==================================================================
BUG: KCSAN: data-race in lo_ioctl / loop_queue_work

write to 0xffff888101988818 of 4 bytes by task 5814 on cpu 0:
 loop_clr_fd drivers/block/loop.c:1330 [inline]
 lo_ioctl+0x4b8/0x11f0 drivers/block/loop.c:1695
 blkdev_ioctl+0x1d0/0x3c0 block/ioctl.c:585
 block_ioctl+0x6d/0x80 fs/block_dev.c:1662
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:1069 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:1055
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:1055
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888101988818 of 4 bytes by task 5816 on cpu 1:
 loop_handle_cmd drivers/block/loop.c:2041 [inline]
 loop_queue_work+0x8d/0x1310 drivers/block/loop.c:2064
 kthread_worker_fn+0x280/0x4d0 kernel/kthread.c:756
 loop_kthread_worker_fn+0x3e/0x50 drivers/block/loop.c:933
 kthread+0x1d0/0x1f0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

value changed: 0x00000000 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 5816 Comm: loop1 Not tainted 5.13.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================