syzbot

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BUG: KCSAN: data-race in __follow_mount_rcu / d_set_mounted

read to 0xffff8881006b7780 of 4 bytes by task 3004 on cpu 0:
 __follow_mount_rcu+0x15f/0x2b0 fs/namei.c:1709
 handle_mounts fs/namei.c:1735 [inline]
 step_into_slowpath+0x30c/0x4c0 fs/namei.c:2101
 step_into fs/namei.c:2149 [inline]
 walk_component fs/namei.c:2285 [inline]
 link_path_walk+0x974/0xe30 fs/namei.c:2647
 path_lookupat+0x8c/0x500 fs/namei.c:2803
 filename_lookup+0x190/0x390 fs/namei.c:2833
 do_readlinkat+0x74/0x2f0 fs/stat.c:571
 __do_sys_readlink fs/stat.c:605 [inline]
 __se_sys_readlink fs/stat.c:602 [inline]
 __x64_sys_readlink+0x47/0x60 fs/stat.c:602
 x64_sys_call+0x2b51/0x3020 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff8881006b7780 of 4 bytes by task 3324 on cpu 1:
 d_set_mounted+0xff/0x160 fs/dcache.c:1487
 get_mountpoint+0x197/0x370 fs/namespace.c:897
 attach_recursive_mnt+0x115/0x15d0 fs/namespace.c:2583
 graft_tree+0xf0/0x100 fs/namespace.c:2827
 do_loopback+0x24b/0x490 fs/namespace.c:3024
 path_mount+0x401/0xbc0 fs/namespace.c:4153
 do_mount fs/namespace.c:4172 [inline]
 __do_sys_mount fs/namespace.c:4361 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4338
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4338
 x64_sys_call+0x2d61/0x3020 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3324 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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