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BUG: KCSAN: data-race in __d_drop / fast_dput

write to 0xffff8881004b8850 of 8 bytes by task 22070 on cpu 0:
 __d_drop+0x14d/0x240 fs/dcache.c:585
 __dentry_kill+0x125/0x4d0 fs/dcache.c:716
 finish_dput+0x2b/0x200 fs/dcache.c:927
 dput+0x52/0x60 fs/dcache.c:976
 handle_mounts fs/namei.c:1748 [inline]
 step_into_slowpath+0x38c/0x4c0 fs/namei.c:2100
 step_into fs/namei.c:2148 [inline]
 walk_component fs/namei.c:2284 [inline]
 link_path_walk+0x974/0xe30 fs/namei.c:2652
 path_openat+0x1c6/0x2050 fs/namei.c:4854
 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 0xffff8881004b8850 of 8 bytes by task 22069 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
 handle_mounts fs/namei.c:1748 [inline]
 step_into_slowpath+0x38c/0x4c0 fs/namei.c:2100
 step_into fs/namei.c:2148 [inline]
 walk_component fs/namei.c:2284 [inline]
 link_path_walk+0x974/0xe30 fs/namei.c:2652
 path_openat+0x1c6/0x2050 fs/namei.c:4854
 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

value changed: 0xffff888237959ea0 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 22069 Comm: syz.7.4156 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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