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BUG: KCSAN: data-race in __follow_mount_rcu / d_set_mounted

read to 0xffff8881006ac6c0 of 4 bytes by task 3000 on cpu 1:
 __follow_mount_rcu+0x19a/0x2f0 fs/namei.c:1659
 handle_mounts fs/namei.c:1685 [inline]
 step_into_slowpath+0x30c/0x4c0 fs/namei.c:2051
 step_into fs/namei.c:2099 [inline]
 walk_component fs/namei.c:2235 [inline]
 link_path_walk+0x974/0xe30 fs/namei.c:2597
 path_lookupat+0x8c/0x500 fs/namei.c:2753
 filename_lookup+0x190/0x390 fs/namei.c:2783
 do_readlinkat+0x7d/0x340 fs/stat.c:576
 __do_sys_readlink fs/stat.c:613 [inline]
 __se_sys_readlink fs/stat.c:610 [inline]
 __x64_sys_readlink+0x47/0x60 fs/stat.c:610
 x64_sys_call+0x2af1/0x3000 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff8881006ac6c0 of 4 bytes by task 6380 on cpu 0:
 d_set_mounted+0xff/0x160 fs/dcache.c:1487
 get_mountpoint+0x197/0x370 fs/namespace.c:903
 attach_recursive_mnt+0x115/0x15d0 fs/namespace.c:2579
 graft_tree+0xf0/0x100 fs/namespace.c:2816
 do_loopback+0x230/0x2b0 fs/namespace.c:2998
 path_mount+0x401/0xbc0 fs/namespace.c:4016
 do_mount fs/namespace.c:4035 [inline]
 __do_sys_mount fs/namespace.c:4224 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4201
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4201
 x64_sys_call+0x2cca/0x3000 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6380 Comm: syz-executor Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
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