syzbot

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BUG: KCSAN: data-race in mm_update_next_owner / worker_thread

write to 0xffff8881497d102c of 4 bytes by task 11016 on cpu 1:
 set_pf_worker kernel/workqueue.c:2344 [inline]
 worker_thread+0x5a/0xae0 kernel/workqueue.c:2369
 kthread+0x1d0/0x1f0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff8881497d102c of 4 bytes by task 11018 on cpu 0:
 mm_update_next_owner+0x1d9/0x520 kernel/exit.c:388
 exit_mm+0x358/0x450 kernel/exit.c:500
 do_exit+0x3ff/0x1560 kernel/exit.c:812
 do_group_exit+0x19b/0x1a0 kernel/exit.c:922
 __do_sys_exit_group+0xb/0x10 kernel/exit.c:933
 __se_sys_exit_group+0x5/0x10 kernel/exit.c:931
 __x64_sys_exit_group+0x16/0x20 kernel/exit.c:931
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 11018 Comm: syz-executor.2 Not tainted 5.12.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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