==================================================================
BUG: KCSAN: data-race in mm_update_next_owner / wb_workfn

write to 0xffff888131c0c02c of 4 bytes by task 6974 on cpu 0:
 wb_workfn+0x78/0x520 fs/fs-writeback.c:2080
 process_one_work+0x3e9/0x8f0 kernel/workqueue.c:2275
 process_scheduled_works kernel/workqueue.c:2337 [inline]
 worker_thread+0x7ff/0xae0 kernel/workqueue.c:2423
 kthread+0x1d0/0x1f0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff888131c0c02c of 4 bytes by task 4186 on cpu 1:
 mm_update_next_owner+0x1d9/0x520 kernel/exit.c:389
 exit_mm+0x358/0x450 kernel/exit.c:501
 do_exit+0x3ff/0x1560 kernel/exit.c:813
 do_group_exit+0xce/0x1a0 kernel/exit.c:923
 get_signal+0xfc3/0x1610 kernel/signal.c:2818
 arch_do_signal_or_restart+0x2a/0x220 arch/x86/kernel/signal.c:789
 handle_signal_work kernel/entry/common.c:147 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x109/0x190 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:301
 do_syscall_64+0x56/0x90 arch/x86/entry/common.c:57
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4186 Comm: syz-executor.0 Not tainted 5.13.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================