WARNING in cma_exit_net

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    e3ecb83e Add linux-next specific files for 20190401
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13bc36cd200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=db6c9f2bfeb91a99
dashboard link: https://syzkaller.appspot.com/bug?extid=2e3e485d5697ea610460
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2e3e485d5697ea610460@xxxxxxxxxxxxxxxxxxxxxxxxx

WARNING: CPU: 1 PID: 7 at drivers/infiniband/core/cma.c:4674  
cma_exit_net+0x327/0x390 drivers/infiniband/core/cma.c:4674
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 7 Comm: kworker/u4:0 Not tainted 5.1.0-rc2-next-20190401 #15
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 panic+0x2cb/0x65c kernel/panic.c:214
 __warn.cold+0x20/0x45 kernel/panic.c:571
 report_bug+0x263/0x2b0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:179 [inline]
 fixup_bug arch/x86/kernel/traps.c:174 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
RIP: 0010:cma_exit_net+0x327/0x390 drivers/infiniband/core/cma.c:4674
Code: 00 48 c7 c7 c0 4e ea 87 c6 05 89 86 4a 04 01 e8 ba cc 46 fc e9 c8 fd  
ff ff e8 25 6c 5f fc 0f 0b e9 d7 fe ff ff e8 19 6c 5f fc <0f> 0b e8 12 6c  
5f fc 48 8d 65 e8 5b 41 5c 41 5d 5d c3 e8 02 6c 5f
RSP: 0000:ffff8880aa267bf0 EFLAGS: 00010293
RAX: ffff8880aa2581c0 RBX: ffff8880a538d500 RCX: 1ffff1101544b146
RDX: 0000000000000000 RSI: ffffffff85111537 RDI: ffff8880a538d618
RBP: ffff8880aa267c08 R08: ffff8880aa2581c0 R09: 0000000000000004
R10: ffffed1015d25bcf R11: ffff8880ae92de7b R12: 0000000000000001
R13: ffff8880a90e84c0 R14: ffffffff891e29f8 R15: dffffc0000000000
 ops_exit_list.isra.0+0xb0/0x160 net/core/net_namespace.c:153
 cleanup_net+0x3fb/0x960 net/core/net_namespace.c:552
 process_one_work+0x98e/0x1790 kernel/workqueue.c:2270
 worker_thread+0x98/0xe40 kernel/workqueue.c:2416
 kthread+0x357/0x430 kernel/kthread.c:254
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Kernel Offset: disabled
Rebooting in 86400 seconds..


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