syzbot hit the following crash on upstream commit
3fd14cdcc05a682b03743683ce3a726898b20555 (Fri Apr 6 19:15:41 2018 +0000)
Merge tag 'mtd/for-4.17' of git://git.infradead.org/linux-mtd
syzbot dashboard link: https://syzkaller.appspot.com/bug?extid=619d9f40141d826b097e

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output: https://syzkaller.appspot.com/x/log.txt?id=4594231414882304 Kernel config: https://syzkaller.appspot.com/x/.config?id=-5813481738265533882
compiler: gcc (GCC) 8.0.1 20180301 (experimental)

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Reported-by: syzbot+619d9f40141d826b0...@syzkaller.appspotmail.com
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8021q: adding VLAN 0 to HW filter on device team0
IPv6: ADDRCONF(NETDEV_UP): team0: link is not ready
8021q: adding VLAN 0 to HW filter on device team0
IPv6: ADDRCONF(NETDEV_UP): team0: link is not ready
8021q: adding VLAN 0 to HW filter on device team0
watchdog: BUG: soft lockup - CPU#1 stuck for 134s! [syz-executor2:10431]
Modules linked in:
irq event stamp: 35856
hardirqs last enabled at (35855): [<ffffffff874a1734>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline] hardirqs last enabled at (35855): [<ffffffff874a1734>] _raw_spin_unlock_irqrestore+0x74/0xc0 kernel/locking/spinlock.c:184 hardirqs last disabled at (35856): [<ffffffff87600901>] interrupt_entry+0xb1/0xf0 arch/x86/entry/entry_64.S:624 softirqs last enabled at (162): [<ffffffff87800778>] __do_softirq+0x778/0xaf5 kernel/softirq.c:311 softirqs last disabled at (95): [<ffffffff81467a61>] invoke_softirq kernel/softirq.c:365 [inline] softirqs last disabled at (95): [<ffffffff81467a61>] irq_exit+0x1d1/0x200 kernel/softirq.c:405
CPU: 1 PID: 10431 Comm: syz-executor2 Not tainted 4.16.0+ #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:783 [inline] RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline] RIP: 0010:_raw_spin_unlock_irqrestore+0xa1/0xc0 kernel/locking/spinlock.c:184
RSP: 0018:ffff880184db7780 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: dffffc0000000000 RBX: 0000000000000282 RCX: 0000000000000000
RDX: 1ffffffff1162e55 RSI: 0000000000000001 RDI: 0000000000000282
RBP: ffff880184db7790 R08: ffffed0035d21962 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801ae90cb08
R13: ffff880184db7810 R14: 0000000000000001 R15: ffff8801cb9a5880
FS:  00007fc943ad8700(0000) GS:ffff8801db100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc943ad7db8 CR3: 00000001b070d000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 spin_unlock_irqrestore include/linux/spinlock.h:365 [inline]
 snd_virmidi_output_trigger+0x522/0x6c0 sound/core/seq/seq_virmidi.c:205
 snd_rawmidi_output_trigger sound/core/rawmidi.c:150 [inline]
 snd_rawmidi_kernel_write1+0x519/0x700 sound/core/rawmidi.c:1288
 snd_rawmidi_write+0x2e2/0xdc0 sound/core/rawmidi.c:1338
 __vfs_write+0x10b/0x880 fs/read_write.c:485
 vfs_write+0x1f8/0x560 fs/read_write.c:549
 ksys_write+0xf9/0x250 fs/read_write.c:598
 SYSC_write fs/read_write.c:610 [inline]
 SyS_write+0x24/0x30 fs/read_write.c:607
 do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287
RIP: 0033:0x455259
RSP: 002b:00007fc943ad7c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fc943ad86d4 RCX: 0000000000455259
RDX: 00000000e78e624c RSI: 0000000020000040 RDI: 0000000000000014
RBP: 000000000072c010 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000006ca R14: 00000000006fd390 R15: 0000000000000002
Code: c7 a8 72 b1 88 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 21 48 83 3d 4e 5b 67 01 00 74 0e 48 89 df 57 9d <0f> 1f 44 00 00 eb bb 0f 0b 0f 0b e8 6f 29 68 fa eb 97 e8 68 29

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