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BUG: KCSAN: data-race in __d_drop / fast_dput

write to 0xffff888107a6b850 of 8 bytes by task 3391 on cpu 0:
 __d_drop+0x14d/0x240 fs/dcache.c:576
 __dentry_kill+0x122/0x460 fs/dcache.c:668
 finish_dput+0x2b/0x200 fs/dcache.c:879
 dput+0x52/0x60 fs/dcache.c:928
 lookup_open fs/namei.c:4461 [inline]
 open_last_lookups fs/namei.c:4549 [inline]
 path_openat+0x1155/0x23c0 fs/namei.c:4793
 do_filp_open+0x15d/0x280 fs/namei.c:4823
 do_sys_openat2+0xa6/0x150 fs/open.c:1430
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1447
 x64_sys_call+0x2b07/0x3000 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888107a6b850 of 8 bytes by task 3380 on cpu 1:
 hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
 d_unhashed include/linux/dcache.h:366 [inline]
 retain_dentry fs/dcache.c:753 [inline]
 fast_dput+0x5f/0x2c0 fs/dcache.c:849
 dput+0x24/0x60 fs/dcache.c:924
 end_dirop fs/namei.c:2898 [inline]
 end_creating include/linux/namei.h:126 [inline]
 end_creating_path fs/namei.c:4931 [inline]
 do_mknodat+0x2c2/0x4f0 fs/namei.c:5062
 __do_sys_mknodat fs/namei.c:5080 [inline]
 __se_sys_mknodat fs/namei.c:5077 [inline]
 __x64_sys_mknodat+0x5e/0x70 fs/namei.c:5077
 x64_sys_call+0x2b33/0x3000 arch/x86/include/generated/asm/syscalls_64.h:260
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff88823771cbd0 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3380 Comm: syz.6.20188 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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