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BUG: KCSAN: data-race in d_set_mounted / dput

write to 0xffff888131741cc0 of 4 bytes by task 31442 on cpu 1:
 d_set_mounted+0x112/0x190 fs/dcache.c:1459
 get_mountpoint+0x1ac/0x2f0 fs/namespace.c:740
 attach_recursive_mnt+0x9a/0x1180 fs/namespace.c:2114
 graft_tree fs/namespace.c:2237 [inline]
 do_loopback fs/namespace.c:2365 [inline]
 path_mount+0x1326/0x1c00 fs/namespace.c:3197
 do_mount fs/namespace.c:3216 [inline]
 __do_sys_mount fs/namespace.c:3424 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3401
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3401
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888131741cc0 of 4 bytes by task 5078 on cpu 0:
 fast_dput fs/dcache.c:746 [inline]
 dput+0x2f/0x420 fs/dcache.c:865
 path_put fs/namei.c:496 [inline]
 terminate_walk+0x218/0x260 fs/namei.c:597
 path_lookupat+0x2c5/0x550 fs/namei.c:2350
 filename_lookup+0xf2/0x380 fs/namei.c:2366
 user_path_at_empty+0x3b/0x50 fs/namei.c:2646
 user_path_at include/linux/namei.h:59 [inline]
 vfs_statx+0xaf/0x2a0 fs/stat.c:202
 vfs_lstat include/linux/fs.h:3115 [inline]
 __do_sys_newlstat fs/stat.c:374 [inline]
 __se_sys_newlstat+0x46/0x250 fs/stat.c:368
 __x64_sys_newlstat+0x2d/0x40 fs/stat.c:368
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 5078 Comm: systemd-udevd Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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