loop0: detected capacity change from 0 to 4096
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WARNING: lock held when returning to user space!
syzkaller #0 Not tainted
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syz.0.15/5950 is leaving the kernel with locks still held!
1 lock held by syz.0.15/5950:
 #0: ffff8880211a8b60 (&lo->lo_mutex){+.+.}-{3:3}, at: loop_set_block_size+0x7c/0x480 drivers/block/loop.c:1490