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BUG: KCSAN: data-race in __d_instantiate / step_into

read-write to 0xffff88810649c9c0 of 4 bytes by task 3258 on cpu 0:
 __d_instantiate+0x2d5/0x3c0 fs/dcache.c:1869
 d_instantiate+0x59/0x80 fs/dcache.c:1894
 shmem_symlink+0x36a/0x3a0 mm/shmem.c:3847
 vfs_symlink+0xca/0x1d0 fs/namei.c:4615
 do_symlinkat+0xe3/0x350 fs/namei.c:4641
 __do_sys_symlink fs/namei.c:4662 [inline]
 __se_sys_symlink fs/namei.c:4660 [inline]
 __x64_sys_symlink+0x50/0x60 fs/namei.c:4660
 x64_sys_call+0x2819/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:89
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810649c9c0 of 4 bytes by task 2967 on cpu 1:
 __follow_mount_rcu fs/namei.c:1511 [inline]
 handle_mounts fs/namei.c:1562 [inline]
 step_into+0xe7/0x810 fs/namei.c:1891
 walk_component+0x169/0x230 fs/namei.c:2059
 lookup_last fs/namei.c:2556 [inline]
 path_lookupat+0x10a/0x2b0 fs/namei.c:2580
 filename_lookup+0x127/0x300 fs/namei.c:2609
 do_readlinkat+0x89/0x210 fs/stat.c:537
 __do_sys_readlink fs/stat.c:574 [inline]
 __se_sys_readlink fs/stat.c:571 [inline]
 __x64_sys_readlink+0x47/0x60 fs/stat.c:571
 x64_sys_call+0x13c3/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000008 -> 0x00600008

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2967 Comm: udevd Tainted: G        W          6.12.0-rc1-syzkaller-00257-g2f91ff27b0ee #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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