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WARNING: lock held when returning to user space!
4.16.0+ #1 Not tainted
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syzkaller965702/4470 is leaving the kernel with locks still held!
1 lock held by syzkaller965702/4470:
 #0: 00000000cde99e96 (&lo->lo_ctl_mutex/1){+.+.}, at: lo_ioctl+0x8d/0x1ec0 drivers/block/loop.c:1363