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BUG: KCSAN: data-race in __dentry_kill / fast_dput

write to 0xffff8881253b8a90 of 8 bytes by task 1261 on cpu 1:
 __d_drop fs/dcache.c:509 [inline]
 __dentry_kill+0x135/0x4a0 fs/dcache.c:601
 dput+0x54/0xc0 fs/dcache.c:845
 handle_mounts fs/namei.c:1554 [inline]
 step_into+0x21a/0x800 fs/namei.c:1839
 walk_component+0x164/0x230 fs/namei.c:2007
 lookup_last fs/namei.c:2458 [inline]
 path_lookupat+0x10a/0x2a0 fs/namei.c:2482
 do_o_path+0x44/0x120 fs/namei.c:3769
 path_openat+0x1a2c/0x1d40 fs/namei.c:3791
 do_filp_open+0xf6/0x200 fs/namei.c:3825
 do_sys_openat2+0xab/0x110 fs/open.c:1404
 do_sys_open fs/open.c:1419 [inline]
 __do_sys_openat fs/open.c:1435 [inline]
 __se_sys_openat fs/open.c:1430 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1430
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff8881253b8a90 of 8 bytes by task 1260 on cpu 0:
 hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
 d_unhashed include/linux/dcache.h:341 [inline]
 retain_dentry fs/dcache.c:686 [inline]
 fast_dput+0x62/0x2b0 fs/dcache.c:782
 dput+0x24/0xc0 fs/dcache.c:839
 handle_mounts fs/namei.c:1554 [inline]
 step_into+0x21a/0x800 fs/namei.c:1839
 open_last_lookups fs/namei.c:3588 [inline]
 path_openat+0x10da/0x1d40 fs/namei.c:3795
 do_filp_open+0xf6/0x200 fs/namei.c:3825
 do_sys_openat2+0xab/0x110 fs/open.c:1404
 do_sys_open fs/open.c:1419 [inline]
 __do_sys_openat fs/open.c:1435 [inline]
 __se_sys_openat fs/open.c:1430 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1430
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0xffff888237483318 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1260 Comm: syz-executor.4 Not tainted 6.8.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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