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BUG: KCSAN: data-race in __d_drop / fast_dput

write to 0xffff8881184e5e50 of 8 bytes by task 22964 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
 handle_mounts fs/namei.c:1748 [inline]
 step_into_slowpath+0x38c/0x4c0 fs/namei.c:2101
 step_into fs/namei.c:2149 [inline]
 walk_component fs/namei.c:2285 [inline]
 lookup_last fs/namei.c:2780 [inline]
 path_lookupat+0x330/0x500 fs/namei.c:2804
 do_o_path+0x47/0x140 fs/namei.c:4801
 path_openat+0x1d15/0x2050 fs/namei.c:4823
 do_file_open+0x259/0x290 fs/namei.c:4861
 do_sys_openat2+0x94/0x130 fs/open.c:1366
 do_sys_open fs/open.c:1372 [inline]
 __do_sys_open fs/open.c:1380 [inline]
 __se_sys_open fs/open.c:1376 [inline]
 __x64_sys_open+0xe6/0x110 fs/open.c:1376
 x64_sys_call+0x14b9/0x3020 arch/x86/include/generated/asm/syscalls_64.h:3
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881184e5e50 of 8 bytes by task 22965 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
 handle_mounts fs/namei.c:1748 [inline]
 step_into_slowpath+0x38c/0x4c0 fs/namei.c:2101
 step_into fs/namei.c:2149 [inline]
 walk_component fs/namei.c:2285 [inline]
 lookup_last fs/namei.c:2780 [inline]
 path_lookupat+0x330/0x500 fs/namei.c:2804
 filename_lookup+0x190/0x390 fs/namei.c:2833
 user_path_at+0x3e/0x100 fs/namei.c:3612
 do_mount fs/namespace.c:4156 [inline]
 __do_sys_mount fs/namespace.c:4348 [inline]
 __se_sys_mount+0x25b/0x2e0 fs/namespace.c:4325
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4325
 x64_sys_call+0x2d61/0x3020 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff888237946a48 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 22965 Comm: syz.2.5923 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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