syzbot

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BUG: KCSAN: data-race in __follow_mount_rcu / d_set_mounted

read to 0xffff8881006b9a80 of 4 bytes by task 2986 on cpu 1:
 __follow_mount_rcu+0x156/0x2a0 fs/namei.c:1714
 handle_mounts fs/namei.c:1740 [inline]
 step_into_slowpath+0x30c/0x4c0 fs/namei.c:2104
 step_into fs/namei.c:2152 [inline]
 walk_component fs/namei.c:2288 [inline]
 link_path_walk+0x947/0xdd0 fs/namei.c:-1
 path_lookupat+0x53/0x4c0 fs/namei.c:2812
 filename_lookup+0x18f/0x390 fs/namei.c:2842
 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+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff8881006b9a80 of 4 bytes by task 3304 on cpu 0:
 d_set_mounted+0xff/0x160 fs/dcache.c:1605
 get_mountpoint+0x197/0x370 fs/namespace.c:898
 attach_recursive_mnt+0x11a/0x1700 fs/namespace.c:2588
 graft_tree+0xf0/0x100 fs/namespace.c:2845
 do_loopback+0x247/0x480 fs/namespace.c:3028
 path_mount+0x3ea/0xb90 fs/namespace.c:4155
 do_mount fs/namespace.c:4174 [inline]
 __do_sys_mount fs/namespace.c:4390 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4367
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4367
 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+0x136/0x3c0 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: 3304 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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