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BUG: KCSAN: data-race in __dentry_kill / fast_dput

write to 0xffff888106971a90 of 8 bytes by task 6606 on cpu 0:
 __d_drop fs/dcache.c:521 [inline]
 __dentry_kill+0x13e/0x4c0 fs/dcache.c:613
 dput+0x5c/0xd0 fs/dcache.c:857
 handle_mounts fs/namei.c:1579 [inline]
 step_into+0x21a/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
 user_path_at+0x3c/0x110 fs/namei.c:3016
 do_mount fs/namespace.c:3844 [inline]
 __do_sys_mount fs/namespace.c:4055 [inline]
 __se_sys_mount+0x248/0x2d0 fs/namespace.c:4032
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4032
 x64_sys_call+0x203e/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:166
 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 0xffff888106971a90 of 8 bytes by task 6605 on cpu 1:
 hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
 d_unhashed include/linux/dcache.h:354 [inline]
 retain_dentry fs/dcache.c:698 [inline]
 fast_dput+0x65/0x2c0 fs/dcache.c:794
 dput+0x24/0xd0 fs/dcache.c:851
 handle_mounts fs/namei.c:1579 [inline]
 step_into+0x21a/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
 user_path_at+0x3c/0x110 fs/namei.c:3016
 do_mount fs/namespace.c:3844 [inline]
 __do_sys_mount fs/namespace.c:4055 [inline]
 __se_sys_mount+0x248/0x2d0 fs/namespace.c:4032
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4032
 x64_sys_call+0x203e/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:166
 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: 0xffff8882377cd520 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 6605 Comm: syz.0.1054 Tainted: G        W          6.12.0-rc1-syzkaller-00031-ge32cde8d2bd7 #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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