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BUG: KCSAN: data-race in __follow_mount_rcu / d_set_mounted

read to 0xffff888100406600 of 4 bytes by task 9151 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+0x953/0xde0 fs/namei.c:-1
 path_lookupat+0x53/0x4c0 fs/namei.c:2812
 filename_lookup+0x18f/0x390 fs/namei.c:2842
 kern_path+0x3b/0xf0 fs/namei.c:3036
 lookup_bdev+0x66/0x170 block/bdev.c:1268
 get_tree_bdev_flags+0x59/0x300 fs/super.c:1862
 get_tree_bdev+0x1f/0x30 fs/super.c:1906
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5897
 vfs_get_tree+0x57/0x1d0 fs/super.c:1943
 fc_mount fs/namespace.c:1282 [inline]
 do_new_mount_fc fs/namespace.c:3910 [inline]
 do_new_mount+0x288/0x730 fs/namespace.c:3986
 path_mount+0x4ad/0xb90 fs/namespace.c:4337
 do_mount fs/namespace.c:4350 [inline]
 __do_sys_mount fs/namespace.c:4565 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4542
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4542
 x64_sys_call+0xc3b/0x2550 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff888100406600 of 4 bytes by task 9154 on cpu 0:
 d_set_mounted+0x119/0x190 fs/dcache.c:1621
 get_mountpoint+0x197/0x380 fs/namespace.c:948
 attach_recursive_mnt+0x1ea/0x17c0 fs/namespace.c:2676
 graft_tree fs/namespace.c:2940 [inline]
 do_add_mount fs/namespace.c:3897 [inline]
 do_new_mount_fc fs/namespace.c:3929 [inline]
 do_new_mount+0x64f/0x730 fs/namespace.c:3986
 path_mount+0x4ad/0xb90 fs/namespace.c:4337
 do_mount fs/namespace.c:4350 [inline]
 __do_sys_mount fs/namespace.c:4565 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4542
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4542
 x64_sys_call+0xc3b/0x2550 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 9154 Comm: syz.0.1038 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
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