma_query+0x1bb/0x230 drivers/infiniband/core/ucma.c:991
  ucma_write+0x2d6/0x3d0 drivers/infiniband/core/ucma.c:1633
  __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: 0033:0x445959
RSP: 002b:00007fd9212b1da8 EFLAGS: 00000297 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000006dac5c RCX: 0000000000445959
RDX: 0000000000000018 RSI: 00000000200022c0 RDI: 0000000000000003
RBP: 00000000006dac58 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000297 R12: 006d635f616d6472
R13: 2f646e6162696e69 R14: 666e692f7665642f R15: 0000000000000008
Code: 29 e4 95 fd e9 f8 fe ff ff 90 90 90 90 55 48 89 e5 53 48 89 fb e8 e3  
a2 5d fd 48 89 da 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <0f> b6 14 02  
48 89 d8 83 e0 07 83 c0 01 38 d0 7c 04 84 d2 75 2f
RIP: rdma_addr_size+0x1e/0x70 drivers/infiniband/core/addr.c:197 RSP:  
ffff8801b9cc7870
---[ end trace 6c753cc522bb59ed ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzkaller@googlegroups.com.

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is  
merged
into any tree, please reply to this email with:
#syz fix: exact-commit-title
If you want to test a patch for this bug, please reply with:
#syz test: git://repo/address.git branch
and provide the patch inline or as an attachment.
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug  
report.
Note: all commands must start from beginning of the line in the email body.