syzbot

EXT4-fs (loop4): VFS: Can't find ext4 filesystem
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BUG: KCSAN: data-race in exit_signals / kthread_unpark

write to 0xffff8881212020a4 of 4 bytes by task 28164 on cpu 1:
 exit_signals+0x13b/0x490 kernel/signal.c:2822
 do_exit+0x18b/0x18f0 kernel/exit.c:763
 kthread+0x17f/0x200 drivers/block/aoe/aoecmd.c:1242
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff8881212020a4 of 4 bytes by task 28162 on cpu 0:
 to_kthread kernel/kthread.c:75 [inline]
 kthread_unpark+0x24/0xe0 kernel/kthread.c:474
 kthread_stop+0x97/0x2d0 kernel/kthread.c:557
 loop_unprepare_queue drivers/block/loop.c:883 [inline]
 __loop_clr_fd+0x3ad/0x720 drivers/block/loop.c:1145
 loop_clr_fd drivers/block/loop.c:1224 [inline]
 lo_ioctl+0x24c/0xc80 drivers/block/loop.c:1593
 __blkdev_driver_ioctl block/ioctl.c:304 [inline]
 blkdev_ioctl+0x979/0x1160 block/ioctl.c:606
 block_ioctl+0x95/0xc0 fs/block_dev.c:1954
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x991/0xc60 fs/ioctl.c:696
 ksys_ioctl+0xbd/0xe0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x4c/0x60 fs/ioctl.c:718
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 28162 Comm: syz-executor.4 Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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