syzbot

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BUG: KCSAN: data-race in d_set_mounted / dput

write to 0xffff888034819000 of 4 bytes by task 25583 on cpu 0:
 d_set_mounted+0xfc/0x190 fs/dcache.c:1492
 get_mountpoint+0x1be/0x300 fs/namespace.c:755
 lock_mount+0x86/0x1d0 fs/namespace.c:2224
 do_new_mount_fc fs/namespace.c:2846 [inline]
 do_new_mount fs/namespace.c:2905 [inline]
 path_mount+0x18a4/0x1c00 fs/namespace.c:3233
 do_mount fs/namespace.c:3246 [inline]
 __do_sys_mount fs/namespace.c:3454 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3431
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3431
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888034819000 of 4 bytes by task 25575 on cpu 1:
 fast_dput fs/dcache.c:747 [inline]
 dput+0x34/0x430 fs/dcache.c:873
 path_put fs/namei.c:546 [inline]
 terminate_walk+0x109/0x270 fs/namei.c:645
 path_lookupat+0x2f3/0x570 fs/namei.c:2439
 filename_lookup+0xff/0x390 fs/namei.c:2455
 user_path_at_empty+0x3b/0x50 fs/namei.c:2735
 user_path_at include/linux/namei.h:60 [inline]
 vfs_statx+0x98/0x290 fs/stat.c:195
 vfs_fstatat fs/stat.c:217 [inline]
 vfs_stat include/linux/fs.h:3236 [inline]
 __do_sys_newstat fs/stat.c:359 [inline]
 __se_sys_newstat+0x46/0x250 fs/stat.c:355
 __x64_sys_newstat+0x2d/0x40 fs/stat.c:355
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 25575 Comm: syz-executor.1 Not tainted 5.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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