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BUG: KCSAN: data-race in d_set_mounted / dput

write to 0xffff8881209e8e40 of 4 bytes by task 24624 on cpu 1:
 d_set_mounted+0x18e/0x1b0 fs/dcache.c:1440
 get_mountpoint+0x135/0x2f0 fs/namespace.c:724
 lock_mount+0x9a/0x1a0 fs/namespace.c:2142
 do_loopback fs/namespace.c:2291 [inline]
 do_mount+0xa7b/0x1590 fs/namespace.c:3135
 __do_sys_mount fs/namespace.c:3350 [inline]
 __se_sys_mount fs/namespace.c:3327 [inline]
 __x64_sys_mount+0x12b/0x1a0 fs/namespace.c:3327
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881209e8e40 of 4 bytes by task 24629 on cpu 0:
 fast_dput fs/dcache.c:727 [inline]
 dput+0x4b/0x700 fs/dcache.c:846
 cleanup_mnt+0x268/0x330 fs/namespace.c:1101
 __cleanup_mnt+0x1c/0x30 fs/namespace.c:1109
 task_work_run+0xba/0x120 kernel/task_work.c:123
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2ae/0x2c0 arch/x86/entry/common.c:165
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:279 [inline]
 do_syscall_64+0x38b/0x3b0 arch/x86/entry/common.c:305
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 24629 Comm: syz-executor.3 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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