syzbot

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BUG: KCSAN: data-race in __d_drop / fast_dput

write to 0xffff888107a6ad90 of 8 bytes by task 8396 on cpu 0:
 __d_drop+0x14d/0x240 fs/dcache.c:585
 d_invalidate+0x50/0x1d0 fs/dcache.c:1768
 lookup_fast+0x296/0x320 fs/namei.c:1880
 lookup_fast_for_open fs/namei.c:4548 [inline]
 open_last_lookups fs/namei.c:4582 [inline]
 path_openat+0x436/0x2050 fs/namei.c:4855
 do_file_open+0x16c/0x290 fs/namei.c:4887
 do_sys_openat2+0x94/0x130 fs/open.c:1364
 do_sys_open fs/open.c:1370 [inline]
 __do_sys_openat fs/open.c:1386 [inline]
 __se_sys_openat fs/open.c:1381 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1381
 x64_sys_call+0x1e39/0x3020 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888107a6ad90 of 8 bytes by task 8393 on cpu 1:
 hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
 d_unhashed include/linux/dcache.h:379 [inline]
 retain_dentry fs/dcache.c:801 [inline]
 fast_dput+0x5f/0x2c0 fs/dcache.c:897
 dput+0x24/0x60 fs/dcache.c:972
 end_dirop fs/namei.c:2952 [inline]
 end_creating include/linux/namei.h:123 [inline]
 end_creating_path fs/namei.c:4990 [inline]
 filename_mknodat+0x2cb/0x450 fs/namei.c:5184
 __do_sys_mknodat fs/namei.c:5201 [inline]
 __se_sys_mknodat+0x38/0xf0 fs/namei.c:5197
 __x64_sys_mknodat+0x55/0x70 fs/namei.c:5197
 x64_sys_call+0x312/0x3020 arch/x86/include/generated/asm/syscalls_64.h:260
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff8882375f0d68 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 8393 Comm: syz.4.1238 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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