WARNING: lock held when returning to user space!

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9d5c0b3a8e1a Linux 4.14.295
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14a0a2c2880000
kernel config: https://syzkaller.appspot.com/x/.config?x=746c079015a92425
dashboard link: https://syzkaller.appspot.com/bug?extid=c0402e6c7700835c76d5
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1665343c880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12f6f49a880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ed6fcf5895a2/disk-9d5c0b3a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/341aa3534116/vmlinux-9d5c0b3a.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/64ccee194a22/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c0402e...@syzkaller.appspotmail.com

F2FS-fs (loop0): invalid crc value
F2FS-fs (loop0): Found nat_bits in checkpoint
F2FS-fs (loop0): Mounted with checkpoint version = 3651456e
================================================
WARNING: lock held when returning to user space!
4.14.295-syzkaller #0 Not tainted
------------------------------------------------
syz-executor912/7972 is leaving the kernel with locks still held!
1 lock held by syz-executor912/7972:
#0: (sb


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