WARNING in ib_umad_kill_port

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    304e0242 net_sched: add a temporary refcnt for struct tcin..
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=119dd16de00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8c1e98458335a7d1
dashboard link: https://syzkaller.appspot.com/bug?extid=9627a92b1f9262d5d30c
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+9627a92b1f9262d5d30c@xxxxxxxxxxxxxxxxxxxxxxxxx

------------[ cut here ]------------
sysfs group 'power' not found for kobject 'umad1'
WARNING: CPU: 1 PID: 31308 at fs/sysfs/group.c:279 sysfs_remove_group fs/sysfs/group.c:279 [inline]
WARNING: CPU: 1 PID: 31308 at fs/sysfs/group.c:279 sysfs_remove_group+0x155/0x1b0 fs/sysfs/group.c:270
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 31308 Comm: kworker/u4:10 Not tainted 5.6.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_unbound ib_unregister_work
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x188/0x20d lib/dump_stack.c:118
 panic+0x2e3/0x75c kernel/panic.c:221
 __warn.cold+0x2f/0x35 kernel/panic.c:582
 report_bug+0x27b/0x2f0 lib/bug.c:195
 fixup_bug arch/x86/kernel/traps.c:175 [inline]
 fixup_bug arch/x86/kernel/traps.c:170 [inline]
 do_error_trap+0x12b/0x220 arch/x86/kernel/traps.c:267
 do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286
 invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:sysfs_remove_group fs/sysfs/group.c:279 [inline]
RIP: 0010:sysfs_remove_group+0x155/0x1b0 fs/sysfs/group.c:270
Code: 48 89 d9 49 8b 14 24 48 b8 00 00 00 00 00 fc ff df 48 c1 e9 03 80 3c 01 00 75 41 48 8b 33 48 c7 c7 60 c3 39 88 e8 93 c3 5f ff <0f> 0b eb 95 e8 22 62 cb ff e9 d2 fe ff ff 48 89 df e8 15 62 cb ff
RSP: 0018:ffffc90001d97a60 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffffffff88915620 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff815ca861 RDI: fffff520003b2f3e
RBP: 0000000000000000 R08: ffff8880a78fc2c0 R09: ffffed1015ce66a1
R10: ffffed1015ce66a0 R11: ffff8880ae733507 R12: ffff88808e5ba070
R13: ffffffff88915bc0 R14: ffff88808e5ba008 R15: dffffc0000000000
 dpm_sysfs_remove+0x97/0xb0 drivers/base/power/sysfs.c:794
 device_del+0x18b/0xd30 drivers/base/core.c:2687
 cdev_device_del+0x15/0x80 fs/char_dev.c:570
 ib_umad_kill_port+0x45/0x250 drivers/infiniband/core/user_mad.c:1327
 ib_umad_remove_one+0x18a/0x220 drivers/infiniband/core/user_mad.c:1409
 remove_client_context+0xbe/0x110 drivers/infiniband/core/device.c:724
 disable_device+0x13b/0x230 drivers/infiniband/core/device.c:1270
 __ib_unregister_device+0x91/0x180 drivers/infiniband/core/device.c:1437
 ib_unregister_work+0x15/0x30 drivers/infiniband/core/device.c:1547
 process_one_work+0x965/0x16a0 kernel/workqueue.c:2266
 worker_thread+0x96/0xe20 kernel/workqueue.c:2412
 kthread+0x388/0x470 kernel/kthread.c:268
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Kernel Offset: disabled
Rebooting in 86400 seconds..


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